Biology 24/7

homothallism and heterothallism in fungi

2026-02-01T14:12:00.000+05:30

HOMOTHALLISM IN FUNGI

The condition in which one individual originating from a single asexual spore is capable of farming zygospore (zygote) independently is known as homothallism. A few species of achlya such as Achlya racemosa are homothallic. In homothallic species two types of sex organs i.e., anthredia and ogonia are developed on the same mycelium.

In ACHLYA racemosa, the oogonia are developed at the tips either of short lateral hyphae or on the main hypha. The tip of the female branch swells up to form a sac like oogonial initial . subsequently, the swollen structure is cut off by a cross wall at its base. It is the oogonium.

The anthredia are developed on thin hyphal branches which arises from the female hypha. The tip of the anthredial hypha enlarges. A number of nuclei and some cytoplasm migrated to the inflated tip. The swollen portion is then cut by a cross wall. It is the anthrediem.

HETROTHALLISM IN FUNGI

Hetrothallism may be defined as the condition in which zygospore ( zygote) formation takes place only when mycelia arising from sexual spores of two genetically different mating types, (+) and the (-), are allowed to intract. The term hetrothallism was first coined by A.F. Blakeslee in 1994.

On the basis of nature of the mating types, hetrothallism may be of the following types-

· Morphological hetrothallism :

Morphological hetrothallism may be defined as the condition when the morphologically different male and female sex organs are produced in two closely associated mycelia. The two sex organs or gamets are so morphologically dissimiliar that it is easier to term one of them as male and the other as female. Some of the examples of hetrothallic fungi are – Achyla ambisexualis, A, bisexualis, Phytophthora palmivora, Peronospora parasitica, etc.

· Physiological hetrothallism :

PPhysiological hetrothallism, the interacting thallis differ in mating type or incompatibility irrespective of the presence or absence of sex organs or gamets. This means that sexual reproduction takes place by two morphologically different hyphae. The gametangia or gametes do not show morphological differentiation but physiologically they behave differently.

Intellectual property rights notes

2022-12-03T23:32:00.001+05:30

Intellectual property rights notes

Intellectual property rights are legal rights, which result from intellectual activity in industrial, scientific, literary and artistic fields. These rights safeguard creators and other producers of intellectual goods and services by granting them certain limited rights to control their use.

Types/Tools of Intellectual property rights

Patents
Trademarks
Copyright and related rights
Geographical indications
Industrial design
Trade secrets
Layout design for integrated circuits
Protection of new plant variety

Patent

It provides protection for the invention to the owner of the patent. The protection is granted for a limited periods, i.e 20 years.

A patent owner has the rights to decide who may or may not use the patented invention for the period in which the invention is protected. The patent owner may give permission to, or license, other parties to use the invention on mutually agreed terms.

Trademarks

It may be one or a combination of words, letters, and numerals. They may consists of drawings, symbols, three dimensional signs such as the shape and packaging of goods, audible signs such as music or vocal sounds, fragrances, or colours used as distinguishing features.

It helps consumes identify and purchase a product or service because it's nature and quality, indicated by its unique trademark, meets their needs.

Copyright and related rights

Copyright is a legal term describing rights given to creators for their literary and artistic works. The kinds of works covered by copyright include, literary works such as novels, poems, plays, reference work, newspaper and computer programs; paintings, drawings, photographs and sculpture; architecture; and advertisements.

Geographical indications (G.I)

Geographical indications are signs used on goods that have a specific geographical origin and possess qualities or a reputation that are due to that place of origin. Agricultural products typically have qualities that derive from their place of production and are influenced by specific local factors, such as climate and soil.

A geographical indications points to a specific place that determines the characteristics qualities of the product that originates theirin. Place of origin may be a village or town, a region or a country.

Industrial Designs

Industrial design refer to creative activity, which result in the ornamental or formal apperance of a product.

The essential purpose of design law it to promote and protect the design element of industrial production.

Trade Secrets

It may be confidential business information that provides an enterprises a competitive edge may be considered a trade secret. Usually these are manufacturing or industrial secrets. These includes sales methods, distribution methods, consumer profiles, advertising strategies, lists of suppliers and clients and manufacturing process.

Layout design for integrated circuits

The aim of the semiconductor integrated circuit layout design Act 2000 is to provide protection of intellectual property rights (IPR) in the area of semiconductor integrated circuits layout designs and for matters connected there with or incidental thereto.

Protection of new plant variety

The objective of this act is to recognise the role of farmers as cultivators and conserves and the contribution of traditional, rural and tribal communities.

The plant variety protection and farmers rights act 2001 was enacted in india to protect the new plant variety; the act has come into force on30-10-2005 through authority. Initially 12 crop species have been identified for regt. I.e Rice, Wheat, Maize, Sorghum, Pearl millet, Chickpea, Green gram, Black gram, Lentil kidney bean etc. India has opted for sui-generic system instead of patents for protecting new plant variety.

downy mildew of grapes

2021-08-03T13:16:00.002+05:30

downy mildew of grapes

Downy mildew of grapes distributed worldwide where the grapes are grown in humid condition.
The Plasmopora viticola attacks on fruits and leaf of the grapes plants and also cause dwarfing and killing the young shoots.
The downy mildew of grapes is caused by Plasmopora viticola.

downy mildew symptoms

On the upper surface of the bay leaf developed yellowish gray spot from the lower surface of the spores downy growth of fungus appear these nacrotic areas may causes.
The leaf of the grapes turn to become brown and the infected leaf may finally die. Barriers turn brown and may also be attacked.
Mildew pathogen is not indused storage decay.

Causal Organism of downy mildew of grapes

Plasmopora viticola
The conidiophore branches at the right angle and are in irregularly spaced.

Intercellular space in mycelium has mycelium ranifers in it and sets haustoria globose into infected tissue.
Through One stoma 4-6 sporangiophores arise each sporangiophores producing 4-6 branches nearly right angle to make branches, after that 2-3 secondary branches are produce from each such branches.
Sporangia germinates through resting spores or zoospores are produce as a result of fertilization between Anthredia and oogonia.

Disease Cycle of downy mildew of grapes

The fungus over twinter through. Oospores on the infected plant. Oospores germinates at a temp range of 20°c to 25°c penetration take place through stomata on lower surface of the leaves. For the production of sporangial the incubation periods is about 5-8 days after infection, depending upon the humidity and the temperature

Downy mildew of grapes life cycle

Sporangia is responsible for the secondary infection and this is germinates by the means of zoospore.

Controls of downy mildew of grapes

The infected leaves of sanetary precaution and the fallen things should be destroyed.
Use resistance variety of crops.
The most commonly used spray of fungicides are as follows; Biltox 50,Captan, Bordeaux mixture etc

Paddy blast | Paddy Blast Disease

2021-06-25T22:37:00.000+05:30

Paddy Blast | Paddy Blast Disease

Class	Deuteromycetes
Sub-Class	Hyphomycetede
Order	Moniliales
Family	Monoliolose
Pathogen	Pyricularia oriza

Symptoms

Symptoms on leaf appear on small spindal shape spot with brown margine. The center of the spot is whitish grow. Such spores like appear on the collum, collum nodes and glumes.

The neck become shrivelled and covered with gray fluphy Mycelium and bends down due to Waite of the year.

The infected grain are also shrivelled.

Causal Organism

Pyricularia oriza
Mycelium consists of septate gray to olivesious hypha mostely located in leisons.
Conidiospores are haline monoseptate dentipelate and produced through stomata or by repturing the cuticle. Conidia are produce in succession one at a time at the tips of conidiospores. Conidia are biseptate, haline olivasious pyriform to obclavate with rounded base and narrow towards the tip.

Disease Cycle

Sori of primary inoculum is not definitely known.

The initiation occur through the conidia Mycelium can survive in infected Structure for 1 or 2 year.

Under dry condition bud during humid condition. It is generally destroy due to microbial activity.

The fungus also infected in the seeds during the stage but the seed borne inoculum do not succeed because high soil temperature in May and June.

Controls

Field sanitation
Seed treatment
The folior spray copper fungicide are effecting in controlling the blast in some variety.
Use of resistance variety CO-4, CO-25, CO-26 are the variety found to be highly resistant variety to blast disease.

Tikka disease

2021-06-25T19:22:00.000+05:30

Tikka disease of groundnut

Class	Deuteromycetes
Sub-Class	Hypemycitidae
Order	Moniliales
Family	Dematiaceae
Pathogen	Cercosporidium personatum

Symptoms

The disease appears as two distinct type of leaf spots cause by two species of Cercospora.
The groundnut leaf is infected by Cercospora archidicola show circular to irregular 1 to 10mm spores with a raddish brown to a black nacrotic area.
Spots appears as a result of infection by Cercospora personata are smaller circular and dark brown to black in colour which enlarges upto about, 1-10 mm in diameter.

Source Biology reader

Causal Organism

Cercosporidium personatum earlier known as Cercospora personatum.
Perfect stage Mycosphaerella Berkeley Jenkins.
Cercospora archidicola perfect stage Mycosphaerella.
Mycellium is restricted mostly in lesons first appears be intercellular which later turn in to intercellular.
Haustoria are produce.
Conidiospores are developed from Brown to black colour stroma rapturing the Epidermis.
Conidiophore is one to septate un-branched measuring 54-60 microne, heaving know joints.
Conidium formation, start at the tip of conidiophore.
Conidium is haline pole yellow to dark filly form and multi celled (4-12 septae) with rounded or truncate base and subaccute tip.

Disease Cycle

Primary infection occurs through conidia carried over the plants devaries or by seeds.
The fungus spread through the air born conidia the role of perfect stage in perpeturing the disease in India is not fully known.

Controls

Field sanitation
Folior spray - Diethoin M²², Fygol QE, Diethain Z78.
Use resistance variety.

powdery mildew of grapes

2021-03-21T01:15:00.000+05:30

Powdery mildew of grapes

Class	Ascomycetes
Sub-Class	Hymenomycetidae
Order	Erysiphales
Family	Erysiphaceae
Pathogen	Uncinula necator
Host plant	Grapes

The disease powdery mildew of grapes is world-wide in distribution. In India the disease powdery mildew of grapes appears in epidermic form periodically after some year causing great loose to the crop of grapes.

powdery mildew symptoms

Small white patch appear on the follier parts which in advance stage cover whole leaves surface flower, fruits and stem parts.
The infection result in clorosis malformation and defoliation of leaves, dwarfing by the host plant as well as deformed barriers.

powdery mildew of grapes

Causal Organism of powdery mildew of grapes

Uncinula necator
Conidia are oval and are produce on errect conidiospores.

Disease Cycle of powdery mildew of grapes

Fungus is an obligate parasites.
Disease Cycle is not well understand.
It is presumed that in India condition pathogen survives the off season through conidia and hyphal mats on plants debris.

Life cycle of powdery mildew of grapes

Powdery mildew treatment

Predically spray of Bordaux mixture prior to blossming and before the ripining of fruits is recommended sulphur distings is also found effecting.

Rust of Linseed (With Diagram)

2021-03-20T17:20:00.002+05:30

Rust of Linseed or Linum (Rust of flax)

Class	Basidiomycetes
Sub-Class	Teliomycetidae
Order	Uridenales
Family	Melamsporaceae
Pathogen	Melampsora lini

The disease have been reported from about 12 species of Linum.

Linseed Rust

Symptoms of rust of linseed

The disease appears as bright orange pastules of Uridia of leaf stem and flower part.
Telia formed mostely on the stem and are reddish brown in colour.

