Modifying Carbon Assimilation

In algae grown phototrophically, all new biomass - including lipids - derives from the fixation of CO2 into ribulose-l,5-biphosphate (RuBP) to form 3-phosphoglycerate, catalyzed by the enzyme ribulose-l,5-biphosphate carboxy-lase/oxygenase (RuBisCO). Several other enzymes are also required to regenerate RuBP in the Calvin cycle. Considerable amounts of ATP and NADPH are required 

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Fig.2.6 Overall design of photosynthesis. The light reactions make ATP and NADPH to be used in the carbon dioxide assimilation reactions that form fructose and glucose (Modified from Fig. 19-37 in Lehninger Principles of Biochemistry. D.L. Nelson M.M. Cox, 4th Ed. 2005. W.H. Freeman Co., New York)...

CO2 flux and H2O flux pass through stomata. Stomatal aperture depends on both internal and external factors. As Wong et a/., 1979, pointed out, the capacity of the mesophyll tissue to fix carbon allows the regulation of stomatal conductance (gc) For instance, DCMU, an inhibitor of photosynthetic electron transport, modifies both mesophyll CO2 assimilation and stomatal conductance in such a way that the intercellular concentration of CO2 (Ci) remains proportional to the air CO2 concentration (Ca) ... 

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