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
 

 

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