Comparison of Photosynthetic and Photorespiratory Enzyme Activities between Green Leaves and Colorless Parts of Variegated Leaves of a C_4 Plant, Stenotaphrum secundatum (Walt.) Kuntze

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The activities of enzymes involved in C_4 photosynthesis and photorespiration in colorless parts of variegated leaves of Stenotaphrum secundatum (Walt.) Kuntze were compared with those in green leaves. Chlorophyll content of the colorless part was only about 0.3-3% of that of the green leaves. The activities of chloroplastic enzymes, pyruvate, P_i dikinase, NADP^+-malic enzyme and NADP^+-glyceraldehyde 3-phosphate dehydrogenase were considerably lower in colorless tissue on a fresh weight or protein basis (the ratios of the activities in the green/colorless tissues ranging from 5 to 20). A cytoplasmic enzyme, UDP-glucose pyro-phosphorylase as well as aspartate and alanine aminotransferases showed comparable activities in the two types of tissue, whereas PEP carboxylase in the colorless tissue had only the one-third activity of that in green tissue. Differences in activities were also observed for the glycolate pathway enzymes (the ratios ranging from 2 to 7 for glycolate oxidase, hydroxypyruvate reductase and serine hydroxymethyltransferase, and 7 to 15 for catalase), while cytochrome c oxidase showed comparable activity in the two types of tissue. The results suggest that the deficiency of thylakoid development in the colorless tissue influences enzyme activities not only in plastids but also in other cellular compartments.
日本植物生理学会の論文