Light Damage & Protection

Question 0

Plant protection against light damage: (4)

Answer 0

Reduction of light interception.
Production of protective molecules.
CO2 concentration.
Photo respiration.

Question 1

Light damage threats to plants: (4)

Answer 1

Free radicals.
Photo oxidation.
Sun flecks.
Photo inhibition.

Question 2

Damage by photo inhibition: (2)

Answer 2

Over exciting of photosynthetic system.

Causes a reverse block of PS.

Question 3

Damage by photo oxidation: (2)

Answer 3

By free radicals - serious, irreversible damage.

Causes bleaching of leaves.

Question 4

Damage by free radicals: (1)

Answer 4

The formation of highly dangerous forms of oxygen.

Question 5

Damage by sun flecks: (4)

Answer 5

Light penetrates gaps in the canopy.
Wind causes them to move quickly.
Unfiltered light.
Can cause a ten fold increase in light flux.

Question 6

Protection by reduction of light molecules: (2)

Shiny leaves

Answer 6

Protect by a thick shiny layer of wax; reflects a proportion of incident light and reduces water loss.

Not used by shaded plants.

Question 7

Protection by the production of protective molecules: (2)

Sacrificial molecules

Answer 7

Made with the purpose of being destroyed.

Plants produces special pigments - carotenoids, which readily react with free radicals.

Question 8

Protection by CO2 concentration: (4)

Answer 8

Very energy demanding - only an option when excess light energy is available.
Used by C4 plants.
Used by tropical plants.
CO2 is concentrated in PS cells to ensure a constant supply.

Question 9

Protection by photo respiration: (3)

Answer 9

Used by C3 plants.
Uses high energy molecules; converted back to sugars in dark reactions.
Releases CO2 from sugars to create an internal supply for the plant.