The soil are covered by Epidermis and appear like a crust.

Rust of Linum

Rust of linseed causal organism

Melampsora lini
The disease is autoscious or long cycled rust producing sporangia aceredia, uredia and Telia on the line lower side of leaves.
The acia are of orange yellow colour and are abundant on the lower side of leaves.
Telidiospores are subepidermal, cylindrical one, called sessile and reddish brown in colour with measurements of 46 to 80 micro × 8 to 10 micro and are closely packed in a layer.

Disease Cycle of rust of linseed

The primary infection is caused by Uridiospores and teliospores. It is also presumed that Uridiospores may also survive in some wild lini seed plant like Linum mysorens.

Disease cycle of Rust of Linseed

Rust of linseed control

Sanitation of disesase crop debris
Distraction of cultration host
Use of resistance variety.

Bunt of wheat | Karnal bunt of wheat

2021-03-20T00:55:00.000+05:30

Bunt of wheat 🌾

This smut disease also called stinking smuts of wheat are widely distributed in all wheat growing areas of the world.
They effect plant by destroying the constrent of infected kernels and replacing them with the spores of fungus.
Bunt causes losses in grain yield.

Symptoms of bunt of wheat 🌾

Affected plants are usually shorter then healthy one.
The colour of the plant may changed to bluish green to greenish green.
The most pronounced symptoms however when the head of infected plants emerged.
Infected kernels are shorter and thicker and greyish brown then normal golden yellow or red.

These are usually full of shoot black, powdery mass of spores, the teliospores that give a distil smell of decay fish.

Bunt of wheat

Causing organisms of bunt of wheat 🌾

The disease caused by Telia carris, Telia foetida and Telia contraversa.
They mycellium is hyaline and during sporulation most cells are transformed into sperical, brownish teliospore.
Open the germination each spore produces 8 to 16 cells.
These fuse in pairs forming 'H' shaped structures.
Each secondary sporedium open germination produces dikaryotic Mycelium that infects the plants.
After systematic development through the plant. The Mycelium again forms teliospores.
The fungus survives as teliospores on contaminated wheat kernels and in soil.
When contaminated seed in shown teliospores germinate with the young seedings and form basidia primary sporedia and secondary sporedia.
The dikaryotic Mycelium formed after germination of Secondary sporedia, penitrate of the young seedlings directly.

It grows interactly and invoices developing leaves and growing point of the plant.
The Mycelium grows with these growing points when heads are form on plant the Mycelium invade all part of it even before the head emerge out of the boot.
These spores are covered by pericarp or the kernels forming a covering around the spore mass.
They break and release their spore during harvest or thorting.

Karnal Bunt of wheat 🌾

Karnal bunt of wheat

Reported in 1931- by Mitra from Karnal, india
Sever in Trai & northern parts of country

Symptoms :

Symptoms appear in ear
Not all ear in a stool affected
Not all grains in a ear
Not all grain but partially
So called partial bunt

Controls of bunt of wheat 🌾

Use of resisted variety.
Sanitation that is burning of straw and other infected part.
Crop rotation to avoid infection by soil borne teliospore.

Cultural practices that is modification of soil temperature and motiour.
Seed treatment to aliminate seed born teliospore.
Hexa chlorobenzene (carboxine) Thiram, Chloranil.

Black stem rust of wheat

2021-03-20T00:26:00.001+05:30

Black Stem Rust of Wheat

This rust usually appears late in season. It is often not seen until March in northern India by the eating time of crops.

Black stem rust of wheat 🌾

Symptoms Of Black Stem Rust of wheat

The rust appears in the form of elongated raddish brown pastules ( Uridia ).
Primarily on the stem and followed by the leaf sheath and leaf.
Stem is most severally attacked.
The Uridia frequently merged with each other soon brust exposing the brown powder of uridiospores surrounding by reptured Epidermal fringes.

Another kinds of pastules ( Telia ) develop letter in the same source or independently.
Telia are darker and by this time pastules channel from brown to almost black colour.
These are also most promenent culms followed by leaf sheath and leaf.

Causal Organism of black stem rust of wheat :

Black stem rust is caused by Puccinia graministtritci.
The hypha in wheat leafs small round or branched but haustoria from this Mycelium Uridiospores develop in Uredospores beneath the Epidermis.
Each Uredospores is oval staked brown body 25 to 30 × 70 -20mm.
Single Uridiospores cell with echinulate exospore.
These are 4 germpore along and equatorial band.
As host Epidermis reptured, Uridiospores are disseminated by wind.
They germinated on healthy parts of plants causing Secondary infection.
Telia however are like uredia more frequent on stem.
Telia are oblong to liniour dark brown to black exposed through the rifted Epidermis.
Each teliospore is staked two celled with a thick smooth wall.
The apex is round or pointed.
Each cell has a germpore.
Teliospore under go a period of rust four several month.
In India these spores are unable to survive the hot summer temperature following the harvesting the crop.
If condition are suitable each cell of teliospore germinate to farm a four cell promiulium from each promiulium 4 haploid basidiospores are formed in stigma.
Berberis vulgaris the common barberry growing in heals is the alternate host.
On germination basidiospores give rise to haploid Mycelia inside bar berry leaf.
This Mycelium develop special structures on both side of leaf of barberry.
Puccinia are flasked shaped Structure on the upper surface.
Inside it are Spermatia sexual fusion occurs between Spermatia and flexous hypha of pycinidia of opposite stains.
The dicariotic Mycelium thus developed then formed another types a Structure accia. On the lower surface of leaf.

Accia are yellow cup shaped respecticals inclosed by peridium.
Each aecial cup contains chains of aeciospores.
The aeciospores are yellow echinulate and with 6 germspore.
Aeciospore does infect wheat leafs through stomata.
The cycle may be completed with the Uridiospores only and it usually occur in India.

Frequently asked questions

Q-1. Black rust of wheat is caused by ?

Ans- Black rust of wheat is caused by Puccinia graministtritci.

Q-2. What is black stem rust ?

Ans- Black stem rust is a plant disease caused by a fungus Puccinia graminis. It's farm black patches on the stem of wheat.

Q-3. What cause rust in wheat?

Ans- Answer this question in comment box.

Red rot of Sugarcane | Causal organism

2021-03-20T00:08:00.003+05:30

Red rot of Sugarcane | Causal organism

Red rot is a serious disease of sugarcane is sub-tropical parted of the world.
In India the disease attacks canes in field.
In the first time it occurred in U.P & Bihar during 1939-1940 and 1946-1947.

Red rot of sugarcane symptoms -

The disease appear on all above ground part but stems and midrib arises of leafs are most affected in earlier stage dropping of leaf and the loss of their colour can be seen in the field
Later the cane also starts developing the symptoms.
The canes are completely rotted within the wind losses.
It's natural bright colour becomes Dule and shrinks at the nodes.
On the midrib of leafs infection origenates as a dark raddish area.

Red rot of sugarcane

Red rot of sugarcane is caused by

The disease cause by Colletotrichum falcatum.
The Mycelium once inside the host grows rapidly.

Hypha are cylendrical branched septate colourless inter and intra cellular.
The hypha produce the large no of chlamydospores in the pith.
These can survive in soil for a long time.
The hypha collect beneath the Epidermis and form a strong of den cell.
Conidia are disseminated by wind rain or water of irregstion rain drops, splash and insects.
They germinates soon presence of water and may spread the disease by new healthy tissue of host plant.

Controls of Red rot of sugarcane

Field sanitation
Use of healthy sets

Crop rotation should be used
Use of resistance varieties

Smut of Sugarcane | Pests & Diseases

2021-03-19T23:35:00.002+05:30

Smut of Sugarcane | Pests & Diseases

This is an important disease of sugarcane besides India the disease has been reported from other sugarcane growing areas of the world's.
In India the pathogen also attacks Saccharum sp. Which may be a Collateral host.

Symptoms of smut of sugarcane

In the field disease plant may be easily recognised by their long whipe like black short much covered on it self.
Firstly the powdery mass of teliospore on their while like Structure is contain by a fine membrane that reptures later exposing the black mass of teliospore.
The lateral shoots developing from the eyes on this infected cone may be also developed similiar structures after infection the damage of growing point of infected cone results into sprouting of eyes which produce lateral smutted whips.
The first symptoms are showing during may and June and second during october, November.

Smut of sugarcane

Smut of sugarcane causal organism

The disease is cause by Ustilago scitaminea

The teliospore are sperical, smooth, light brown in colour.
They are deposited at the function of leaf and sheath, from where they travel down the sheath and reach the model region and young eyes.
In the presence of moisture at the base of sheath, the teliospore germinates easily to produce promycelium and sporedia.
The sporedia are elongated unicellular and germinates to form hypha.
Promycelium some time instead of forming sporedia gives rise directly to branched bypha.
The Mycelium is mainly located in the meristem.

Controls of smut of sugarcane

Removal of smutted whips from the field.

To avoid plating of sets from smutted cane.
To avoid cultivation of suspectiable varieties as CO-300, CO-301, CO-311
Use of resistance varieties as CO-285, CO-365, CO-385, CO-499 etc
Disinfected of sets before planting the chemicals used are alcohol 0.25% mercuric chloride 0.17% formaline 1% and some systemic fungicides like vitivox, benlate, bavistin, a hot water treatment is also effected.

Wilt of cotton | Wilt disease of cotton

2021-03-19T23:11:00.001+05:30

Wilt of cotton | Wilt disease of cotton

In India the disease is confined to central part of the country where occur the black cotton soils.
These soils are heavy clay with pH 7.6-7.8.
The disease uncommon to rare in light alkaline or long soils.

Wilt of cotton symptoms

Wilting is characterised by yellowing withering drying of leafs following by drying of entire plant or of some branches.
Often the disease plant has stunted with smaller leaves.
Disease plant may be seen as isolated patches in the field.

Fusarium wilt of cotton

Wilt of cotton causal organism

Wilt of cotton is caused by Fusarium oxysporum, Fusarium vasinfectum
Arial Mycelium white to greyish, white or bluish purple forming a mat on the coller region of stem near the ground lable.
Hypha are interested as well as intercellular.
Hypha run across the cells growing rapidly along the inner wall of xylem vessels.
Conidiospores develops in sporodochia pinnates or even directly on the Mycelium.
Conidiospores are verticulattery branch producing microconidia.
Microconidia are elliptic and unicellular 5-12 × 2-3.5 um which are common.
The disease is soil born and fungus survives on stubbles of disesase plants.
There is also avidence that this is seed born disease.
Infection occurs throught roots.
The fungus enters in 1-3 week old plants and we'll symptoms become visible on 5-6 week old plants.
Secondary infection by conidia is rare.

Cotton wilt disease Management or control

Field sanitation
Crop rotation

Mixed croping
Disease resistance varieties
Amendment of soil with proper amount of nitrogen and potash fertilizer and the micronutrients like zinc then plant will be prevent disease.

Bacterial Leaf Blight of rice

2021-03-11T00:38:00.000+05:30

Bacterial Leaf Blight of rice

Class	Schizomycetes
Order	Eubacteriales
Family	Pseudomonadaceae
Pathogen	Xanthomonas oriza

Symptoms of bacterial leaf blight of rice

Bacterial leaf blight of rice

Water shocked translucent spores appear on the leaves and leaves sheath.
It turn soon to yellow or white in colour.
The leisons may coeasce to form large white bloches.
The disease spread mainly through the vascular bundles and the blight are mainly confined to the leaves.

