Plant hormones

Question 1

what are auxins and what do they do

Answer 1

a plant growth hormone which controls growth near the tips of SHOOTS AND ROOTS

Question 2

what is a positive tropism

Answer 2

when a plant grows towards the stimulus ( change in environment)

Question 3

what is a negative tropism

Answer 3

the plant grows away from the stimulus

Question 4

what is phototropism

Answer 4

a response to the stimulus of light

Question 5

what is geotropism

Answer 5

a response to the stimulus of gravity

Question 6

how do shoots use auxin to grow towards the light

Answer 6

1. auxin is produced at the very top of the shoot
2. in shoots, auxin triggers cell growth
3. light causes auxin to concentrate on the darker side of the shoot tip
4. auxin now spreads down the shoot, so cells on the darker side grow faster than cells on the lighter side
5. this causes the shoot to grow towards the lught

Question 7

what direction to plant roots grow

Answer 7

towards the force of gravity

Question 8

what is photo and geotropism caused by

Answer 8

• unequal distribution of auxin

Question 9

what happens when shoots grow towards light

Answer 9

• when a shoot tip is exposed to light, more auxin increases on the side that is in the shade than the side thats in the light
• this makes the cells grow and elongate faster on the side in the shade, so the shoot bends towards the light

Question 10

describe geotropism

Answer 10

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

Question 11

what do gibberellins do

Answer 11

they stimulate plant stems to grow, they are important for seed germination

Question 12

what is seed germination

Answer 12

the process where seeds sprout and begin to grow

Question 13

what can gibberellins be used for

Answer 13

ending / controlling seed dormancy
promote flowering
increase fruit size

Question 14

what is seed dormancy

Answer 14

when seeds will not germinate because of certain conditions, e.g - coldness or dryness

Question 15

what is ethene and what is it used for in plants

Answer 15

a gas produced by aging parts of a plant, used to stimulate the ripening of a fruit

Question 16

what are auxins used for in agriculture

Answer 16

• killing weeds
• as rooting powders
• for growing cells in tissue culture

Question 17

what would happen if the tip of a shoot is removed

Answer 17

no auxin available so shoot may stop growing

Question 18

what does extra auxin do

Answer 18

promotes growth in the shoot but inhibits growth in the toot

Question 19

what experiment was used to investigate phototropism

Answer 19

1. shine light on shoots
2. the shoots will grow in the direction of the light
3. cut off the shoots tips
4. shoots did not grow towards the light
5. scientists suggested the shoot produced a hormone (auxins)
6. scientists covered tips of shoots with foil and they didnt grow towards the light, suggesting that the tips are sensitive the light
7. they covered the lower parts of the shoots with foil, and the shoots grew towards the light, showing that the lower parts of shoots were not sensitive to the light

Question 20

why is ethane used

Answer 20

Fruits, such as bananas, are usually harvested before they are ripe. These are then transported long distances and can be stored before they’re needed. Ethene is then used to trigger bananas to ripen just before they’re sold in the uk