Short-term shifts in nitrogen metabolism in mulberry Morus alba under salt shock

Abstract

Important biochemical parameters of nitrogen metabolism were studied in the leaves and roots of mulberry, Morus alba, subjected to NACl salinity. The total protein content of the shocked plants declined with a progressive increase in accumulation of free amino acids. Concurrently, the protease activity in the tissues was also increased. Nitrate reductase (NR) activity declined under stress conditions. Ammonia was accumulated significantly in the tissue under salt stress conditions. The enhanced activities of NADH- and NADPH-dependent glutamate dehydrogenase (NADH- and NADPH-GDH) coupled with increased activities of aspartate aminotransferase (AAT) and alanine aminotransferase (AlAT) may be involved in detoxifying the excess levels of ammonia (by assimilation) found under stress conditions. The increased activity of glutamine synthetase (GS) during stress conditions paralleled the elevated levels of glutamine in the tissue. The magnitude of these changes increases over time and with stress intensity.bl]