Causal Organism bacterial leaf blight of rice

Bacterial leaf blight of rice

Xanthomonas oriza
The bacteria is gram rod measuring 0.5 to 0.8 × 1 micro, flagellum capsulate.
The thermal dead point of the pathogen is 53°c.

Disease Cycle of bacterial leaf blight of rice

The mode of Transmission of disease from one session to another is through infected plant.
The pathogen infected the host cell through the wounds and stomata.

Controls of bacterial leaf blight of rice

Seed treatment
Folior spray - Agrimycin.
Field sanitation

Flag smut of wheat

2021-03-11T00:13:00.001+05:30

Flag Smut of wheat

The disesase flag smut of wheat was first deteched in South Australia in 1868. The flag smut of wheat in India was observed in 1918 in the areas now in Pakistan and since then has been reported from punjab, Madhya Pradesh, Himachal Pradesh, Delhi, Rajasthan, Haryana.

Symptoms

Disease (Flag must of wheat) appear on leaf blades sheaths stems, as gray black, pastules of sori.
The server infection may reduction in plant growth and in no of inflorescence.

Flag smut of wheat

Causal Organism of flag smut of wheat

Urocytis tritici
The sporedia are form in tinospore ball, brown fertile spore covered by a layer of sterile peripheral cells.
Each spore is 18-22 micro in diameter.
The spore germinates in situ through promycelium which later produce cylendrical sporidia having a measurements of 12-15 micro into 3-4 micro.

Disease Cycle of flag smut

The disease (flag smut of wheat) is both soil borne as well as externally seed borne.
Infection takes place in selling stage.
Infection is systematic.

Image wikipedia

Controls of flag smut of wheat

Seed treatment, seed dressing, with copper seed sulphate, copper carbonate is the most efficient method in controlling of flag smut of wheat.
Crop rotation, since the disease is soil borne crop rotation for 4-5 year is recommended.
Use of resistance variety. Some variety found resistant to flag Smut of wheat disease.

Apple scab Disease / Cycle / symptoms

2021-03-05T23:03:00.001+05:30

Apple scab disease

Class	Ascomycetes
Sub-Class	Loculoascomycetidae
Order	Pleosporales
Family	Venturiaceae
Pathogen	Venturiaceae inaequales

Apple Scab is rough ended ulsor or crust like on the on the plant parts. Apple scab is reported in those country where apple are grown. It is the most distractive cooled and humid climate.

Apple scab symptoms

First symptoms appear as olive brown spores on young leaf or flower bud.
The spore soon turn to dark brown or black with variety appearance.
As the growing lessons become older the velvaty appearance becomes brown and cracked.
Crakes developed around luisons on the fruits. In reniour infection leaf may become dwarf and curly and eventually fell all.

Pathogen of Apple Scab

Venturiaceae inaequalis
The young Mycelium haline but turn reddish brown with age.
Dencely packed rounded Mycelium cells in several super imposed layer from stroma beneath the host cuticle.
The shape of conidia are variable magening 6-9 micro × 12-20 micro
Plasmogamy takes places through Antheredia and oogonia of compatible stains.
Olive green to brown partially embedded perithecia appear generally in dead leaves.
Such ascocarp are spherical 9-160 micro in diameter slitely pepepliate and ostiole and are surrounded by several setal of 25-75 micro in length.

Apple Scab Disease Cycle

The fungus survives the off season as stromatoid Mycelium in things of infected tree.
The funguses perpetelate sepropectuly on follen leaves and twings.
Ascocarps are ejected forcibly into air and dis aminated by wind heavy ascocarps discharge is reported during the period of rain fall over 5-9 weak optimum temp.
Ascospore germinates is 20°c.
Conidia which are the source of Secondary enoculuon are dependent of water for dispersal and disamination.

Apple scab Disease cycle

Controls

Bordex mixture has been found to successfull control the disesase.
Fungicides like capton glyodine ferban, thirman are recommended as coverspray against late infection.
For ground spray fungicides like elgetol is suggested.

plant hormones and their functions

2020-10-06T23:25:00.001+05:30

plant hormones and their functions

In June 1905, Ernest Starling, a Professor of Physiology at university of London, U.K. first used the word ‘hormone’. In one of the four Croonian lectures on the chemical correlation of the function of body–delivered at the Royal College of Physicians in London. Starling, defined the word, derived from the Greek meaning ‘to arose or excite’, as “the chemical messengers which speeding from cell to cell along blood stream, may coordinate the activities and growth of different parts of the body” (Jamshed R. Tata, 2005).

Initial studies on mechanism of hormone action suggested hormone–enzyme interactions as the basis of a common mode of action. However, by the end of 1950s, there were little enthusiasms and support for this idea.In the early 1940s, Rechimiel Levine had proposed that insulin controlled sugar metabolism by regulating its transport into the cell(s), which led several years later to the concept that protein and smaller peptide(s) signals interact with the cell membrane.

The discovery of cyclic AMP (camp) by Earl Sutherland in 1956 as a ‘second messenger’ of adrenaline and glucagons, followed by the discovery that adenylyle cyclase, the enzyme that synthesize camp, was located in plasma–membrane, further consolidate the view that the cell membranes was major site of action of many hormones.

With the discovery of other molecules, such inositol triphosphate, G Proteins and oncogenes, and the advent of gene cloning and sequencing technologies, it soon became possible to identify, characterize and locate several membrane bound hormone receptors in animals, microbes and plants.

Binding of the ligand to thesereceptors initiates a cascade of protein phosphorylation and dephosphorylation in the cytoplasm, which eventually leads to the biochemical interactions and physiological actions of hormone(s).

Concept Hormones in plants

Plant growth and development involves the integration of many environmental and endogenous signals that, together with the intrinsic genetic program, determine form and functions. Fundamental to this process are several growth regulatory substances collectively called the plant hormones or phytohormones. Decades of biochemical, molecular biological and physiological studies have demonstrated that plants rely on diverse set of hormones that regulate every aspect of their biology.

The degree of specificity and redundancy among plant hormones has long been matter of debate and discussion particularly in the area of growth regulation. Analysis of biosynthetic and signaling mutants, in combination with exogenous hormone applications both in vivo and in vitro have concluded that gibberellins (GA), auxins and brassinosteroids (BR) regulate expansion along longitudinal axes and greatly influence plant structure and organ size.

Ethylene, the gaseous hormone and cytokinins act primarily to increase cell expansion along transverse axes and greatly reduce the stature of dark–grown seedlings. Abscissic acid (ABA) has been shown to antagonize growth promotion by both GA and BR. In addition Jasmonic acid (JA), Salicylic acid (SA), Nitric oxide (NO), Polyamines (Pas) and plant sterols are also known to play essential role in modulation of growth and development in plants.

During the past five years, it has become apparent that there are other novel signaling molecules, such as alkamides, glutamate and N acylethanolamides that might play important roles in the regulation of morphogenetic and adaptive processes. These might be involved diverse processes, including seed germination, pathogenesis, modulation of plant architecture and response to abiotic factors.

Plant hormones are affect diverse developmental processes. Alteration in hormone responses have been responsible for several important agricultural advances including the breeding of semi dwarf varieties and increased grain production (Green Revolution in cereals). Unlike animal hormones, which are produced in specific organs, plant hormones are typically produced throughout the plant. Virtually every aspect of plant development from embryogenesis to programmed cell and senescence is under hormonal control. In general, this developmental control is exerted by controlling, cell cycle, division, expansion, differentiation and cell dealt.

Diverse developmental processes can be controlled, including formation of the apical basal and radial pattern, seed germination, and seed dormancy, determination of plant architecture, flowering, fruit ripening and shedding.

Recent work by various laboratories have revisited the question of hormone specificity and uncovered extensive crosstalk and signaling integration among growth regulating hormones. A very high priority has been given to identification and characterization of the receptors that perceive the hormones. During 2005–2006, the receptors for the plant growth hormones, abscissic acid, auxin and gibberellins have been identified. These join the receptors that have previously been identified for brassionosteroids, cytokinins and ethylene.

plant hormones examples

Here is the list of some important examples of plant hormones. Which are as follow;

Auxin
Gibrellin
Cytokinins
Brassinosteroids
Ethylene
Abscisic Acid

People also ask

Q-1: What are the plant hormones functions?

Ans- Gibrellin hormones is help in breaking the dormancy of seeds and buds; promote growth.

Q-2: Where are plant hormones produced?

Ans- The plant hormones are produced in the stem, buds, and root tips.

Q-3: What are plant hormones three plant hormones?

Ans- The plant hormones are produced in the stem, buds, and root tips.

The plants hormones are;

Auxins
Gibrellin
Cytokinins

Q-4: Can plant hormones affect humans?

Ans-

Q-5: Which plant hormone is gaseous in nature?

Ans- Ethylene is gaseous in nature.

Q-6: Which plant hormone is found in gaseous form?

Ans- Ethylene is found in gaseous form.

Q-7: Types of plant hormones ?

Ans- There are some important plant hormones is as follows;

Auxin
Gibrellin
Cytokinins
Brassinosteroids
Ethylene
Abscisic Acid

Q-8: Plant hormones examples ?

Ans- Here is the list of some important examples of plant hormones. Which are as follow;

Auxin
Gibrellin
Cytokinins
Brassinosteroids
Ethylene
Abscisic Acid

Q-9: Plant hormones definition?

Ans- The plant hormones are produced in the stem, buds, and root tips.

Fruit ripening | fruit ripening hormone

2020-10-01T23:08:00.000+05:30

Fruit ripening|Fruit ripening hormone

Reproduction in flowering plants begins with the formation of the flower and ends with the formation fruit and seeds. Fruit development and seed set in flowering plants normally occur in coordinated manner following pollination of the stigma and subsequent double fertilization in the ovule, a female gamete forming structure, located with the carpel. When the egg and central cell of the female gametophyte are not fused with sperm cells, they remain in quiescent state and eventually degrade as the flower undergoes senescence. This has led to the interpretation that signaling processes are required to activate development of the fertilization products leading to the initiation of seed and fruit development.

Fruit development can be uncoupled from fertilization in plants that undergo the genetically controlled process of parthenocarpy and apomixes. Apomictic species can produce both fruit and viable seed in absence of fertilization.

Parthenocarpy has a genetic basis and has been exploited by farmers and plant breeders for the production of seedless fruits.
Most fruits develop from a gynoecium’s that contains one or more carpels. In pseudocarpic fruit, organs other than the gynoecium (e.g. receptacl bract, the floral tube, or the enlarged axis of the inflorescence) participate in the formation of fruit.

When an ovary develops into a fruit, the ovary wall becomes the pericarp. Fruit, protects seed development and server the vehicle for seed dispersal. Fruits also provide human with a source of nutrition, culinary diversity, and often great pleasure. Fruits from domesticated species often have been tremendously enlarged over that normally found in the progenitor wild species.

Initially, fruit enlarge through cell division and than by increasing volume. The embryo matures and the seed accumulates storage products, acquires desiccation tolerance, and less water. The fruit then ripens Ripening is accompanied by changes in aroma, color, flavor, nutritional contents, and susceptibility to opportunistic pathogens. Ripening can be generally defined as the summation of changes in tissue metabolism rendering the fruit organ attractive for consumption by organisms that assist in seed release and dispersal. The ripening renders, the fruit attractive (appealing) to organisms receiving sustenance in exchange for assisting in seed dispersal.

