16.4 Tropisms in plants

Question 1

what is a tropism?

Answer 1

plant growth repsonses to stimuli

Question 2

what is phototropism?

Answer 2

growth of plants in response to light

Question 3

what is geotropism?

Answer 3

growth of plants in response to gravity

Question 4

what causes phototropism?

Answer 4

diffusion of auxin across roots and shoots due to varying exposures to light

Question 5

how is auxin transported over short distances?

Answer 5

diffusion

Question 6

how is auxin transported over long distances?

Answer 6

by the phloem

Question 7

how does auxin cause growth in the roots and shoots?

Answer 7

it causes cell elongation on the side it is most present on

Question 8

are shoots positively or negatively phototropic?

Answer 8

POSITIVELY
as the shoots grow TOWARDS the stimuli

Question 9

are roots positively or negatively phototropic?

Answer 9

NEGATIVELY
as they grow away from the stimuli

Question 10

what causes a plant to grow towards light?

Answer 10

auxin on the the side exposed to the light diffuses laterally to the shaded side

as there is more auxin on the shaded side there is more growth which leads to the shaded side elongating and causing it to bend towards the light

Question 11

how do auxin concentrations change with light?

Answer 11

THEY STAY THE SAME
no auxin is destroyed
auxin moves by diffusion

Question 12

what happens to a plant’s response to light when the shoot tip is removed?

Answer 12

there is not shoot growth

as the shoot tip detects the stimuli, and produced the auxin needed for growth

Question 13

what happens to a plant’s response to light when the shoot is covered?

Answer 13

there is no shoot growth

as the shoot tip cannot detect the light as it is covered

Question 14

what is mica?

Answer 14

impermeable gel which prevents hormones passing through

Question 15

what happens to a plant’s response to light when mica is added to the illuminated side?

Answer 15

shoot bends towards the light

as the auxin cannot pass down the illuminated side to the mica, it passes down the shaded side which causes elongation and growth

Question 16

what is a gelatin block?

Answer 16

permeable gel which allows hormones to pass through

Question 17

what happens to a plant’s response to light when a gelatin block is added?

Answer 17

normal phototropic response
bends towards light

Question 18

what was the original theory about the affect of light on auxin?

Answer 18

originally thought that auxin was BROKEN DOWN by light

Question 19

what has disproved the original theory on light’s affect on auxin?

Answer 19

auxin levels regardless of the direction of light stay the same

Question 20

which hormone causes plants to grow in the dark?

Answer 20

gibberellins as they lead to extreme elongation of the internodes

Question 21

what is etiolation?

Answer 21

growth of a plant in the dark

Question 22

what is geotropism?

Answer 22

growth of a plant in response to gravity

Question 23

are shoots positively or negatively geotropic?

Answer 23

NEGATIVELY
as they grow away from gravitational pull UPWARDS

Question 24

are roots positively or negatively geotropic?

Answer 24

POSITIVELY
as they grow towards gravitational pull DOWNWARDS

Question 25

what does geotropism ensure?

Answer 25

roots grow down into the soil
shoots grow up into the sky

Question 26

why is it important for roots to grown into the soil?

Answer 26

can reach water stores in the soil

Question 27

why is it important for shoots to grow up into the sky?

Answer 27

can reach more light for photosynthesis