Phytohormones

PHYTOHORMONES

PRESENTED BY:- SHIYAS

HORMONES 

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Chemical that transfers information and instructions between cells in animals and plants Hormones act more slowly, and their effects typically are maintained over a longer period of time. Required in very low concentration. Synthesized at one part and translocated to another for their action.

PHYTOHORMONES

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Also called growth hormones. A hormone produced naturally by plants that activates or regulates their growth. The synthetic equivalent used to promote growth in cultivated plants are called as growth

TYPES 

Different types:Auxin  Gibberellins  Cytokinins  Ethylene  Abscisic acid  Jasmonic acid  Other hormones 

AUXIN    

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Auxin (Gk. auxein=to grow). First to be discovered. Name Auxin given by WENT(1928). First auxin isolated from human urine and was named heteroauxin, chemically it was indole 3 acetic acid (IAA). Weakly acidic Capable of cell

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Heteroauxin found in humans suffering from pellagra, a disease caused by deficiency of niacin (vitamin B5).

TYPES 

Natural Auxins :-

a tissue or organ in the earliest stage of embryonic development, found when the dividing cells in the fertilized ovum first differentiate .

Phytohormones  Synthesized in leaf primordia, shoot apices and developing seeds.  Show polar movement.  Move slowly by diffusion from cell to cell  Optimum concentration: 

Shoots :10ppm  Roots : 0.0001ppm 

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Examples : IAA  3 acetaldehyde  4-chloro-idole acetic acid 

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Synthetic Auxins :-

Artificially made.  Cause similar responses common to IAA.  Move in all directions.  Eg:

2,4-D  IBA (Indole Butyric Acid)  NAA (Naphthalene 

FUNCTIONS  

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Cell enlargement Cell division in cambium Root growth (low conc.) Apical dominance Cause phototropism Parthenocarpic fruits (banana) Synthesis of ethylene ( high conc. IAA) Respiration (stimulate)

USES    

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Eradication of weeds (2,4-D) Rooting stem cuttings (IBA ,NAA) Parthenocarpy (grapes) Flowering, plants like pineapple, litchi (NAA) Preventing pre harvest fruit drops of orange, apple ,tomato etc.(2,4-D) Prevention of falling of crop plants. (NAAM-Naphthalene acetamide)

GIBBERELLINS 

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Isolated from Gibberlla fujikori by Yabuta(1935). Weakly acidic Cause cell elongation of intact plant. Increase internodal length of dwarfed NODE:the place on a plants plant stem where a leaf Synthesized in is attached or has been attached young leaves near

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They are synthesized from a precursor compound mevalonic acid (derived from acetyl co A). They are transported in plants by simple diffusion and also by conducting channels.

TYPES 

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100 different types have been identified. A single plant posses a no. of gibberellins. They are termed as GA1 (Gibberellic acid), GA2,GA3,GA4 and so on.

FUNCTIONS        

Stem and leaf growth Elongation of genetically dwarf plants (pea, maize) Bolting (cabbage): elongation of internodes. Induce flowering Seed germination (stimulate prod. of hydrolytic enzymes) Development of fruits Induce Parthenocarpy Break dormancy

USES 

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Fruit growth (size, bunch length in grapes) Parthenocarpy (rice, pear) Overcoming dormancy Seed germination (lettuce, tobacco ) Delayed ripening (citrus fruits for storage) Malt yield (increase the yield from barley grains)

CYTOKININS        

They are basic in nature Promote cell division (cytokinesis) Work alone or with auxin Discovered by Miller (1955) in coconut water Skoog gave the term Cytokinins. They are largely found in roots From roots they pass upward via xylem They are synthesized in endosperm of seeds,growing embryos and developing fruits.

TYPES 

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First isolated was ZEATIN (6-hydroxy 3-methyl trans, 2butenyl amino purine) Almost 18 types of Cytokinins are known Miller discovered Kinetin

KINETIN

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6-FURFURYLAMINO-PURINE

FUNCTIONS        

Cell division Cell elongation Morphogenesis Delay in senescence Counter action of apical dominance. Differentiation : Plastid etc Increase resistance from diseases Stimulate enzyme activity especially photosynthesis

SENESCENCE

AGEING OF LEAVES

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Tissue culture. Increasing shelf life of fruits and vegetables. Increasing resistance.

ETHYLENE      

Gaseous hormone Stimulates transverse growth Discovered by Crocker (1935) Produced in plants from methionine. Synthesized in all parts of plants. High auxin conc. also causes ethylene production

FUNCTIONS        

Transverse growth Inhibition of geotropism Fruit ripening Apical dominance Root initiation (low conc.) Stimulate senescence Formation of ABA Flowering (pineapple)

USES 

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Ripening of fruits (ethylene lamps) such as apple, banana, mango etc Increase in number of fruits by increasing no. of female flowers especially in cucumber Sprouting of storage organs such as tubers.

Sprouting of Rhizome

ABSCISIC ACID        

Mildly acidic Growth inhibitor Counter acts all other hormones First isolated by Addicott (1963) He named it Abscisin II Wareing and Cornforth isolated a substance which induced bud dormancy. They named it Dormin. Both abscisin and dormin later were found to be same and named abscisic acid (ABA)

Chemical structure of ABA

FUNCTIONS         

the natural process by which leaves or other parts are shed from a plant

Dormancy of buds and seeds Abscission of flowers and fruits Senescence of leaves by chlorophyll destruction tiny porestress, in the outer layer (epidermis) of a Stomata closure ( during prevents plant leaf or stem that controls the passing of transpiration) water vapour and other gases into and out of the plant. Inhibition of germination Delays flowering Tuberization in potato. Enhances rooting Controlled growth by checking activities of other hormones

USES   

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Antitranspirant Promote rooting of stem cuttings Prolongs dormancy of buds, seeds and storage organs Induce flowering

JASMONIC ACID 

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3-Oxo-2-pentenylcyclopentaneacetic acid It is biosynthesized from linolenic acid A member of the jasmonate class of plant hormones.

FUNCTIONS     

Growth inhibition, Senescence Leaf Abscission Tuber formation in potatoes, yams, and onions. It has an important role in response to wounding of plants and resistance. When plants are attacked by insects, they respond by releasing JA, which inhibits the insects' ability to digest protein

OTHER OTHER HORMONES HORMONES 

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Brassinolides :Plant steroids chemically similar to animal steroid hormones. First isolated from pollen of the mustard family. They promote cell elongation and cell division, differentiation of xylem tissues, and inhibit leaf abscission.Plants found deficient in brassinolides suffer from dwarfism. Salicylic acid :In some plants activates genes that assist in the defense against pathogenic invaders. Systemin : A polypeptide consisting of 18 amino acids, functions as a long-distance signal to activate chemical defenses against herbivores. . Strigolactones: Implicated in inhibition of shoot branching.

BIBLIOGRAPHY  

http://en. wikipedia . org P.K.Garg, J.P.Sharma ; Biology; 2007; Laxmi Publications.

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