Regulation of photosynthetic carbon flow by ammonium ions in isolated bean leaf cells

Isolated leaf cells of bean, Dolichos lablab photosynthesised more of amino acids at the expense of sugars, when they were incubated with 1mM ammonium hydroxide. This concentration of ammonium did not inhibit the total incorporation of CO2 into the cells. The studies on oxygen exchange reactions, 14C-leucine incorporation, levels of photosynthetic carbon flowing into lipids, nucleic acids and insoluble fractions of the cells, specific enzyme activities of glutamate dehydrogenase, glutamine synthetase, pyruvate kinase, fructose 1, 6-diphosphatase, malate dehydrogenase, and α-oxoglutaric semialdehyde dehydrogenase - all showed no appreciable difference between the control and ammonium-treated cells. The enzymatic mechanism for such a preferential flow of photosynthetic carbon into amino acids is obscure. (auth.)