Plant growth factors

Question 1

Which changes to plants internal and external environments cause a response?

Answer 1

• shoots grow towards the light for photosynthesis (positively photopropic)
• roots grow towards gravity to anchor themselves in the soil (positively gravotorpic)
• roots grow towards water (positively hydrotropic)

Question 2

What do plant growth hormones do?

Answer 2

• plant growth factors affect the tissues that release them

- auxins and IAA affect the directional growth of a plant

Question 3

What is the sequence of phototropism in flowering plants?

Answer 3

• cells in the tip of the shoot produce IAA,
• light causes movement of IAA from the light side to the shaded side of the shoot
• a greater concentration of IAA builds up on the shaded side of the shoot which causes faster elongation of shoot cells on the shaded side so the shoot bends towards the light

Question 4

How are roofs negatively phototropic?

Answer 4

• high concentrations of IAA inhibits cell elongation in roots
• there fore elongation if cells cells is greater on the light side than on the shaded side and so roots bend away from the light, that is, they are negatively phototrophic

Question 5

What is the sequence of gravitropism in flowering plants?

Answer 5

• cells in the tip of he root produce IAA,
• gravity moves IAA from the upper side to the lower side of the root
• so cells on this side elongated less than those on the upper side causes the roots to bend downwards towards the force of gravity

Question 6

What is negative gravitropism?

Answer 6

• in shoots the greater concentration of IAA on the lower side increases cell elongation and causes this side to elongated more than the upper side
• as a result the shoot grows upwards away from the force of gravity

Question 7

what is plasticity?

Answer 7

-IAA increases the plasticity if cell walks so they can stretch by allowing in hydrogen atoms