Growth and Development of Soybean (Glycine max [L.] Merr.) Pods: CO2 Exchange and Enzyme Studies 1

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RESUMO

The rates of CO2 exchange and 14CO2 incorporation in the light and dark and the activities of several photosynthetic, photorespiratory, and respiratory enzymes of soybean (Glycine max [L.] Merr. cv. Wye) reproductive structures were determined at weekly intervals from anthesis to pod maturity. At all stages of pod development soybean reproductive structures were found to be incapable of net photosynthesis under the experimental conditions employed, but capable of gross photosynthesis and light-induced 14CO2 uptake. Consistent with the lack of net photosynthesis throughout the development of the reproductive structure, the maximum in vitro activity of ribulose 1,5-bisphosphate carboxylase (EC 4.1.1.39) in pod tissue was only 3% of that in leaf extracts when expressed on a fresh weight basis. We concluded that the major role of the reproductive structure of the soybean with respect to photosynthetic carbon metabolism is the reassimilation of its respiratory CO2.

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