Plant hormones

Question 1

What is tropism?

Answer 1

A tropism is the response of a plant to a specific stimulus.

Question 2

What is phototropism?

Answer 2

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

Question 3

What is gravitropism?

Answer 3

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

Question 4

What is auxin?

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?

Answer 5

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

Question 6

How do plants shoots show negative gravitropism?

Answer 6

• In a horizontal shoot, auxin accumulates in the lower side due to gravity.
• Cells on the lower side of shoot grow more (more cell elongation), causing the shoot to bend upwards against the direction of gravity.
• As a result, more light is usually available for photosynthesis.

Question 7

How do plant roots show positive gravitropism?

Answer 7

• In a horizontal root, auxin accumulates in the lower side causing cells to grow less (less cell elongation).
• The roots bends in the direction of gravity.
• As a result, more water and nutrients/minerals are available to the plant roots.

Question 8

What are gibberellins?

Answer 8

Gibberellins are a type of plant hormone involved in seed germination.

Question 9

What is ethene?

Answer 9

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