Module 5 : Tropisms in plants

Question 1

What is a tropism?
-make 1 additional point about what they are triggered by

What do tropisms allow plants to do?

Answer 1

a directional growth response to a stimulus
-they are triggered by chemical messages

-they allow plants to respond to variations in environmental conditions so that they can make maximum use of the environment for survival

Question 2

What is phototropism and what does it maximise ?

Answer 2

growth towards or away from light

phototropism maximises the ability of plants shoots and leaves to capture light for photosynthesis

Question 3

Define the difference between positive and negative phototropism

Answer 3

positive-when shoots grow towards light
negative-when roots grow away from light

Question 4

What is geotropism?

Give 2 purposes of geotropism to plants

Answer 4

growth towards or away from gravity

-helps a plant establish its shoots and roots in the optimum orientation
-helps roots anchor in soil to provide support as well as to obtain nutrients and minerals

Question 5

Define the difference between positive geotropism and negative geotropism

Answer 5

positive-when roots grow downwards , towards the gravitational pull
negative-when shoots grow upwards , away from the gravitational pull

Question 6

Make 5 points about how auxins control positive phototropism in plants

Answer 6

1)auxin is produced in cells in the tip of the shoot
2)auxin is transported down the plant shoot
3)light stimulates auxins to accumulate on the shaded site of the shoot rather than the side exposed to light
4)auxins become more concentrated on the shaded side and stimulate more cell elongation on the shaded side of the shoot
5)the shoot bends towards the light

Question 7

Make 5 points about how negative phototropism and positive geotropism is controlled by auxins

Answer 7

1)auxin is produced in cells in the tip of the root and is transported along the root
2)any light available stimulates auxin to move to the shaded side of the root
3)gravity also pulls auxin from the upper side of the root to the lower side
4)auxin becomes concentrated in the lower shaded side and inhibits cell elongation in the lower shaded side
5)the root bends away from any light and downwards towards the gravitational pull