Assimilation of carbon dioxide in mesophyll chloroplasts and bundle sheath strands mechanically isolated from corn leaves

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Mesophyll chloroplasts capable of assimilating 1.2μmoles CO_2 per milligram chlorophyll per hour were isolated from 7-day-old corn (Zea mays, Nagano No. 1 ) leaves. Addition of phosphoenolpyruvate increased the rate of CO_2 fixation in light. up to 22 μmoles per milligram chlorophyll per hour, while exogenously added ribose 5-phosphate and adenosine triphosphate brought about only small increases. The CO_2 fixation products were mostly malate and aspartate. Bundle sheath strands isolated from the same plants were capable of assimilating 3-26 μmoles CO_2 per milligram chlorophyll per hour. The fixation rate increased 3- to 5-fold on addition of ribose 5-phosphate and adenosine triphosphate, while exo-genous phosphoenolpyruvate had no effect. The bulk of early products of light-induced CO_2 fixation were phosphate esters. These results indicate that corn mesophyll chloroplasts initially fix CO_2 by phos-phoenolpyruvate carboxylase and that reductive pentose phosphate cycle occurs in corn bundle sheath cells, but not in the mesophyll chloroplasts.
日本植物生理学会の論文