Plant Responses

Question 1

Effect of auxins

Answer 1

• cell elongation
• shoot growth
• inhibit growth of side shoots
• inhibit leaf abscissions
• promote growth in cambium

Question 2

Describe phototropism

Answer 2

Auxin made in shoot tip
It moves to the opposite side to where light is
Cells grow more on this side (cell elongation)
Which pushes the end of the shoot towards the light

Question 3

Example of negative geotropism

Answer 3

Shoot (growth)

Question 4

Explain positive geotropism and auxin in roots

Answer 4

Auxin inhibits cell elongation on the upper side
Auxin accumulates on the lower side
Lowe side grows more so root bends downwards

Question 6

Auxin & ABA: controlling plant growth

Answer 6

High apical auxin keeps abscisic acid levels high too, this maintains apical dominance and inhibits lateral shoot growth. Cytokinins accumulate in the shoot tip

Question 7

Gibberellin: Seed Germination

Answer 7

Seed absorbs water, embryo releases gibberllin
Gibberellin travels to aleurone layer and stimulates the production of amylase
Amylase breaks down starch to glucose
Increased respiration, increased ATP
More growth and protein synthesis

Question 8

Stomatal closure

Answer 8

ABA binds to receptors on guard cells
K leaves the cell, this increases water potential inside tech cell
So water leaves by osmosis and cell becomes flaccid, closing stomata

Question 9

Leaf loss

Answer 9

Auxin inhibit leaf abscission
Falling temperatures and light levels decrease auxin levels
More ethene is produced as leaves get older
Abscission layer sensitive to ethene stimulates enzymes that weaken cell wall a causing the leaf to fall