Phytohormones

Phytohormone

5.2

Phytohormone

Types and functions of phytohormones:

Phytohormone	Function
Auxin	Stimulates shoot growth and growth Stimulates root growth at low concentration Stimulates fruit development after fertilisation Inhibit growth of lateral buds Inhibits root growth at high concentration Delay senecence of fruits and leaves
Gibberellin	Stimulates cell elongation at stem Stimulates seed germination Stimulates development of certain fruits
Cytokinin	Stimulates cell division in the presence of auxin Stimulates growth of lateral buds Delays senescence of leaves
Abscisic acid	Stimulates closing of stomata during water stress Inhibits seed germination
Ethylene	Stimulates ripening in fruits Stimulates senescence of fruits and leaves

Phototropism and geotropism are two main types of tropisms which can be shown by shoot and root:

Phototropism is the growth of plant parts which can respond towards light
Geotropism is the growth of plant parts which can respond towards gravity

Tropism	Stimulus	Response
Positive phototropism	Unilateral light	Shoot bend towards the light
Negative phototropism	Unilateral light	Root bends away from the light
Positive geotropism	Gravity	Roots grow downward to the gravitational pull
Negative geotropism	Gravity	Shoots grow upward away from the gravitational pull