MODULE 5: Plant Responses !!

Question 1

The role of auxins in apical dominance:

Answer 1

• effect on cell wall plasticity
• effect on lateral growth
• effect on root growth

Question 2

Auxins effect on cell wall plasticity:

Answer 2

• Auxin binds to receptors in the plasma membrane
• Causes pH to drop to 5
• Optimum for enzymes to maintain cell wall plasticity
• Cells mature, auxins destroyed
• pH increases, rigidity increases
• Inhibits growth

Question 3

Auxins effect on lateral growth:

Answer 3

• Auxins grow in the tip of shoots
• As the shoot grows, the concentration of auxins decreases down the shoot
• This causes slower/less lateral growth
• Apical dominance

Question 4

Auxins effect on root growth:

Answer 4

• High concentrations of auxins inhibits root growth

- Low concentrations of auxins increases root growth

Question 5

Experiment to investigate auxins effect on cell wall plasticity:

Answer 5

Changing the concentration of IAA and measuring pH and cell elongation over time

Question 6

Experiment to investigate auxins effect on lateral growth:

Answer 6

Removing the apical tip that contains auxin-producing cells, so less cell elongation occurs and more lateral growth can occur. If auxins are applied artificially, apical dominance will resume

Question 7

Experiment to investigate auxins effect on root growth:

Answer 7

Remove of apical tip that contains auxin-producing cells, so less auxins reach the roots which slows/stops root growth. Auxins can be added to the tip of the shoot artificially, which can be used to measure the optimum concentration for root growth