4.5.4.1 Control and Coordination Flashcards
1
Q
What do plants need hormones for?
A
- coordinate and control growth
- needed for tropisms
2
Q
What are examples of tropisms?
A
- phototropism
- gravitropism/geotropism
3
Q
What is phototropism?
A
- response to light
4
Q
What is gravitropism/geotropism?
A
- response to gravity
5
Q
Why do hormones move?
A
- move to where they are needed in order to produce appropriate response
6
Q
What is positive phototropism?
A
- most plants show this
- plant grows towards light source
- plant is exposed to light on one side
- auxin moves to shaded side
- auxin stimulates cells to grow more
- shoot bends towards light
- plant receives more light, meaning faster rate of photosynthesis
7
Q
What is negative gravitropism?
A
- most shoots show this
- grow away from gravity
- shoot is horizontal:
- auxin moves to lower side
- cells of shoot grow more on side with most auxin
- makes shoot bend and grow away from ground
- beneficial as light levels are likely to be higher further away
8
Q
What is positive gravitropism?
A
- most roots show this
- root is horizontal:
- auxin moves to lower side
- cells of root grow more on side with less auxin
- stimulates cells to grow on upper side
- makes root bend and grow downwards
- beneficial as there are more likely to be increased water levels and nutrient levels
9
Q
What happens when auxin distribution becomes equal on both sides?
A
- grows straight in that direction
10
Q
What are two other plant hormones?
A
- gibberellins
- ethene
11
Q
Why are gibberellins important?
A
- to stimulate seed germination
12
Q
What is ethene involved in?
A
- cell division
- ripening of fruits
