Effect of unilateral light, growing in the dark, & geotropisms Flashcards
1
Q
Why is there more auxin on the shaded side?
A
- light causes auxin to move laterally across the shoot
- so conc is greater on the unilluminated side
2
Q
How does the auxin cause the plant to bend towards the light?
A
- cell elongattion on shaded side and growth
- causes the shoot to grow directly towards the light
3
Q
What happens once the shoot is growing directly towards the light?
A
- unilateral stimulus is removed
- transport of auxin stops
- shoot grows straight towards the light
4
Q
What happens to the growth of plans in the dark?
A
- grow more rapidly in the dark than when they are illuminated
5
Q
Why do plants grow more in the dark?
A
- biological imperitive is to grow upwards rapidly to reach the light to be able to photosynthesis
- slowing of upwards growth when exposed to light is valuable
- resources used for synthesising leaves and strengthening stems
6
Q
What causes growth in the dark?
A
- gibberelins
- extreme elongation of the internodes
- level of gibberelins fall when the plant is exposed to light
7
Q
Why is growth in the dark important?
A
- some farmers force growth in the plants in the dark
8
Q
How do seedlings respond to gravity?
A
- shoots grow away
- negative geotropism
- roots grow towards
- positive
- even when placed on sides in all round light or in dark
