DYNAMICS OF DISTRIBUTION OF C-14-LABELED PHOTOSYNTHETIC PRODUCTS DURING EXPOSURE OF PEA LEAF PROTOPLASTS UNDER LIGHT AND IN THE DARK

Protoplasts from pea leaves (Pisum sativum L.) were exposed to photosy nthesis-saturating light in the presence of 1 mM (NaHCO3)-C-14 for a p eriod of 10 min at 20-degrees-C. The C-14 isotope was then washed away and exposure of the protoplasts continued in the presence of 1 mM (Na HCO3)-C-12 in the dark or under light. In the dark, the content of C-1 4 declined in sugars and phosphorylated compounds, while increasing at the same time in organic acids of the tricarboxyhc acid cycle (TAC). Saturation of the pools of succiuic, fumaric, and 2-oxoglutaric acids was observed after 4 h of residence in the dark, whereas accumulation of C-14 in malic and citric acids continued for a period of 20 h. Unde r light, the radioactivity of sugars remained at a constant level, whi le content of the label in phosphorylated compounds declined for a per iod of 2 h at an increase of 14C content in organic acids. The rate of label accumulation in individual acids of the TAC was significantly l ower under light than in the dark. The inhibitor of succinate dehydrog enase malonate (10 mM) caused an increase of label content in succinat e both in the dark and under light, although to a lesser extent in the latter case. Radioactivity of the amino acid fraction declined weakly , doing so more rapidly under light than in the dark. The possibility of functioning of the tricarboxylic acid under light is discussed in t he paper.