Plant responses

Question 1

Explain what is meant by a tropism

Answer 1

Growth of a plant is in a direction determined by a stimulus

(phototropism, geotropism, thigmotropism etc.

Question 2

State one example of a receptor in a flowering plant

Answer 2

Photoreceptor molecules in the coleoptile region

Question 3

State one example of an effector in a flowering plant

Answer 3

The region of cell elongation (Cells in the shaded side elongate more than on the illuminated side)

Question 4

What is abiotic stress?

Answer 4

Environmental factors that could harm a plant e.g drought, mineral deficiency

Question 5

How do plants respond to abiotic stress and herbivory

Answer 5

Antifreeze enzymes
Bitter tasting tannins
Contain nitrogenous compounds like alkaloids
Cell signalling pheromones to trigger defence mechanisms

Question 6

How is leaf abscission in deciduous plants controlled?

Answer 6

Abscisic acid (ABA) stimulates ethene production

Triggers production of cellulase enzymes which breaks down cell wall of abscission layer

Leaves break from branch. Protective layer forms (suberin) to stop entry of pathogens and vascular tissue sealed.

Question 7

Function of gibberelin?

Answer 7

Stimulates germination

Stimulates cell elongation at internodes

Fruit growth