Limiting Factors (photosynthesis)

Question 0

What does it mean when the light intensity graph is increasing?

Answer 0

• light intensity is limiting

* increasing light intensity increases the rate of photosynthesis

Question 1

What factors limit photosynthesis?

Answer 1

• light intensity - limits light dependent stage
- limits photophosphorylation
- limits photolysis of water
• CO2 availability
• temperature

Question 2

What does it mean when the light intensity graph plateaus?

Answer 2

• light intensity is not limiting, CO2 conc or temp is

* increasing light intensity has no effect on rate of photosynthesis

Question 3

What does it mean when the CO2 availability graph is increasing?

Answer 3

• CO2 is limiting

* as the concentration of CO2 increases so does the rate of photosynthesis

Question 4

What does it mean when the CO2 availability graph plateaus?

Answer 4

• CO2 is not limiting

* decreasing the concentration of CO2 has no effect on the rate of photosynthesis

Question 5

What happens to the rate of photosynthesis when the temperature is under 25 degrees?

Answer 5

• the photosynthesis rate approximately doubles every 10 degrees rise in temp
• photosynthesis is at a higher rate than photorespiration

Question 6

What happens to the rate of photosynthesis when the temperature is over 25 degrees?

Answer 6

• enzymes work less efficiently
• oxygen competes more successfully for the active site of rubisco and prevents it from accepting CO2 (photorespiration).
• photorespiration is at a higher rate than photosynthesis

Question 7

What happens to the rate of photosynthesis when the temperature is over 40 degrees

Answer 7

• enzymes denature

* little or no photosynthesis