5.4 Plant hormones (Triple)

Question 1

What is a tropism? (Triple)

Answer 1

A tropism is the response of a plant to a certain stimulus

Question 2

What is phototropism? (Triple)

Answer 2

Phototropism is the response of a plant’s shoot or root to light

Question 3

What is gravitropism? (Triple)

Answer 3

Gravitropism is the response of a plant’s shoot or root to gravity

Question 4

What is auxin? (Triple)

Answer 4

Auxin is a hormone which controls the growth of a plant’s shoots and roots. When auxin is unevenly distributed in a growing plant, the rate of growth will also be unequal.

Question 5

How do plant shoots show positive phototropism? (Triple)

Answer 5

1. One side of the shoot is in the light, causing auxin to move to the shaded side
2. At the shaded side, the cells are stimulated to grow - the shoot bends towards the light
3. As a result, photosynthesis can occur at a faster rate

Question 6

How do plant shoots show negative gravitropism? (Triple)

Answer 6

1. In a horizontal shoot, auxin accumulates in the lower side due to gravity
2. Cells on the lower side of the shoot grow more, causing the shoot to bend away from the direction of gravity
3. As a result, more light is available for photosynthesis

Question 7

How do plant roots show positive gravitropism? (Triple)

Answer 7

1. In a horizontal root, auxin accumulates in the lower side, causing cells to grow less
2. The root bends in the direction of gravity
3. As a result, more water and nutrients are available to the plant roots

Question 8

What are gibberellins? (Triple)

Answer 8

Gibberellins are a type of plant hormone involved in seed germination

Question 9

What is ethene? (Triple)

Answer 9

Ethene is a type of plant hormone involved in cell division and ripening

Question 10

What are the uses of auxins? (Triple)

Answer 10

● Weedkillers: auxin
causes cells to
grow at a rapid
rate, causing plant
death

● Rooting powder:
auxin causes new
plant to grow very
quickly

● Tissue culture:
auxin promotes
growth of roots
and shoots

Question 11

What are the uses of ethene? (Triple)

Answer 11

Control of food ripening in the food industry - allows fruit to be ripened just before they are sold

Question 12

What are the uses of gibberellins? (Triple)

Answer 12

● Termination of seed dormancy

● Promotion of seed flowering

● Increase of fruit size