Ripening physiology has been classically defined as, either ‘climacteric’ or ‘non climacteric’. Climacteric fruits show sudden increase in respiration at the onset of ripening, usually in concert with increased production of ethylene. Ethylene is typically necessary for climacteric ripening. Non climacteric fruits do not increase respiration at ripening and often have no requirement for ethylene to complete maturation. Fruit growth, in most species, can be represented by sigmoidal curve. Physiologically and biochemically, fruit development can be divided into four phases, which although occur in continuity, are separated on the basis of the major activities. Phase I includes ovary development in the flower, and (following anthesis) a decision to abort or proceed with further development. Phase II involves a period of rapid cell divisions. Phase III is the period of most rapid growth, when cell divisions (more or less) ceases and growth is almost exclusively by cell enlargement.

During this phase, food reserves are accumulated and most fruits attain their final shape and size before the onset of ripening Phase IV. In some plant species another burst of growth occurs during the ripening period (and hence fruit of such types exhibit double sigmoid growth curve). In some fruits, such as avocado, cell divisions continue well into Phase III. There is much variation among flowering plants in the manner in which fruit arise. Fruit may arise from single or multiple fused ovaries of a single flower (simple fruits), from several single ovaries of a single flower (aggregate fruits), or from ovaries of several flowers in inflorescence multiple fruits.

Mature fruits can be generally characterized as either fleshy or dry. Fleshy fruits typically undergo ripening as defined above and dry fruits (cereals and legumes) mature in a process more akin to senescence and disperse their seeds via abscission like programs, including dehiscence or shattering.

Fruit ripening is a unique aspect of plant development with direct implication for large components of food supply and related areas of human health and nutrition. The ripening of fruit organs represent the terminal stage of development in which the matured seeds are released. Although the specific biochemical and physiological programs resulting in ripening phenomena vary among species, typical changes include (a) alteration in chlorophyll and carotenoid contents and accumulation of flavonoids resulting in modification of color, (b) alteration of cell turgor and cell wall structure and/or metabolism and change in texture, (c) modification of starch sugars, acids, and volatile profiles that affect nutritional quality, flavor, aroma and taste. From a practical viewpoint, a number of ripening characteristics result in negative quality attributes including decrease self–life and high input harvest, shipping/transport and storage practices. The ripening associated changes in firmness and overall decrease in resistance to microbial infection brought about by the ripening process and associated tissue deterioration are particularly important. Ripening has an impact on fiber content and composition, lipid metabolism, and levels of vitamins and various antioxidants. It is important to understand the process of fruit ripening as this will increase the ability to understand and manipulate, through breeding or biotechnology, key control points in the global control of ripening or specific stages/regulatory points of specific ripening process.

Climacteric fruit typically increase biosynthesis of the gaseous hormone ethylene, and display a burst respiration at the onset of ripening. Fruit such as apple, banana, pears and tomato exhibit climacteric fruit ripening. Interestingly climacteric fruit span a wide range of angiosperms both dicots and monocot. Non-climacteric fruit, including strawberries, grapes and citrus fruit do not require climacteric respiration or increased ethylene for maturation.

Surprisingly members of same (e.g. melon) or closely related (e.g. melon and water melon) species are reported to include both climacteric and non-climacteric types. Genetic and molecular distinction between climacteric and non-climacteric fruit ripening are poorly understood.

Nevertheless, it seems likely that non climacteric phenotypes may represent mutations in ethylene synthesis or signaling as opposed to more complex distinction.

Several mutants (spontaneous and induced) that affect fruit development and ripening have been identified and characterized particularly in tomato climacteric fruit).

Ripening in Climacteric fruits

Apple, Avocado, Banana, Cantalope, Mango, Olive, Papaya, Passion fruit, Peach, Pear, Plum and tomato are common climacteric fruits. These are also import commercial crops. In these fruits ethylene acts as an inducer of many genes associated with color change, changes in carbohydrate reserves, and softening of pulp. Ripening of climacteric fruit is induced by ethylene. It seems justified to assume that other factors that operate prior to induction of ethylene biosynthesis also control early developmental stages of ripening fruit.

Transgenic tomatoes, where, ethylene production is drastically curtailed by inserting the coding sequence of the ACC Synthase or the ACC oxidase gene in an antisense orientation, under control of strong promoter CaMV S 35,show no climacteric and do not ripen.

Ethylene production in plants results from methionine metabolism. The rate–limiting steps in fruit ethylene synthesis include the S–adenosylmethionine (SAM) to 1 aminocyclopropane–1–carboxylic acid (ACC) via ACC synthase (ACS) and the subsequent metabolism of ACC to ethylene by ACC oxidase (ACO). Both the ACC synthase and the ACC oxidase are encoded by multigene families. Anti-sense repression of ACS and ACO genes has clarified the role of these genes in regulating climacteric ethylene synthesis. It is also well known, however, that ethylene alone is not sufficient for ripening and that a developmental “competence” to responds to ethylene must be achieved.

This is obvious from the fact that immature fruit typically do not ripen in response to exogenous ethylene. Climacteric fruit ripening is regulated by developmental factors that must properly coordinate with ethylene synthesis. These include colorless non-ripening (Chr) ripening inhibitor (rin) and non–ripening (nor).

Valuable information has been generated through studies on developmental mutations that affect all aspects of the fruit ripening processes at least in tomato. These include colorless non–ripening (Chr), ripening inhibitor (rin),non–ripening (nor).

Figure 24-Fruit ripening mutants of Tomato (from left to right ,ripe fruit of wild type ,ripening inhibitor(rin), non-ripening(nor), Never-ripe(Nr)and Green-ripe(Gr).

In these mutants fruit ripening is severely impaired. These do not undergo an increase in ripening–related ethylene production and show inhibition of ripening related gene expression. In these mutants, however expression of ripening–related genes is partially restored but not ripening by application of ethylene. Thus these mutants remain ethylene responsive.

Although a complete molecular biological and signal transduction pathway remain to be identified/defined. An important first step towards this goal came from the discovery that the rik locus encodes a MADS–box transcription factor necessary for regulating ripening. In other two mutants of tomato Green–ripe (Gr), and Never–ripe (Nr) studies have indicated that their reduced ripening results from decreased ethylene sensitivity.

Light has been shown to affect carotenoid accumulation in plants. It has been shown that phytochrome mediated light signal transduction is required for normal ripe fruit pigmentation but it not affect other ripening attributes.
The change from a green fruit to ripe apple, banana and tomato involved a transition of chloroplasts to chromoplasts. Chlorophyll pigments and thylakoid membranes are broken down. A progressive accumulation of new carotenoid pigments occur in the plastids. The new carotenoids in tomato include β–carotene and lycopene.

These provide the orange and red color for the ripe fruit respectively. Lycopene synthesis is induced by ethylene, and is shutt off by inhibitors of ethylene synthesis or perception. Fruit of Banana, Kiwi fruit and mango synthesize and accumulate starch during development. During ripening these fruits hydrolyze starch and convert it into sugars. Fruits of Melon like systems continuously import sugars from other parts of the plant. During ripening, the fruits show an increase in the concentrations of sugars.

Moreover, sucrose is hydrolyzed to hexoses. Ethylene–induced upregulation of mRNAs of enzymes involved in starch/sugar metabolism (such as sucrose phosphate synthase and acid invertase) occur during ripening in several fruits. These events change sweetness of fruit.
Production of organic acids (principally citric acid but also malic acid) and volatiles increase while fruits ripen.

These combine to produce the unique flavor and aroma. Production of phenolics, provide astringency to unripe fruits. These have profound influence on the flavor and color of mature fruits.

Fruit texture changes drastically during ripening. The cell walls are degraded by increased activities of various hydrolyzing enzymes. Distruption of the cellulose hemicellulose and petin networks is done by the increased activities of enzymes. The wall–loosening enzymes, such as endo–1, 4 β–glucanases (E Gases) and xyloglucan endotransglycosylases (XETs), are activated. Genes encoding expansive and XETs, and E Gases expressed during fruit ripening are induced by ethylene and down regulated by auxin. Activities of enzymes; Pectin methylesterase (PME) ad polygalacturonase (PG) are enhanced during ripening fruits.

These affect large changes in pectin structure. The production of PG is under developmental control. The engyme is absent in green fruits and is synthesized de novo during ripening. It production is controlled by ethylene. The activities of stress/pathogen inducible enzymes, superoxide dismutase (SOD) and catalase occur in ripening fruit. Both of these are known for antioxidant activities.

Ripening and non-climacteric fruits:

Strawberry has been studied among the non-climacteric fruits. Majority of the changes that occur during ripening of non climacteric fruits are similar to the changes that are seen in ripening of climacteric fruits.

Ripening of non-climacteric fruits (at least in strawberry) is not affected by exogenous ethylene and inhibitors of ethylene biosynthesis and ethylene response/action. Auxins retard/inhibit ripening related changes in strawberry.

Grape berry and citrus fruits are two other non-climacteric fruits. Treatment with auxin retards ripening of these fruits. Citrus fruit is unusual; it is non climacteric fruit, but carotenoid synthesis in the orange peel is regulated by ethylene.
Abscission of mature/ripe fruit, similar to leaves and flower pedicels is regulated by ethylene. Abscission is inhibited by auxins, cytokinins and cytokins.

Vernalization in plants | Meaning, Definition

2020-09-30T15:02:00.001+05:30

Vernalization in plants

As the plants are sessile organisms, they have to readily alter their development and growth responses to survive an ever changing environment. In all facets of development, from germination to flowering, plants use correct amalgamation of multiple external signals including light and temperature. Temperature as an environmental factor profoundly influences developmental programs of plants.

Temperature plays a major role in controlling the degree of seed dormancy/seed germination and vegetative growth. In some plant species, long cool winter periods, are required to enable flowering. This inductive process, called vernalization, is a strategy that ensures flowering only occurs in the more desirable spring or summer climate.

vernalization definition | vernalization meaning

This vernalization is the process by which flowering is induced/promoted by a cold treatment given to a hydrated seed or to growing plant. Day seed do not respond to the cold treatment. Over the 20th century, vernalization has been studied extensively at the physiological level. Gassner (1918) reported that a wide range of plant species require cold treatment/exposure to flower.

The infamous Russian geneticist Trofim Lysenko, who studied the effect of cold on flowering, coined the term jarovization to describe what we now vernalization. Spring cereals are called jarovoe in Russian (derived from Jar, the god of spring) and cold exposure causes a winter cereal to behave like a jarovoe (i.e. flower rapidly). Jarovization was translated from Russian into vernalization; vernal is derived from latin word for spring, vernum.

Figure 22-Vernalization induces flowering in the winter-annual types of Arabidopsis thaliana. The plant on the left is a winter annual type that has not been exposed to cold. The plant on the right is a genetically identical winter- annual type that was exposed to 40 days of temperature slightly above freezing (40C) as a seedling .it flowered 3 weeks after the end of the cold treatment with about 9 leaves on the primary stem.

Vernalization should be followed by inductive photoperiod to flower. If vernalized plants are grown non–inductive photoperiods, they continue to grow vegetative. However, if such plants are later shifted to inductive photoperiods, they still flower. This shows that the vernalized plant remember their prior vernalization ; that is, they had acquired competence to flower but did not actually do so until the photoperiod requirement was met. Thus a cellular memory is established by exposure to cold treatment that is stable through mitosis, but, importantly not through meiosis. The length of this memory winter varies among plant species.

Two types of experiments demonstrate that this acquisition or acceleration of flowering after chilling treatment occurs at the shoot apex. Another is to graft short tips: In most species, if vernalized shoot tip as grafted to non–vernalized stock, it will flower, but a non vernalized shoot tip grafted to vernalized stock will not flower.

