Effect of ammonium concentration on protein and chlorophyll contents and the number of ribosomes in the cells of soybean mixotrophic callus

The effects of exogenous ammonium concentrations on the contents of protein and chlorophyll and also the number of ribosomes in the cells of the mixotrophic callus of soybean (Glycine max L.) were studied. The curves of protein and chlorophyll contents differed at ammonium concentrations exceeded 20 mM. An increase in the content of protein and chlorophyll was observed in the range of ammonium concentrations between 2 and 10 mM. At lower concentrations, their contents were equal to control values. In the absence of ammonium from the nutrient medium, the number of ribosomes in the cells was low. The presence of ammonium in medium (0.01–20.0 mM) induced a manifold increase in the number of ribosomes, which did not depend on the ammonium concentration. It is supposed that ammonium is a factor controlling the formation and functioning of the protein-synthesizing machinery; its indirect effect on the content of the green pigment in chloroplasts of the mixotrophic callus cells is also discussed.