Extracts of Mesophyll and Bundle Sheath
نویسنده
چکیده
The activities of certain enzymes related to the carbon assimilation pathway in whole leaves, mesophyll cell extracts, and bundle sheath extracts of the C4 plant Panicum miliaceumn have been measured and compared on a chlorophyll basis. Enzymes of the Co dicarboxylic acid pathway-phosphoenolpyruvate carboxylase and NADP-malic dehydrogenase-were localized in mesophyll cells. Carbonic anhydrase was also localized in mesophyll cell extracts. Ribose 5-phosphate isomerase, ribulose 5-phosphate kinase, and ribulose diphosphate carboxylase enzymes of the reductive pentose phosphate pathway-were predominantly localized in bundle sheath extracts. High activities of aspartate and alanine transaminases and glyceraldehyde-3-P dehydrogenase were found about equally distributed between the photosynthetic cell types. P. miliaceum had low malic enzyme activity in both mesophyll and bundle sheath
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Low bundle sheath carbonic anhydrase is apparently essential for effective c(4) pathway operation.
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