The effective temperature range for vernalization is just below freezing to about 10°C, with broad optimum usually between about 1 and 7°C. The effect of cold increases with duration (4 to 12 weeks) of the cold treatment until the response is saturated. Vernalization is a quantitative response with increasing periods of low temperature causing progressively the earlier flowering until a saturation point is reached.

Vernalization can be lost as a result of exposure to devernalizing, conditions, such as high temperature, but the longer the exposure to low temperature, the more permanent the vernalization effect.

Vernalization is an epigenetic switch

Vernalization is effective, if active metabolism occurs during the cold treatment. Sources of energy and oxygen are required, and temperature below freezing at which metabolic activity is suppressed is not effective for vernalization. It has been suggested that the vernalization induced, mitolically stable acquisition of the competence to flower, be referred as an epigenetic switch because it is a change that can be propagated through cell division in the absence of the inducing signal. However, there may be disagreement over the use of the term epigenetics. Some might argue that the term epigenetics should be used only for changes that persist from one generation to the next. This is course does not happen in the case of vernalization.

Nevertheless, many studies have shown that the vernalization state can be stable; i.e. after exposure to cold has ended, competence to flower, in certain species, can persist for many months and throughout many cell divisions in the shoot apical meristem.

Genetics and Molecular Mechanisms of Vernalization:

In naturally occurring Arabidopsis accessions, FRIGIDA (FRI) and FLOWERING LOCUS C (FLC) determine the requirements for vernalization. FRI encodes a novel protein that increases the mRNA level of the MADS domain gene FLC. FLC acts as a strong floral repressor by negatively regulating the expression of genes that promote the floral transition including SOC 1/AGL 20 and FT. Vernalization promotes flowering by reducing FLC mRNA levels by antagonizing FRI function. The extent of this reduction is proportional to the duration of vernalization and is closely correlated with flowering time.

FLC expression is also down regulated by the action of genes of autonomous floral promotion pathway i.e. FCA, LUMINIDEPENDENS (LD), FVE and EPA. Mutations in these genes cause increased FLC levels and a late–flowering phenotype that can be reversed by vernalization. Several VERNALIZATION (VRN) genes have been identified which mediate the vernalization responses in Arabidopsis. VERNALIZATION 1 (VRN 1) is plant–specific DNA binding protein. VRN 2 is a relative of polycomb group protein. VERNALIZATION INSENSITIVE 3 (VIN 3) contains PHD domain. In yeast and animals, proteins related to VIN 3 and VRN 2 are involved in chromatin remodeling complexes. Such complexes often cause modification of histone(s). The spectrum of histone modifications and their effect on gene expression are referred as the histone code.

Vernalization brings changes in FLC chromatin. After vernalization and during vernalization, the levels of certain modifications are associated with active genes are reduced, such as acetylation of histone 3 (H 3) at Lys 9 and 14. By contrast, the levels of two other modifications, methylation of H3K9 and H3K27 are increased by vernalization. Elevated H3K9 and H3K27 methylation is typically associated with the formation of stable heterochromatin. Thus, the vernalizaion–mediated formation of heterochromatin at FLC appears to account, at least in part, for the epidenetic nature of the vernalization state. Histone deacetylation is one modification of FLC chromatin that occurs during vernalization.

phototropism in plants | phototropism examples

2020-09-29T10:06:00.000+05:30

Phototropism in plants

Phototropism, or the directional curvature of organs in response to lateral differences in light intensity and/or quality, is one of the most rapid and visually obvious responses of plants changes in their light environment. A number of plant organs respond to phototropic stimuli. Stems, in particular exhibit positive phototropism, while roots exhibit negative phototropism.

Phototropic responses are distinguished from other types of light–modulated directional growth responses, such as nastic and circadian regulated leaf movements by two criteria : (1) the direction of phototropic curvatures is determined by the direction of the light stimulus while direction of nastic/circadian regulated movements, are not, and (ii) many leaf movement responses occur as a result of reversible swelling/shrinking of specialized motor, or pulvinar, cells, whereas all stem and root phototropic responses are driven by changes in cell elongation rates across the binding organ. The differential growth rates, driving the development of phototropic curvatures to be established as a result of differential responsiveness to the plant hormone “auxin” which is Greek for “to increase”– an appropriate name given its properties to promote cell elongation.

Cholodny (1927) and went and Thimann (1939), independently, proposed that it was due to distribution of a growth promoting substance from one side of a plant to the other that lead to the photoperiodic response. Perception of photons of light energy leads to a differential growth response that is potentially based on hormone gradient.

Phototropins, a class of chromoproteins sense blue–light mediate blue–light–induced phototropic responses. While other families of photoreceptors such as the phytochromes and cryptochromes play varying roles in phototropic responses. PHOT 1 AND PHOT 2 are two phototropins in Arabidopsis. PHOT 1 was first of the phototropins. Its mutant (Phot 1) showed impaired phototropic response under low fluence blue light. Under high fluence blue light, however, Phot 1 mutant exhibited a normal jphototropic response. PHOT 2, the second phototropin was identified through sequence homology to PHOT 1. Phot 2 single mutants retained an essentially wildtype response under all fluence rates tested. Double mutant Photo 1 Phot 2 lack phototropic responses in both low and high fluence rate blue light. Thus Phot 1 and Phot 2 function redundantly as high light receiptors, while Phot 1 acts as the low–light photoreceptor. PHOT 1 is 124 KD and PHOT 2 is 110 KD. Phototropin 1 has two LOV (light, oxygen and voltage) domains, LOV 1 and LOV 2, in the N–terminal region and domain homologous to serine threonine kinase towards the C–terminus.

The LOV domain absorb blue light through an associated flavin mononucleotide chromophore while the kinase domain thought to be associated with signal transduction. Phot 1 and Phot 2 are phototropic receptors but these represent only two of molecularly known receptors in Arabidopsis.

It has been suggested that at least in elioted seedlings cryptochromes and phytochromes do not function as primary phototropic receptors. Phytochrome family has been proposed to act together with blue–light receptors to mediate phototropic responses in deetiolated (light–grown) seedlings of number of plant species.

Recent finding that an auxin–responsive transcription factor is necessary for proper phototropic curvature (response) gives credence to the long held notion that the phototropic response is based on an auxin gradient. This further suggests that changes in gene expression are necessary component of the phototropic response system.

Phototropism Examples

Thigmotropism

Thigmotropism is the response of a plant organ to a mechanical stimulation. One can imagine that the gravitropic and thigmotropic response of root might be intimately related. In fact, a recent study suggests that proper root tip growth requires the integration of both a gravity response and a touch response. A group of five genes termed the TOUCH (TCH) family, are responsible for mechanosensory responses in Arabidopsis. TCH 1 encodes a calmodulin (CaM) while TCH 2 and TCH 3 encode calmodulin–like genes.

Hydrotropism

Hydrotropism can be defined as growth or movement in a sessile organism towards or away from water.

Preference of roots for soil with a higher water potential is the best example of hydrotropism. Plant roots penetrate the soil in search of highest potential. However, there is little knowledge about the mechanism through which this actually happens. We know that gravity is the driving force behind a root’s downward growth. This growth is modulated by mechanostimulation of soil particles. The search for highest water potential is likely to play some role in the integrated growth response. The difficulty in studying hydrotropic growth comes in separation of this response from other tropic responses, gravitropism chiefly among them and drought responses that can occur if plants are water stressed. This is further complicated due to the fact that the root cap is proposed as signal integration center for both the gravitropic and hydrotropic responses. Most studies of hydrotropism have been done using on either pea mutants, ABA, auxin or agravitropic mutants of Arabidopsis or maize roots. Calcium is important for a hydrotropic response as is auxin and potentially other plant hormone responses. Recently two mutants have been identified in Arabidopsis which do not show a hydrotropic response.

People Also Ask

Q-1 What is Phototropism in plants?

Ans- Phototropism, or the directional curvature of organs in response to lateral differences in light intensity and/or quality, is one of the most rapid and visually obvious responses of plants changes in their light environment. A number of plant organs respond to phototropic stimuli.

Q-2. What is an example of Phototropism?

Ans- Positive phototropism is growth toward a light source, and negative phototropism is growth away from a light source. ...the best example of positive phototropism is Sunflowers, because they not only move their stems curve torards the light but also their flower turn and face the sunlight as well.

Q-3 Where does negetive phototropism occur in plants ?

Ans- When the level of auxin or auxin signaling is reduced to its minimal level.

paddy blast | paddy blast disease

2020-09-12T22:22:00.000+05:30

paddy blast | paddy blast disease

Class	Deuteromycetes
Sub-Class	Hyphomycetede
Order	Moniliales
Family	Monoliolose
Pathogen	Pyricularia oriza

Symptoms of Paddy blast

Symptoms on leaf appear on small spindal shape spot with brown margine. The center of the spot is whitish grow. Such spores like appear on the collum, collum nodes and glumes.

The neck become shrivelled and covered with gray fluphy Mycelium and bends down due to Waite of the year.

The infected grain are also shrivelled.

Source: easybiologyclass

Causal Organism

Pyricularia oriza
Mycelium consists of septate gray to olivesious hypha mostely located in leisons.
Conidiospores are haline monoseptate dentipelate and produced through stomata or by repturing the cuticle. Conidia are produce in succession one at a time at the tips of conidiospores. Conidia are biseptate, haline olivasious pyriform to obclavate with rounded base and narrow towards the tip.

Disease Cycle

Sori of primary inoculum is not definitely known.

The initiation occur through the conidia Mycelium can survive in infected Structure for 1 or 2 year.

Under dry condition bud during humid condition. It is generally destroy due to microbial activity.

The fungus also infected in the seeds during the stage but the seed borne inoculum do not succeed because high soil temperature in May and June.

Controls

Sanitation
Seed treatment
The folior spray copper fungicide are effecting in controlling the blast in some variety.
Use of resistance variety CO-4, CO-25, CO-26 are the variety found to be highly resistant variety to blast disease.

This article share by Alpine Study

Ovule Meaning | Ovule Diagram

2020-09-09T11:02:00.001+05:30

Ovule Meaning

The ovule is a component of the makeup of the feminine sex organ in seed plants. It’s the place where female reproductive cells are made and contained, and it's what eventually develops into a seed after fertilization, just for the seed to then ripen and produce a complete adult plant. Ovules are contained in ovaries at rock bottom of a vase-like structure, the carpel, which features a neck called a method and a gap at the highest , called a stigma. Ovule starts swell After fertilization and it's wall also starts to toughen in preparation to become a seed, while the ovary starts to grow around it and becomes the fruit. Keep in mind that some plants, just like the avocado, have one ovule in their ovary, while others, just like the kiwifruit, have many, which become many seeds within the fruit. Another way that plants differ with regards to their ovules is that the place where the ovules are found. Specifically, the ovules are found inside of the ovary within the carpel.

Parts of Ovules

The ovule is made of Nucellus, the part of the ovules that form the outermost layer, and the female gametoohyte ( called embryosac in flowering plants), which are found at the distinct center.

The Nucellus

The nucellus is that the largest a part of the ovule. It houses the embryo sac also as nutritive tissue and truly remains present in some flowering plants after fertilization as a source of nutrients for the embyo.

The Integuments

The integument is that the tough outer protective layer of the ovule. In the diagrams below we will see that gymnosperms, like pine trees and spruce trees, usually have one integument in an ovule, so we call them unitegmic. On the opposite hand, angiosperms, like maples and daisies, typically have two integuments, and that we call them bitegmic. The integument encloses the nucellus apart from alittle gap, which is named the micropyle.

