GLUTAMATE SUPPLEMENTATION ALLEVIATES THE OXIDATIVE EFFECTS OF SALINITY ON GROWTH AND CHLOROPHYLL SYNTHESIS IN VIGNA RADIATA BY UP-REGULATING TOLERANCE MECHANISMS

Influence of the exogenously applied glutamate (0, 0.5, 1, 2 and 5 mM) was investigated on growth, chlorophyll synthesis and some tolerance mechanisms in Vigna radiata grown on salt stress. Salt stress (100 mM NaCl) reduced height, fresh and dry weight of shoot while as glutamate supplementation mitigated the decline. Applied glutamate affectively increased glutamate 1-semialdehyde, δ-amino levulinic acid and the activity of δ-amino levulinic acid dehydratase, and in addition assuaged the decline caused by salt stress. Treatment of glutamate alleviated the decline in total chlorophyll, carotenoids and the activity of rubisco with highest increase imparted due to 1 and 2 mM glutamate. Activity of chlorophyllase increased due to salt stress and glutamate treated plants exhibited a decline in its activity. The activity of nitrate reductase and glutamate synthase was reduced due to salt stress and glutamate supplementation mitigated the decline and also increased their activities in unstressed conditions. Content of proline and sugars increased due to the supplementation of glutamate in both unstressed and salt stressed plants. The activities of antioxidant enzymes (SOD, POD, APX and CAT) and the content of reduced glutathione and tocopherol increased due to glutamate treatments. Salinity triggered enhancement in hydrogen peroxide and the lipid peroxidation was mitigated by the exogenous treatment of glutamate. Nitrogen and potassium content was reduced while as sodium and chloride accumulation increased due to salt stress, however treatment of glutamate mitigated the decline in nitrogen and potassium and also reduced the accumulation of sodium and chloride. Hence, glutamate treatment can be exploited to prevent the adverse effects of salinity on Vigna radiata growth and metabolism.