Behaviour of nodulatedPisum sativum L. under short-term nitrate stress conditions

Abstract

Nitrate (20 mM) applied to the root medium of 28-day-old nodulated pea plants (Pisum sativum L., cv. Jupiter) immediately retarded nodule growth and inhibited root nodulation. Acetylene-reducing and H2-evolving nitrogenase activities were also significantly inhibited. The inhibitory effect of nitrate on nodule respiration was less pronounced while the respiration of roots was increased after the addition of nitrate. The levels of cytosol glutamine synthetase and nitrate reductase in nodule cytosol were permanently decreased from the 4th day after nitrate application. These results indicate that the inhibitory effect of high nitrate concentration on whole nodule metabolism is nonspecific in nature.