26.1 tropisms and auxins

Question 1

tropisms

Answer 1

• a growth movement of part of a plan in reponse to a directional stimulus

Question 2

what factors do plants respond to

Answer 2

1) light
2) gravity
3) water

Question 3

what is light tropism called

Answer 3

• phototropism

Question 4

what is gravity tropism called

Answer 4

• geotropism

Question 5

what is water tropism called

Answer 5

• hydrotropism

Question 6

what part of the plant is positively phototrophic

Answer 6

• stems

- because light is needed for photosynthesis

Question 7

what part of the plant is positively geotropic

Answer 7

• roots
• they are sensitive to gravity and grow in the direction of its pull
• in order to firmly anchor a plant in the soil

Question 8

what part of the plant is positively hydrotropic

Answer 8

• roots
• in order to absorb water needed for photosynthesis, metabolic reactions, turgidity of stem and to produce cellular structures (cytoplasm)

Question 9

what is IAA

Answer 9

• plant growth factor that causes elongation of the shoot - it is an auxin
• indoleacetic acid (IAA)

Question 10

IAA and shoot response to light

- 5 stages

Answer 10

1) - cells in the tip of a shoot produce IAA which is then transported down the shoot
2) - initially the IAA is transported to both sides of the shoot as it begins to move down
- however light causes the IAA to move from the light side to the shaded side of the shoot
3) - IAA then builds up on the shaded side of the shoot - more concertration of IAA in that side
4) - the side with more IAA will then start to elongate more and the darker side of the shoot will grow faster
5) - shoot bends towards light

Question 11

IAA and root response to gravity

Answer 11

-