Abstract
In soyabeans (Glycine max (L.) Merr.), glutamine synthetase (GS) activity was greater at 28 °C than at 35 °C. The reverse was true for foliar-N loss. In field-grown plants at 29 °C, the GS activity was higher and foliar-N loss was lower in soyabeans than in Amaranthus palmeri (S.) Wats. Methionine sulphoximine, a GS inhibitor, and 6-diazo-5-oxo-L-norleucine, a glutamate synthase inhibitor, significantly increased foliar-N loss from soyabeans. The data suggest that conditions conducive to decreased GS or glutamate synthase activity may result in increased foliar-N loss.