plant hormones

Question 1

explain phototropism in shoots

Answer 1

• auxin is produced at the tip of shoots
• in shoots auxin triggers cell growth
• light causes auxin to concentrate on the shaded side of the shoot tip
• auxin spreads down the shoot so cells on the shaded side grow faster than cells on the lighter side
• this causes the shoot to grow towards the light

Question 2

explain gravitropism (geotropism) in roots

Answer 2

• auxin is produced in the root
• gravity causes the auxin to concentrate on the lower side
• in roots auxin inhibits cell growth
• the lower side now grows more slowly than the upper side
• this causes the roots to grow towards the force of gravity (downwards)

Question 3

what does the plant hormone ethene do

Answer 3

the ripening of fruits (controls cell division)

Question 4

what does the plant hormone gibberellins do

Answer 4

start the germination of seeds