14.2 pant growth factors

Question 1

what is it called when something grows towards light?

Answer 1

positively phototropic

Question 2

what is it called when something grows away from light?

Answer 2

negatively phototropic

Question 3

what is it called when something grows away from gravity?

Answer 3

negatively gravitropic

Question 4

what is it called when something grows towards gravity?

Answer 4

positively gravitropic

Question 5

what is it called when something grows towards water?

Answer 5

positively hydrotropic

Question 6

what is it called when something grows away from water?

Answer 6

negatively hydrotropic

Question 7

give an example of a plant growth factor

Answer 7

indoleacetic acid (IAA)

Question 8

are plant roots positively or negatively phototropic?

Answer 8

negatively phototropic

Question 9

are plant roots positively or negatively gravitropic?

Answer 9

positively gravitropic

Question 10

are plant roots positively or negatively hydrotropic?

Answer 10

positively hydrotropic

Question 11

are plant shoots positively or negatively phototropic?

Answer 11

positively phototropic

Question 12

are plant shoots positively or negatively gravitropic?

Answer 12

negatively gravitropic

Question 13

are plant shoots positively or negatively hydrotropic?

Answer 13

negatively hydrotropic

Question 14

what group of substances does IAA belong to?

Answer 14

auxins

Question 15

role of IAA in elongation growth

Answer 15

• active transport of H^+ from the cytoplasm in the cell wall
• increase plasticity allowing the cell to elongate by expansion

Question 16

what is the acid growth hypothesis?

Answer 16

proposed explanation of how IAA increases the plasticity of young cells

Question 17

what does IAA do to shoots?

Answer 17

IAA stimulates growth in shoots

Question 18

what does IAA do to roots?

Answer 18

IAA inhibits growth in roots

Question 19

explain how the movement of IAA in shoots helps a plant to survive

Answer 19

• IAA moves towards the shaded side
• cells on the shaded side elongate faster than those on the light side
• shoot bends towards the light
• ensures that the shoot and leaves are in the sunlight
• needed for photosynthesis

Question 20

suggest 2 advantages to a plant of having roots that respond to gravity by growing in the direction of its force

Answer 20

response ensures that roots grow down into the soil, anchoring the plant firmly and bringing them closer to water which is needed for photosynthesis