[Light and nitrate utilization by soybean callus cells]

We studied the role of light during exogenous assimilation of nitrate (as the only source of nitrogen) by the callus cells of soybean (Glycine max). The nitrate absorbed and assimilated by the photosynthetic (mixotrophic) and non-photosynthetic cells (heterotrophic and chlorophyll-containing cells cultivated in the light in the same medium with diuron) was quantified. The assimilated nitrate was quantified at the final stage of the growth cycle as the difference between the amount of nitrogen absorbed from the medium and the amount of endogenous nitrate in the cells. Comparison of the assimilated nitrate quantities per accumulated dry biomass between the photosynthetic and non-photosynthetic cells demonstrated that nearly 30% of nitrate is assimilated with the help of photosynthesis in a mixotrophic culture when nitrate is the only source of nitrogen.