A suspension culture of soybean (Glycine max L.) was
grown on a defined medium in whichi the nitrogen sources
were nitrate (25 mM) and ammonium (2 mM). The cells did
not grow on nitrate unless the medium was supplemented
with ammonium or glutamine. The L- and D-isomers of 12
amino acids tested singly could not replace ammonium.
-Most amino acids (4 mM) inhibited growth when the cells
were cultured on nitrate and ammonium. Cells from five
other plants (Reseda luteoli L.; Triticum monococcum L.;
flax, Linum usitatissimum L.; horseradish, ,4moracia lapathifolia
Gilib; Haplopappus gracilis L.) grew on the defined
mediuni with nitrate (25 mM) as the sole nitrogen source.
Higher cell yields were obtained when ammonium (2 mM)
or glutamine also was present. Supplementing the defined
medium with high concentrations of ammonium (20 mM)
inhibited growth of soybean, Haplopappus, and wheat cells.
Addition of citrate (5 mM) relieved the inhibitory effects of
ammonium in soybean and wlheat cells but not in the Haplopappus
cells.