A VIRESCENS MUTANT OF PHASEOLUS VULGARIS: PHOTOSYNTHESIS AND METABOLIC CHANGES DURING LEAF DEVELOPMENT

Abstract

SummaryFixation of 14CO2, photophosphorylation, and protein, lipid and RNA composition have been compared for primary and trifoliate leaves of various ages of control and mutant plants.Except when old, leaves of control plants fix more CO2 than do those of the mutant, but the carboxylation pathways seem similar in the two plants. The level of Fraction I protein and that of ribulose diphosphate carboxylase activity are also similar, but lower in leaves of the mutant. Photophosphorylation per chloroplast mediated by photosystems I and II, tends to be slightly higher in the mutant, despite lower levels of chlorophyll in mutant plastids. Small differences in amount and composition of leaf lipids, but large differences in RNA content were found. Mutant leaves show a higher initial content of cytoplasmic ribosomal RNA than do controls; as leaves age this position is reversed. Chloroplast ribosomal RNA is initially similar, but continued synthesis is greater and more prolonged in the mutant.The significance of these data is discussed in relation to the nature of the mutation.