Topic 6 - Plant Responses

Question 1

how do plants respond to stimuli?

Answer 1

they respond to chsngers in their environment, the presence of predators and abiotic stress (e.g. drought)

Question 2

what are auxins?

Answer 2

plant hormones which control growth at the tips of shoots and roots

Question 3

where is auxin produced?

Answer 3

in the tips of the plant, but it diffuses backwards to stimulate the cell elongation process which occurs in the cells behind the tips - promoting growth in the shoot but inhibiting growth at the roos

Question 4

how are shoots positively phototropic?

Answer 4

when a shoot is exposed to light it accumulates more auxin in the shaded side. this makes the cells elongate faster on the shaded side, so the shoot bends towards the light

Question 5

how are shoots negatively geotropic?

Answer 5

when a shoot grows sideways, gravity produces more auxin on the lower side, causing the lower side to grow faster, bending the shoot upwards

Question 6

how are roots negatively phototropic?

Answer 6

when a root is exposed to light it accumulates more auxin in the shaded side. this inhibits cell elongation on the shaded side, so the shoot bends away from the light

Question 7

how are roots positively geotropic?

Answer 7

when a shoot grows sideways, gravity produces more auxin on the lower side, inhibiting growth on the lower side, so the root bends downwards