A correlative analysis of oxalate degradation and early nitrate assimilation in grain sorghum grown under sodium chloride stress

Seedlings of grain sorghum (Sorghum vulgare Var. CSH-14) were grown upto 10 days in Hoagland's solution with different levels of NaCl (0, 20, 50 and 100 mM). The changes in oxalate degradation through oxalate oxidase (OXO) and the activities of enzymes of nitrate assimilation pathway, viz. nitrate reductase (NR) and nitrite reductase (NiR) were examined in leaves. The activity of oxalate oxidase correlated statistically with the activities of the enzymes of nitrate assimilation suggesting thereby a possible link between oxalate oxidation and nitrate assimilation. The degradation of oxalate by oxalate oxidase increased with increasing level of NaCl upto 50 mM concentration with increasing production of H₂O₂ in leaves. Activities of nitrate reductase and nitrite reductase were suppressed by NaCl salinity, showing a significant negative correlation with oxalate degradation. This shows that oxalate degradation and nitrate assimilation in grain sorghum are simultaneously affected by salt stress.