Photosynthesis In Elodea canadensis Michx

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Abstract
Experiments to determine the early labeled photosynthetic products in Elodea canadensis show that after 2 seconds of exposure to NaH14CO3, 45% of the 14C incorporated is located in malate and aspartate. Phosphoglyceric acid and sugars account for 27% of the label during similar exposures. Equivalent amounts of organic acids and C3 cycle products are present after 8 seconds. Four-carbon acids remain relatively unchanged throughout the first 45 seconds of exposure, while sugars increase in a linear fashion. Enzyme assays indicate that ribulose diphosphate and phosphoenolpyruvate carboxylase enzymes are present in a ratio of approximately 2:1. It appears that E. canadensis is able to synthesize significant amounts of four-carbon acids via β-carboxylation and this may play a role in maintaining a pH favorable for carboxylation in aquatic plants.