Shade Avoidance

Question 1

What morphological changes does shade tolerance cause?

Answer 1

• Internodes elongate
• Longer petioles
• Smaller leaves

Question 2

How do seeds, seedlings and mature plants exhibit shade avoidance?

Answer 2

Seeds: don’t germinate
Seedlings: etiolate
Mature plants: change form, morphological.

Question 3

How is an Arabidopsis seedling emerging in vegetative shade different to one emerging in direct light?

Answer 3

Direct light: Seedling will de-etiolate

Vegetative shade: Seedling will de-etiolate and be shade tolerant due to HIR and PhyA being destroyed after a period of illumination. Then the seedling will etiolate and become shade avoider.

Question 4

What are photoconversion rates in Arabidopsis?

Answer 4

Photoconversion rates are similar for phytochromes
PhyB reverts faster in darkness. This tells the plant how long nights are and is important for flowering.

Question 5

What are photoconversion rates in potato and maize?

Answer 5

PhyB and PhyE revert, PhyA and PhyC do not revert.

Question 6

What light stimulates shade avoidance?

Answer 6

End of day far-red light stimulates shade avoidance.

Question 7

What happens when far-red light is reflected off of neighbouring plants, or travels through leaves from above?

Answer 7

Stimulates shade tolerance, competition.

Question 8

Why is shade avoidance important commercially?

Answer 8

Plants not actually shaded, but having R:FR ~1 will trigger shade avoidance due to the reflected far-red light.
Causes lower yield.