Plant Responses - Growth Hormones

Question 1

Why do plants respond to changes in their environment?

Answer 1

to increase their chances of survival e.g. towards light to increase rate of photosynthesis

Question 2

What is tropism?

Answer 2

the response of a plant to a directional stimulus

directional stimulus - coming from a specific direction

Question 3

Describe growth hormones in plant response

Answer 3

plants respond to stimuli by using growth hormones
they dont have a circulatory system to respond using hormones or
nervous system using nerves
e.g. auxins (IAA) - in shoots - cause cell elongation - not cell division
e.g. gibberellins - controlling flowering and germination
they are made in the growing regions of the plant - root and shoot tips
move short distances by diffusion and active transport
move long distances in the phloem

Question 4

What are the two types of tropism?

Answer 4

phototropism - response to light

geotropism - response to gravity

Question 5

What happens to IAA in phototropism?

Answer 5

• IAA is always going to move to the shaded side of root/shoot
• shoots - IAA causes cell elongation - shoots grow towards light
• roots - IAA inhibits cell growth - roots grow away from light

Question 6

What happens to IAA in geotropism?

Answer 6

• IAA always moves to the underside
• shoots - goes to underside - cell elongation - grows away from gravity
• roots - grows towards gravity