Plant responses

Question 1

what is a tropism?

Answer 1

when plants respond, via growth, to stimuli (can be positive or negative)

Question 2

what factors do plants respond to?

Answer 2

gravity, light, and water

Question 3

what is IAA and what does it do?

Answer 3

IAA is a type of auxin which is made in the tips of roots and shoots (but can diffuse to other parts) and it controls cell elongation in shoots whilst inhibiting cell growth in the roots

Question 4

describe the process of a positive phototropism in shoots

Answer 4

the shoot tip cells produce IAA, causing cell elongation, and this diffuses to other cells. in unilateral light, it’ll diffuse towards the shaded side, resulting in a higher IAA concentration. the IAA causes the shaded side to elongate more, so the plant bends towards the light.

Question 5

describe the process of a negative phototropism in roots

Answer 5

a high IAA concentration will inhibit cell elongation, causing root cells to elongate more on the lighter side, so the root bends away from the light

Question 6

describe the process of a negative gravitropism in shoots

Answer 6

IAA will diffuse from the upper side to the lower side of the shoot. if vertical, plant cells will elongate and the plant grows upwards. if horizontal, the shoot will bend upwards.

Question 7

describe the process of a positive gravitropism in roots

Answer 7

IAA moves to the lower side of the roots, so the upper side elongates and the root bends down towards gravity.