response to stimuli: plants

Question 1

why do plants need to be able to grow in response to light?

Answer 1

to ensure their leaves can absorb light for photosynthesis

Question 2

why do plants need to be able to grow in response to gravity?

Answer 2

to ensure that shoots grow upwards and roots grow downwards

Question 3

what are tropisms?

Answer 3

the directional growth responses made by plants in response to light and gravity

Question 4

if the growth is towards the stimulus what is the tropism?

Answer 4

positive

Question 5

if the growth is away from the stimulus what is the tropism?

Answer 5

negative

Question 6

what is growth towards the light?

Answer 6

a positive phototropism

Question 6

what are phototropisms?

Answer 6

growth responses to light from one direction

Question 7

what hormone controls the positive phototropism?

Answer 7

auxin

Question 8

where is auxin found?

Answer 8

in the tip of the shoots and the roots

Question 9

what is a response to gravity?

Answer 9

geotropism

Question 10

why do roots grow downwards into the soil?

Answer 10

• to anchor the plant
• absorb water and minerals from the soil

Question 11

what does auxin do?

Answer 11

coordinates and controls directional growth responses such as phototropisms and geotropisms

Question 12

what does auxin do in the shoots?

Answer 12

promotes cell elongation

Question 13

what does auxin do in the roots?

Answer 13

inhibits cell elongation

Question 14

what is the distribution of auxin in the shoots affected by?

Answer 14

light and gravity

Question 15

what is the distribution of auxin in the roots affected by?

Answer 15

primarily affected by gravity alone

Question 16

what does the unequal distributions of auxin cause?

Answer 16

unequal growth rates in plant roots and shoots

Question 17

what side does auxin accumulate on?

Answer 17

the dark side

Question 18

what happens if the shoot is growing in uniform light?

Answer 18

• auxin distributed evenly on each side of the shoot
• mitosis is even on each side- shoot grows upwards

Question 19

what happens if the shoot is growing in unidirectional light?

Answer 19

• auxin diffuses and accumulates on the dark side
• faster elongation
• more mitosis- bends towards the sunlight

Question 20

compare unidirectional and uniform light?

Answer 20

• unidirectional- stimulus is on one side
• uniform- light is evenly distributed

Question 21

what is the radicle?

Answer 21

the root

Question 22

what is the plumule?

Answer 22

the shoot

Question 23

what happens to the plant if light shines all around the tip?

Answer 23

auxin is distributed evenly throughout and the cells in the shoot grow at the same rate