T6 -controlling Plant Growth

Question 1

What are plant tropisms?

Answer 1

The growth of a plant to in response to a stimulus

Question 2

What is positive tropism?

Answer 2

The growth of a plant towards a stimulus

Question 3

What are the two main types of plant tropism?

Answer 3

Phototropism
Gravitropism

Question 4

Define phototropism

Answer 4

A plant’s growth response to light

Question 5

Define gravitropism

Answer 5

A plant’s growth response to gravity

Question 6

What are auxins?

Answer 6

• A group of plant hormones involved in plant tropisms
• Control growth in plant roots and shoot tips

Question 7

Where are auxins produced?

Answer 7

Root and shoot tips

Question 8

What is a shoot

Answer 8

A shoot is part of the plant above the ground

Question 9

Compare the effect of auxins in plant shoots and
roots

Answer 9

Auxins stimulate growth in plant shoots
Auxins inhibit growth in plant roots

Question 10

What does inhibit mean

Answer 10

Hold back the growth

Question 11

How do auxins move through a plant?

Answer 11

They diffuse through the plant in solution

Question 12

Are plant shoots positively or negatively phototropic? How does this affect shoot growth?

Answer 12

Positively phototropic
Plant shoots grow towards the light

Question 13

Explain why plant shoots are positively phototropic

Answer 13

• Shoot tip exposed to light
• On the shaded side of the shoot, auxin accumulates
• Elongation of cells on the shaded side
• Shoot tip bends towards the light

Question 14

Are plant shoots positively or negatively gravitropic?
How does this affect shoot growth?

Answer 14

Negatively gravitropic
Plant shoots grow upwards, away from gravity

Question 15

Explain why plant shoots are negatively gravitropic

Answer 15

• Shoot placed horizontally
• Due to gravity, auxin accumulates on the lower side of the shoot
• Elongation of cells on the lower side
• Shoot bends upwards growing away from gravity

Question 16

Are plant roots positively or negatively phototropic? How does this affect root growth?

Answer 16

Negatively phototropic
Plant roots grow away from the light

Question 17

Explain why plant roots are negatively phototropic

Answer 17

• Root exposed to light
• On the shaded side of the root, auxin accumulates
• Inhibition of cell growth on the shaded side
• Root grows away from the light

Question 18

Are plant roots positively or negatively gravitropic? How does this affect root growth?

Answer 18

Positively gravitropic
Plant roots grow downwards, towards gravity

Question 19

Explain why plant roots are positively gravitropic

Answer 19

• Root placed horizontally
• Due to gravity, auxin accumulates on the lower side of the root
• Inhibition of cell growth on the lower side
• Root bends downwards growing towards gravity

Question 20

Explain how plant tropisms increase the chance of survival

Answer 20

• They enable plants to respond to their environment
• Shoot growth towards the light maximises light absorption
• Root growth downwards increases the uptake of water and minerals from the soil and enables anchorage of the plant body to the ground