Homeostasis - Plant Hormones Flashcards
1
Q
Give 3 examples on how plants can respond to their environment
A
- sense light and point their shoots towards it for photosynthesis
- sense gravity causing their roots to grow downwards to keep them stuck in the ground
- can sense touch + climb around other objects
2
Q
What do plants rely on?
A
hormones (act locally)
3
Q
Describe what auxins do
A
- control growth on ends of shoots and roots
- once produced, they dissolve in the solution of the cells in the shoot
- they then diffuse backwards along the shoot on the root
- they stimulate growth causing shoots to grow, but in roots they inhibit growth
4
Q
What do phototropism and geotropism (gravitropism) respond to?
A
phototropism responds to light
geotropism responds to gravity ‘gravitropism’
5
Q
Describe how phototropism causes the plants to grow
A
- Shoots are positively photorophic (grow towards the light)
- and are negatively gravitropic (grow towards the ground)
- If the sun is on the left side of the shoot, auxins will accumulate on the shaded side
- auxins stimulates growth in shoots, causing cells on the shaded side to grow faster than the ones on the sunny side
- difference in growth rate is what causes the shoot to curve towards the light
- this is because the cells on the right are growing much faster on the right, but not many on the left as their growth has increased
6
Q
Describe how gravitropism causes the roots of a plant to grow
A
Roots are negatively photorophic (away from the light)
Roots are positively gravitropic (towards the ground)
- auxins will accumulate on lower side if root exposed to light
- auxins inhibit growth, upper side will grow faster
- this causes the shoot to grow downwards
7
Q
Name 3 plant hormones and their functions
A
- Auxin - stimulates plants to grow (can kill weeds and disrupt a plant’s growth)
- Gibberellin - controls dormancy, induces flowering, growing larger fruit
- Ethene - Stimulates the ripening of fruit (stimulates an enzyme that causes fruit to ripen)