Ovule diagram

The Female Gametophyte

This is the part of the ovules that contains the gamete-producing sex organs, which are critical for sexual reproduction. Single set of unpaired chromosomes, contains by the female gametoohyte, this is haploid in nature. It is commonly called megagametoohyte or embryo sac.

Types of Ovules

Ovules are separated into six categories supported their shapes:

Orthotropous (Atropous)

This is where the body of those ovules is straight in order that the chalaza, where the nucellus and integuments merge, the funicle, which attaches the ovule to the placenta, and the micropyle are all aligned.

Anatropous

In this case, the ovules become completely inverted during development in order that the micropyle lies on the brink of the hilum. The hilum may be a scar that marks the purpose where the seed was attached to the fruit wall by the funicle.

Hemi Anatropous

The body of those ovules becomes at a right angle in reference to the funicle, so it's just like the ovule is lying on its side.

Campylotropous

The body of this sort is bent and therefore the alignment between the chalaza and micropyle is lost. The embryo sac is only slightly curved.

Amphitropous

The body of the ovule is extremely much curved that the embryo sac and therefore the ovule itself take the form of a horseshoe.

Circinotropous

The funicle during this case is particularly long that it creates an almost full revolve around the ovule whose micropyle is ultimately pointing upwards.

Ovules function

The ovule plays a vital role in sexual reproduction. Once a pollen grain lands on the stigma of a flower of its same species, it sends out a plant part down through the design . This tube then enters in the ovary and reaches the ovule of the plant. Once that happens , fertilization can arise because the nucleus of the pollen grain is shipped down the tube to merge with the nucleus within the embryo sac.

Related Terms

Anther – Anther is the part of the stamen that contains male Gametophyte or pollen grains.

Asexual Reproduction – In asexual reproduction the genetically identical offspring are produced without the formation of gametes from a single parent.

Diploid – A organism or nuceleus, cell that contains two set of chromosomes, one from male parent and another from female parent.

Pollination– The transfer of pollen to the female reproductive organs of the same plant or a different plant of the same species.

History of Taxonomy | Taxonomy hierarchy | History of plant Taxonomy

2020-08-21T14:45:00.003+05:30

Taxonomy hierarchy

The one of the earliest disciplines of Botany is Plant Taxonomy. It was started as ―Folk Taxonomy in early 15th century but it has grown and gone very long way in the last 500 years. Now the scope and concept of plant taxonomy changed a lot.Rich flora, tropical countries are under threat. So far 4,000,000 plant species are identified of which 2, 86,000 are of angiosperms. Among the identified plants about seventy percent belong to tropical regions.

People are running for the applied sciences, In the modern times as genetics, cytology, experimental biology, ecology, molecular biology etc. but a few people are thinking of the fundamental or basic branches of botany like Morphology and Taxonomy. It has become an old fashion. No applied branch can be approached without the proper identification of the plant material on which he/she is working and for this taxonomists are very much needed.
With the increased need for conservation of biological resources, the need for biodiversity assessment during the last few years has increased. However, the trend has reversed and taxonomic studies are being encouraged throughout the world.

Simpson (1961) suggested that systematics included identification, taxonomy, classification and nomenclature and used as the scientific study of the kinds and diversity of organism and of any and all relationship between them. de Candolle (1813) first coined the term taxonomy.
The basic unit of classification is species which are grouped into genus and further grouped into family suborder, order, subclass, classes and divisions.

The beginning of the classification of organism took place at remote times by the non civilized people for their usage and in their own language, with the development of language the distinction between carnivores, herbivores, poisonous plants, edible plants etc. became clear. They feel the necessity of different plants and animals for their use. They selected certain plants and animals for festivals.

In this way, the classification in crude sense got the foothold in the society. Folk systematics is gaining popularity among the pre civilized men. They recognized groups of plants on the basis of gross morphology. This is the beginning of the artificial system of classification. Their ways of classification are rooted in their practical considerations.

The history of classification starts from the time of the earliest Indian Philosophers like Charak, Sushruta, early Greek philosophers like Aristotle, Plato, Pliny and others also tried to classify plants from their own viewpoint which invariably were more philosophical in nature than scientific. The various classifications of plants proposed so far, belong to either of the three categories:

(a) Artificial: System classifies plants with the help of one or few characters, primarily with a intention of easy identification of the organism e.g. Banhin, Tournefort, John Ray, Carl Linnaeus.
(b) Natural: System is mainly based on from relationship realizing all informations available at that time. e.g., de Candolle, Robert Brown, de Lamarck, Bentham and Hooker‘s classification.
(c) Phylogenetic: System tries to classify plants based on their genetic relationships and according to their evolutionary sequences. e.g., Eichler, Hutchinsm, Bessey. C. Jeffrey (1982) presented that the system of classification can be divided into four main types:
(a) Artificial: Habit based classification made upto 1830.
(b) Pre evolutionary Natural Systems: Overall similarly between plants were much more natural e.g., Bentham & Hooker, A. P. de Candolle, de Jussieu.
(c) Phylogenetic Systems: Natural grouping as a result of decent or common character are related to each other through a common ancestry, e.g., Eichler, Engler.
(d) Phenetic System: Maximal generalizations of the totality of the features of all phenotypes e.g. Hutchinson.

HISTORY OF TAXONOMY | HISTORY OF PLANT TAXONOMY

The history of plant taxonomy or The history of taxonomy begins with compartmentalisation, of useful plants of folk taxonomy. People differentiated them as economic plants. This paved the way for herbal taxonomy. The history can be studied in different phases as follows:

I. Initial Stage

Theophrastus (370-285 BC) a Greek Naturalist also known as Father of Botany published―Enquiry into Plants‖. He proposed Crataegus, Daucus (daukan), Asparagus (aspargos) and Narcissus etc. in his work. Theophrastus classified plants on the basis of habit as herbs, undershrubs, shrubs, trees. He gives the name and description to 500 plants in Historia Plantarum oldest botanical work in existence. He pointed out the differences between dicots and monocots.

Pliny (23-29) AD wrote multivoluminous Natural History of which 37 volumes are present.

Pedanion Dioscorides (62 - 128 AD), a physician of Asia minor described 600 medicinal plants. His book was named Materia Medica in Greek.

Andrea Caesalpino (1519 - 1603 AD) a Italian physician wrote De Plantis (1583), 1500 plants were described, Woody / herbaceous.

Gaspard Bauhin (1560 - 1624 AD) Collected the plants from Italy, France, Switzerland, Books are Prodromus Theati Botanici (1620), Penax Theati Botanici (1623). He first attempted to use binomial system of nomenclature.

John Ray (1628 - 1705 AD). British Botanist published 3 volumes Historia Plantarum (1686 - 1704). He is the first who divided the herbs / trees and divided monocotyledons and dicotyledous on the basis of one and two cotyledons.

J. P. de Tournefort (1656 - 1708) described trees and herbs and considered corolla.

The first herbarium was established in 1553 in Padua (ITALY)

In the middle of 17th century, herbaria were established in different parts of the world.

Carolus Linnaeus (1707 - 1778), a Swedish Naturalist also known as father of modern botany / taxonomy. He published Genera Plantarum (1737), Classes Plantarum (1738), Philosophia Botanica (1751), Species Plantarum (1753). After giving breif description of 7300 species arranged them on sexual system. This system was an artificial system based on few characters of plants. He introduced Binomial system eg., Rhododendron arboreum. 24 classes of Linnaeus are (1) Monandria (one Stamen) (2) Diandria (2 stamen) ........ (24) Cryptogamia (No flower).

In initial stage taxonomy was merely started for exploration and naming of species.

II. Natural System Stage

Antoine L de Jussieu (1686 - 1758) published Genera Plantarum and classified plants into 15 classes.

Augustin Pyrame de Candolle (1778 - 1841), a French botanist published Theorie elementaire de la botanique in 1813 and developed morphological approach to classification. He classified plants as Vasculares and Cellulares, Monumental works-Prodromus Systematis Naturalis Regni Vegetabilis. A. P. de Candolle could not complete his work and later his son Alphonse de Candolle completed the work.

Charles Darwin (1859) published Origin of Species, where he suggested the principle of natural selection and evolutions of species.

Bentham and Hooker (1800 - 1884) published Genera Plantarum (1862 - 1883) gave practical use of classification ―ever since been as inspiration to generations of the Kew Botanists‖.

III.Phylogenetic Stage

Phylogenetic classification was based on the ideas of evolution. Phylogenetic classification started with Eichler (1837 1887) and Endlichler (1804-1849).
Engler and Prantl. (1887-1915) suggested semi-phylogenetic system of classification.

Die Natiirlichen Pflanzen Familien (1887 - 1899) and Syllabus der Pflanzen Familien (1964). He placed monocots before dicots and orchids were considered more evolved than grasses.

Class 1 : Monocotyledons - 11 orders

Class 2 : Dicotyledons

Sub class - 1. Archichlamydeae - 29 orders.

Sub class 2. Metachlamydeae (Sympetalae) - 9 orders

A. B. Rendle (1865 - 1938) Classification of flowering plants. He treated monocots as primitive to dicots and amentiferae and apetalous as primitive dicots.

The first purely phylogenetic system based on Dictas of Phylogeny was given by Charles Edwin Bessey (1845-1915) which was improved by Hans Hallier (1868-1938)

John Hutchinson (1884 - 1972)) Britishers, put forth his 24 principles of phylogeny and based on that suggested phylogenetic classification of value, in Families of Flowering Plants (1959). His classification was based as Bentham and Hooker and Bessey. First volume deals with Dicots (1928), second with Monocots (1934) and published British Flowering Plants (1940).

IV.Recent Stage

The system was improved by contemporary Botanists like Takhtajan in Flowering Plants: Origin and Dispersal (1969); Cronquist in “Evolution and Classification of Flowering Plants” (1981) Stebbins in Flowering Plant Evolution above the Species Level (1974) and Robert Thorne in ―A Phylogenetic Classification of Angiospermae” (1976) etc.

The Classifications were based on distribution, Ecology, Anatomy, Palynology Cytology and Biochemistry apart from Morphology.

Techniques of herbarium preparation and presentation were developed and established.

V. Biosystematic Phase

The last fifty years have seen a qualitative improvement in the area of taxonomic concept and application by advancement of Biosystematics.

The ―New systematics‖ is aimed at achieving the goal of ―holotaxonomy‖.

Huxley (1940) proposed the term ―New systematics.‖

Camp and Gilly (1943) proposed the term ―Biosystematics‖ to new systematics.

The number, size and shape of chromosomes were considered by cytotaxonomists as very reliable parameters for cytotaxonomic classification.

The development of techniques like two dimensional paper chromatography, identification of chemical substances in plants as secondary metabolites led to the development of―Chemotaxonomy‖.

The new techniques can give details as amino acid sequencing and determining nucleotide sequences in DNA and RNA.

VI. Holotaxonomic Phase

Information is gathered, analysed, and a meaningful inference is drawn for understanding phylogeny.

Collection of data, analysis and synthesis are the jobs of an independent descipline of taxonomy, i.e., Numerical Taxonomy.

Numerical Taxonomy or quantitative taxonomy is based on numerical evaluation of the similarity between groups of organisms and the ordering of these groups into higher ranking taxa on the basis of these similarities.

Exploratory and Consolidation phase are considered as Alpha taxonomy while Biosystematic and Encyclopaedic phase are considered as Omega Taxonomy.

