Coordination in plants

Coordination in plants :-

In plants control and coordination is done by chemical

substances called plant hormones or phytohormones.

There are five main types of plant hormones. They are :-

Auxins, Gibberillins, Cytokinins, Abscisic acid and

Ethylene.

i) Auxins :-help in cell division, cell elongation and

growth.

ii) Gibberillins :-help in growth of stem and branches.

iii) Cytokinins:- help in cell division, formation of fruits and

seeds.

iv) Abscisic acid :- inhibits growth and affects wilting of

leaves.

vi) Ethylene :- helps in flowering and ripening of fruits.

6) Movements in plants :-

Movements in plants are of two main types. They are :-Tropic movements and Nastic movements.

a) Tropic movements :- are directional movements towards or

away from the stimulus and it depends on growth. They are of

different types like Phototropism, Geotropism, Chemotropism,

Hydrotropism etc.

i) Phototropism :- is movement of plants in response to light. If it is

towards light, it is called positive phototropism. Eg:- Bending of

shoot towards light. If it is away from light, it is called negative

phototropism. Eg:- Bending of root away from light.

ii) Geotropism :-is the movement of plants in response to gravity. If it is

towards gravity it is called positive geotropism. Eg:- Downward

growth of roots. If it is away from gravity it is called negative

geotropism. Eg:- Upward growth of shoot.

iii) Chemotropism :- is movement of plant in response to chemical

stimuli. Eg:- Growth of pollen tube towards the ovule.

iv) Hydrotropism :- is the movement of plants in response to water.

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