1. Limiting Factors in Photosynthesis
Song Hee Bae
IB1 Biology

2. The Concept of Limiting Factors
Light intensity
Carbon dioxide concentration
Temperature
Changing the limiting factor increases or decreases the rate

3. The Effect of Light Intensity
Not usually the limiting factor
At low light intensities, shortage of NADPH and ATP
Rate-limiting where Glycerate 3-phosphate is reduced

4. The Effect of CO₂ Concentration
At low and medium CO₂
Rate-limiting where CO₂ is fixed to produce glycerate 3-phosphate
Level of CO₂ is never very high
Often the limiting factor

5. The Effect of Temperature
At low temperature, enzymes work slowly
At high temperature, RuBP ineffective
Rate-limiting where CO₂ is fixed

6. Temperature
CO₂ Concentration
Light intensity

7. Results of Limiting Factors

8. Cyclic Photophosphorylation
When light is not limiting factor
NADPH accumulation, NADP+ shortage
Normal flow of electrons inhibited
Alternative route is cyclic photophosphorylation
See page 81

9. Vocabulary Reference Limiting factor Cyclic photophosphorylation
Study guide page 81