FUNDAMENTAL COMPONENTS OF TAXONOMY

Taxonomy is a fundamental science with the increase in knowledge of various components developed.

(i) Descriptive taxonomy or Alpha Taxonomy :

The description and designation of species is concerned with the aspect of taxonomy. Typically on the basis of morphological characters, it developed in 19th century. It started with work of Tournefort, de Jussieu and Linnaeus.

(ii) Macrotaxonomy or Beta Taxonomy :

Beta taxonomy or Macrotaxonomy is the arrangement of species in the hierarchical system of taxa or higher categories. It developed in 20th century.

(iii) Gamma Taxonomy:

Aspect of taxonomy concerned with intraspecific population and with phylogenetic trends are included in gamma taxonomy. An attempt is made to account for the origin and development of species. To determine the origin of a species, a taxonomist has to depend on paleobotany which includes all taxa of extinct plant groups.

(iv) Omega taxonomy:

Omega Taxonomy is an ultimate perfect system. This is based on the all available characters.

AIMS OF TAXONOMY

There main aims of taxonomy, is Identification, nomenclature and classification. There are two main approaches:

(a) Empirical approach:

Empirical approach is based on observation of characters and practical aspects.

(b) Interpretive approach:

The classification is based on interpretation and evolution of a taxon, e.g., phylogenetic system.
Modern taxonomy combines this both approaches with the following aims:

1. To provide a appropriate method of communication and identification.
2. To provide classification which is based on natural affinities of organisms as far as possible.
3. To provide an inventory of plant taxa by means of flora.

4. To detect evolution at work, discovering its process of interpreting into results.
5. To provide an integrating and unifying role in the training of biology students regarding the relationships between many biological fields and data gathering science.

Key Questions

What is the history of taxonomy?
Who invented the taxonomy?
Who is the father of taxonomy and why?
Taxonomy Classification?
Describe evolutionary history of taxonomy in breief?

Ranunculaceae | Ranunculaceae Family | Ranunculaceae family plants

2020-08-19T12:23:00.000+05:30

Ranunculaceae | Ranunculaceae Family | Ranunculaceae family plants

You must be knowing different types of classification for angiospermic plants in your previous units. The classification used in Indian subcontinent is that proposed by Bentham and Hooker. In Genera Plantarum, Bentham and Hooker discussed 163 families under dicotyledons. Economic importance of each family is also discussed in some detail.

The dicotyledons include all those angiosperms in which the embryo possess two cotyledons, leaves with reticulate venation and vascular bundles are open and arranged in one or more rings. These plants have secondary thickenings in the stems. Due to the presence of the cambium. These plants may be either herbaceous or woody, having pentamerous flowers. They posses persistent primary root that develop into tap root.

Ranunculaceae Family, Caryophyllaceae and Rutaceae belong to Polypetalae (Petals are free and flower with Calyx and Corolla) group. Of them Ranunculaceae family and Caryophyllacee belong to SeriesThalamiflorae (Polysepalous, petals hypogynous) while family Rutaceae belongs to Disciflorae (Thalamus expanded into a disc , ovary superior).

The members of the subclass Polypetalae contain flowers with free petals and their perianth is usually in two whorls i.e. calyx and corolla . Polypetalae divided into 3 series e.g, Thalamiflorae, Disciflorae and Calyciflorae. Series Thalamiflorae is characterized by

(i) Usually distinct sepals free from ovary
(ii) presence of many stamens
(iii) Hypogynous flowers
(iv) superior ovary and
(v) Absence of disc

Thalamiflorae includes 6 cohorts (= orders) and 34 orders (= families) Series Disciflorae is characterized by
(i) distinct or united sepals free or adnate to ovary
(ii) stamens hypogynous,
(iii) usually definite flowers
(iv)superior ovary and
(v) presence of disc. Disciflorae includes 4 cohorts ( = orders) and 23 orders (= families) Series Calyciflorae is charactrised by
(i) Usually inferior ovary
(ii) Usually free sepals and flowers or United perigynous or epigynous. It includes 5 cohorts ( = orders) and 27 orders (= families)

RANUNCULACEAE FAMILY

Bentham & Hooker included family Ranunculaceae under Ranales, one of the 8 orders (families). It is commonly known as Buttercup family. This follows the work of the Angiosperm Phylogeny Group.

Armen Takhtajan 1997 includes the Ranunculaceae as the only family in the Ranunculales which he placed in a subclass, the Ranunculidae, instead of a superorder. In 1992,Thorn placed the Ranunculaceae in the Berberidales, an order within the Superorder Magnolianae. In 1981, Cronquiest included the Ranunculaceae along with seven other families in the Rancunculales which was included in the Magnoliidae, which he regarded as a subclass.

Diagnostic characteristics -

Herbaceous leaves palmately divided, flowers with many stamens, gynoecium of many simple pistils, fruit an aggregate of achenes or follicles.

Distribution pattern

It is a large family and includes 50 genera and 1900 species. It is mostly distributed in the temperate regions of the Northern Hemisphere. In India this family is represented by 20 genera and 165 species, mostly confined to the Himalayan region of Pakistan and India.

Systematics

General Characteristics

Habit:

Annual or perennial herbs, rarely shrubs or vines (Clematis). Some species are aquatic herbs (Rannunculas aquatilis). The perennial species usually develop rhizome and tuberous root (Aconitum and Ranunculus)

Roots:

Tap as well as adventitious root, Tuberous root (Aconitum)

Stem:

Herbaceous (Rannunculas), woody (Paeonia) or climbing (Clematis) stem, develops rhizome

Leaves:

Usually basal and cauline, Petiolate. Usually exstipulate but stipulate in Ranunculus Alternate rarely opposite (Clematis). Simple, pinnately compound (Clematis), decompound (Thalictrum) some aquatic species show heterotrophy, reticulate venation. The leaves are modified into tendrils in Clematis aphylla and photosynthesis is carried out by the stem.

Inflorescence:

Inflorescence is variable. sometimes raceme (Aconitum), Dichasial Cyme (Rannunculas sp.), axillary (Clematis), solitary and terminal (Nigella)

Flower:

Rarely bractate, Pedicillate ebracteate hermaphrodite, unisexual in Thalictrum actinomorphic (Rannunculas sp.) rarely zygomorphic (Delphium), hypogynous, complete, pentamerous, Regular.The floral parts are arranged spirally on the elongated receptacle. An involucres of leaves is present outside the calyx.

Calyx:

Sepals 5-8 which are distinct and usually deciduous, free, In Delphinium and Aconitum the sepals are petaloid and the posterior sepal is spurred. Aestivation is imbricate

Corolla:

5 or more petals or sometimes petals may be absent, polypetalous, variously colored, Sometimes, petals are changed into nectaries, In Delphinium the posterior pair of petals forms spur which projects into the spur of the sepal, another pair of the petal if present is very much reduced (Aconitum). In Clematis petals are altogether absent and sepals become petaloid.

Androecium:

Stamens are numerous, polyandrous. Stamens are Spirally arranged on the thalamus, In some genera (Nigella and Aquilegia) the stamens are arranged in definite rings, anthers adnate, dithecous, extrose, dehiscing longitudinally.

Gynoecium:

Numerous free carpels (Polycarpellary) arranged spirally on a distinct thalamus (one to three carpels in Delphinium), apocarpous rarely syncarpous (Nigella), ovary superior, one to several ovules in each ovary. Placentation basal or marginal.style and stigma one.

Fruits:

An etaerio of achenes or follicles, sometimes berry or capsule.

Seed:

Small, endospermic seed

Pollination:

Generally entomophilous

Floral formula

Important Genera

The familiar examples of the family are Delphinium (Larkspur) Thalictrum (Meadowrue) (Ranunculus (Butter-cup) Nigella (Kala-jeera), Anemone (Wind flower), Aconitum (Aconite)

Economic importance

1-Ornamental plants:

Most plants are cultivated for their beautiful flowers like Ranunculus (Buttercup), Thalictrum, Clematis etc.

2-Medicinal plants:

Some members are used as medicinal plants. Aconitum napellus yields an alkaloid aconite used for rheumatism and as nerve sedative. Thallicirom yields mamira. It is used in the treatment of ophthalmia. Some species of Clematis are used as a remedy for leprosy and blood diseases. Juice of some sp, of ranunculus used for intermittent fever. Roots of Hydrastis canadensis are used as antidote of snake bite.

3-Condiments:

Some members are used as condiments for flavoring. Seeds of Nigella (Black fennel, Kala jeera) are used as drug for bronchial asthma, fever and cough

4-Importance for honey:

Most members of this family have nectaries. Flower nectaries have great importance for honey bees for honey production.

5-Poisonous species:

Some members of this family produce acrid juice. It is highly poisonous.

Ranunculaceae family plants

The family, Ranunculaceae is also known as buttercup family, it's comprises about 2252 species in 62 genera of flowering plants. The members of this family are mostly herbaceous plants and distributed in worldwide. The flower of Ranunculaceae family show five or more petals and numerous pistil and stamens. Many species of Ranunculaceae family are used as ornamentals.

List of Ranunculaceae family plants is as follow:

buttercup (genus Ranunculus)
clematis (genus Clematis)
columbine (genus Aquilegia)
globeflower (genus Trollius)
goldenseal (Hydrastis canadensis)
hellebore (genus Helleborus)
- Christmas rose (H. niger)
hepatica (genus Hepatica, sometimes placed in Anemone)
larkspur (genus Delphinium)
love-in-a-mist (Nigella damascena)
marsh marigold (Caltha palustris)
meadow rue (genus Thalictrum)
monkshood (genus Aconitum)
mousetail (genus Myosurus)
pheasant’s-eye (Adonis annua)
winter aconite (genus Eranthis)

Secondary Growth In Stem

2020-08-18T13:48:00.004+05:30

Secondary Growth In Stem

Many species of plant complete their life cycle using only the primary tissues generated by primary meristems. These are the herbaceous species described in Topic C3. In many other species, production of primary tissue and elongation growth are followed by the deposition of secondary tissue. These tissues give increases in diameter and the tissues formed are strengthened in comparison to primary tissues by deposition of extensive secondary walls and lignin, a polymeric phenolic compound, in the cell wall making them woody. Live for many years plants show secondary growth, the wood making them resistant to damage by herbivores and weather. Monocot do not normally generate secondary tissues, but some, like palm trees, undergo additional primary growth to form thick stems. Some palms also continue cell division in older parenchyma tissue to give what is known as diffuse secondary growth.

Vascular Cambium and Cork Cambium

The vascular cambium is a narrow band of cells between the primary phloem and xylem (Fig. 1), which remains a meristem. This tissue goes on dividing indefinitely with active growth in spring and early summer in temperate trees, with the new cells being formed to the outside of the cambium to form phloem and the inside to form xylem (Fig. 2). The newly formed secondary phloem and xylem function like the primary vascular tissue in transport. As xylem cells are deposited on the inner face, the vascular cambium moves outwards. In temperate regions early in the growing season, the cambium produces xylem cells of large diameter and these get progressively smaller as the season progresses. In consequence, growth appears as more and less dense bands of cells, the familiar annual rings observed in cross section of a tree trunk. The cork cambium arises within the stem cortex and generates cuboid cells that quickly become filled with the waxy substance suberin (also found as water-proofing in the root endodermis; Topic I1). The dead cells remain as a protective layer (Fig. 3) but the subernized cells die, required because the original epidermis can no longer function. Cork tissue forms part of the bark of the tree (the remainder being secondary phloem) and replaces the epidermis. Its character and thickness varies from species to species. Some gas exchange to the stem occurs through lenticels, pores remaining through the bark.

