Organisms Respond to Changes in Environment (Year 13 Content)

Question 1

Explain why shoots show positive phototropism

Answer 1

1) IAA is formed in the shoot of the plant
2) It diffuses evenly down the plant
3) Light causes diffusion of IAA to the shaded side of the shoot
4) There is a higher concentration of IAA on the shaded side
5) IAA causes cell elongation on the shaded side of the shoot
6) Shoots bend towards the light

Question 2

Explain why roots show positive geotropism

Answer 2

1) Gravity causes the accumulation of IAA on the lower side of the root
2) IAA inhibits cell elongation on the lower side of the root
3) Cells on the upper side elongate faster so bend down