Limiting Factors in Photosynthesis Song Hee Bae IB1 Biology

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

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

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

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

Temperature CO₂ Concentration Light intensity

Results of Limiting Factors

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

Vocabulary Reference Limiting factor Cyclic photophosphorylation Study guide page 81