Chapter 16: Plant Responses

Question 1

Define tropism.

Answer 1

• Directional growth of a plant in response to environmental cues such as light or gravity.

Question 2

Outline the roles of auxins in plants.

Answer 2

• Control cell elongation.
• Prevent leaf fall (abscission).
• Maintain apical dominance.
• Involved in tropisms.
• Stimulate ethene release.
• Involved in fruit ripening.

Question 3

Outline the roles of gibberellin in plants.

Answer 3

• Stem elongation.
• Mobilisation of food stores in a seed at germination.
• Stimulate pollen tube growth at fertilisation.

Question 4

Outline roles of ethene in plants.

Answer 4

• Fruit ripening.

- Promote abscission in deciduous trees.

Question 5

Outline role of ABA (abscisic acid) in plants.

Answer 5

• Maintains dormancy of seeds + buds.
• Stimulates cold protective responses –> antifreeze production.
• Stimulates stomatal closing.

Question 6

Outline process of using plant hormones in germination.

Answer 6

1.