Limiting Factors in Photosynthesis

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

• Limiting factor
• Cyclic photophosphorylation

Reference

• Study guide page 81