Wood anatomy

After the studied of transverse section of a tree trunk (Fig. 3), a number of features appear.

Concentric circles of annual growth rings are evident in most trees from seasonally varying environments. The center of the trunk of many species is the heartwood, where the vascular system no longer functions. It provides structural support and is often darker and impregnated with tannins (Topic J5), but may be completely removed without killing the tree. Around the heartwood lies the sapwood that contains functional phloem and xylem. Vascular rays radiate from the center of the trunk.

These are formed of long lived parenchyma cells which conduct nutrients and water across the trunk, crossing both phloem and xylem, and are responsible for secretions into the heartwood. The outermost layers of the trunk are known as bark. Bark includes the corky tissues produced by the cork cambium and the underlying layers outside the vascular cambium, including the secondary phloem.

HERBARIUM MEANING | HERBARIUM IN INDIA

2020-08-15T12:31:00.003+05:30

HERBARIUM MEANING

Herbarium is a collection of pressed and dried plant specimens mounted on appropriate sheets, arranged according to some known system of classification and kept in pigeon holes of steel or wooden cupboards usually specially prepared for this purpose. There are thousands of plants in the universe and it is not possible to identify them without assigning them in a definite system. This was the beginning of the systematic botany and arrangement of plants in definite system is one of the steps of the process. Before arranging them it is necessary to collect plants according to certain system. The collected plant is the plant specimen and the specimens are the prime sources for floristic studies. Plant materials must be carefully selected, collected and preserved in such a way that they provide a clue for identification and later arranged accurately for classification. The preserved specimen becomes a permanent record for investigation. This is herbarium specimen.

The science of creation of herbarium started way back in the 16th century when Luca Ghini (1490-1556) developed the first Herbarium.

The concept of preserving plant specimens in dried form is 450 years old. The plants were presented in this way by him and the first herbarium of the world was established in 1545 in University of Padua, italy. The first Botanic Garden was also established in the same year. Tourneforte around 1700 used two terms as an equivalent to Hartussiccus, which was later on adopted by Linnaeus. In the middle of 16th century three students of Ghini namely Aldrovondi, Cesalpino (from Italy) and Turner (from England) also made their herbaria.

John Falconer prepared Herbarium in 1553.Dioscorides‘s ―Materia Medica‖ includes an account of the medicinal use of about 100 plants. In Italy, the Italians began teaching Botany and developed the first ever botanical garden When the Renaissance developed,

TOOLS FOR HERBARIUM

The tools used in making herbarium are given below:

 Pocket knife
 Pruning sheets
 Newspaper
 Plastic bags or vasculum (metal box)
 Plant press (Plywood / Iron)
 Digging Tool
 Field note book
 Lead pencil
 Lox hand lens
 String tags
 Collecting vials & jars
 Fixing solution
 Field note book

Field Equipments

 Field Equipment & Tools

* All-Pro Trowel
* Clippers
* Field Bags
* Forceps
* Hori-Hori
* Manual Cover
* Light-Duty Bags

 Pressing

* Presses
* Blotting
* Ventilators
* Straps.
* Newsprint
* Polyurethane Foam

 Mounting

* Mounting Papers
* Adhesives
* Levels
* Bryophyte Packets
* Fragment folders
* Seed Envelopes
* Bond Paper
* Display Envelopes

 Storage & Filing

* Genus Covers
* Species Folders
* Binding Tape
* Cabinets
* Bin Boxes
* Shelf Markers
* Insect Traps
* Humidity Indicators
* Zip-lock Style Bags
* Cartons

 Optics

* Hand Lenses
* Microscopes

 Books

* Presses
* Blotting

TECHNIQUES IN COLLECTION

Making of herbarium involves collection,
drying, poisoning, mounting, stitching,
labeling and deposition etc.

Collection

Angiospermic material must be chosen that
should have leaves, complete inflorescence,
flower and fruit etc. If necessary one has to make many visits to the spot. Size of the material depends upon the requirement and availability. Herbaceous small plant may be collected in 2-2, i.e., with roots also, but in woody plants 4-6 twigs are sufficient.The collection should be given a field number. The species should have at least 4-6 specimens with same field number. Some tools are rather important while collecting up plants for herbarium: A small knife, scissors, thornproof gloves and a small handy spade could be of great help. The collected specimens should be put into a strong bag made of cloth or polythene, the function of these containers being to protect plants from damage during your collection visit. If your excursion takes place in summer time or lasts for two or more days, it is better to bring a folder of approximately 45x30 cm or more. The folder can be covered with cloth and it should be closed with straps or belts, and a handle or shoulder-belt should be added for easy carrying.

Field Note

Date of collection, location (name of place or distance from definite point)), collection number, if possible, name of the specimen, and description of the floral parts that may change after drying are noted down. The good quality specimens also become worst if it does not have good field record. The range, latitude and longitude as well as ecology of the plant need to be noted down by GPS (Global Positioning System) and eyesight vision. Duplicate specimens of one species that are collected on the same date and same locality should be given the same collection number.

Taking Pictures

Taking color pictures of each plant in its natural environment is also something which could substantially enrich the quality of herbarium. In that way the dried specimen can be placed together with one or more photographs, which are very helpful for bulky plants like trees or bushes, which obviously cannot be entirely included in a herbarium.

The suggested equipment is a 35 mm. single lens reflex camera, with a standard lens and a macro-lens, the latter very useful for close ups of flowers and other specific features. A tripod can also alleviate the need for a flash, which may be used when taking pictures in low light, but has the disadvantage of giving quite unnatural looking images.

Each photograph you take should be recorded in a note-book to provide further data for the classification and to include in the herbarium. Be careful that your camera and films are not damaged by rough handling and do not become wet.

Pressing

Generally specimens are kept with in the newspaper.Parts of flower are much carefully spread without overlapping in original shape. If the specimens are long, then it needs to be folded in V and N or Z shape.

Unnecessary overlapping of leaves and other parts must be avoided. If pinnately compound, a branch is only kept. A few leaves may be turned over to show lower and upper view. Specimens should be of good quality with good field note. Collection numbers have also to be written in the flimsies (newspaper or blank newspaper). The standard size of the press is 30 x 45 cm. If the specimen is gymnosperms, the specimens needs to dip in the glycerine before pressing. In case of flowers with gamopetalous corolla a few flowers should be pressed separately and some of these should be split open and spread. The specimens thus kept inside flimsies, are covered on either side by blotters and then it is put in herbarium press. After press is filled or all the specimens are put in the press, the plant press is closed and pressure is applied by means of tightening the straps. Hard and dried fruits and cones need not to be preserved or pressed, but have to be kept in special boxes.

Drying

Drying techniques are of two types; those accomplished without heat, and those with the aid of artificial heat. It is accomplished by means of heated dry air passing up and through the canal of the corrugate. It provides air passages through the press for movement of dry heated air. The most common method of drying is without applying heat. No corrugates are used. The press is locked up for about 24 hours. This is known as the sweating period. It is then opened, and as blotters are removed each pressing sheet is turned back, the specimens are examined, and parts rearranged as the situation demands.

After rearrangement the folder sheet is lifted on to a fresh dry blotter and covered by another dry blotter. A third change of blotters follows usually after 2 to 3 days. Blotters must be changed 3-4 times; every wet blotter removed must be dried, usually by placing in the sun and reused. About a week is required for completion of drying. Dried specimens are packed with much care.

Poisoning

Precaution should be taken to protect herbarium specimens from damage by insect pests. The most destructive insects are herbarium beetle, cigarette beetle, booklice and silverfish. Insect repellants such as naphthalene ball or Para dichlorobenzene are sometimes placed in small quantities in herbarium cabinet. Although dangerous and hazardous to health, mercuric chloride is believed to be valuable because it provides long –term protection against insect attack. Besides the insect pest, the moulds and mildew are constant threat to material stored in damp condition or in areas of high humidity. Naphthalene and LPCP are believed to have fungicidal properties. However, thymol is quite effective as a fungicide.

Mounting

A process in which a species is attached to a Herbarium sheet is and a label affixed at the lower right corner is called Mounting. Specimen mounted on standard size of Herbarium sheet (29×43cm). Most herbaria use a glue or paste to fasten specimens to the sheets. The specimen may be attached by various methods.

Label

The size and shape of label may vary slightly but will usually be a rectangular and range between 10 x 15 cm (4 x 6 in.). The best position for the main label is generally thought to be the bottom right; this makes the label easier to read when kept in genus covers which open on the right hand side.

Generally herbarium label should contain the following information-

1. Heading- name of the institution in which the specimens originated /deposited.

2. Scientific name- Genus, specific epithet, author, or authors

3. Family-

4. Locality-

5. Range, latitude and longitude-

6. Habitat-

7. Date of collection-

8. Name of collector(s)-

9. Determined by-

10. Remarks-

Preservation of Specimens

Heating repellant and fumigants are used to check the attack of such destructive agents. The specimens may be treated by heating in a specially constructed cabinet at 60 0C for 6 hours, which kills larvae, eggs etc. A common process is-Ethylene dichloride mixed with one part of CCl4 (carbon tetrachloride) used for fumigation in closed chamber, which is effective process.

DDT (Dichloro Diphenyl Trichloroethane) is an important insecticide and it is dusted.

Problems in Management

A national herbarium like the Central National Herbarium (CAL), Herbarium of the Forest Research Institute Dehradun, and the Herbarium of the National Botanical Research Institute, Lucknow are critically endangered due to lack of sufficient trained manpower facility.

Herbarium requires large building, curators, collection, tables for researchers and funds for continuous exploration. Funds are not provided for this subject now- a- days so it becomes very difficult to maintain. Policy makers must realize this and efforts should be made to maintain the important herbaria and Taxonomists should come up for exploration and maintenance of herbarium.

Important Herbaria in India

Some major Herbarium in India is as follow :

Steps For Herbarium Preparation

– Preparation of specimen

– Drying of specimen

– Preservation of specimen

– Mounting of the specimen

– Labeling of the specimen

– Filing of the specimen

Collection - Drying - Preservation - Mounting - Labeling – Filing

Functions of Herbarium

A modern Herbarium serves valuable functions or utility. The following are few important functions of a herbarium are:

1. It provides necessary information for verifying and identifying newly collected plants.

2. It is an invaluable conservatory of plant material and data.

3. It is storehouse of collections including the valuable type specimens.

4. Serves as a fundamental resource for identification of all plants of the world.

5. It serves as a source for collection of biodiversity. Most estimates on global biodiversity today are based on herbarium collection only.

6. It aids in biodiversity monitoring by carrying out security of herbarium collection to obtain quantitative baseline data on the distribution and abundance of keystone species is essential for all monitoring programmes.

7. It serves as a repository of voucher specimens on which various botanical researches are carried out.

8. Aids in assessment of conservation status of a taxon.

10. It serves as a source for search of new genetic material for improvement of cultivated stock.

11. It helps in development of computer database on plants and maintains active links to international networks of systematic resources and electronic database.

12. It provides research facilities to the students of taxonomic research.

13. It provides complete idea of vegetation and place of origin of plants.

14. The ecological, economical and ethnobotanical data may be obtained, and

15. It provides key for the preparation of modern system of classification.

The herbaria are classified as:

(a) Major or National Herbaria which cover the flora of the world and serve the purpose of research as well as identification.

(b) Minor Herbaria which include smaller herbaria such as Regional herbaria, local herbaria and College / University herbaria.

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