Effect of Nitrogen and Sulphur Application on Nitrate Reductase and ATP- sulphurylase Activities in Soybean

摘要

A number of field experiments were conducted to assess the role of combined application of nitrogen and sulfur to increase the seed and oil yield of non-nodulating soybean (Glycine max (L) Merr.) cv. PK-416 (V_1 and cv. PK-1024 (V_2). Six combinationsof N and S in three replicates each were used for this purpose i.e. 0 S + 23.5 kg Nha ~(-1) (TO; 0 S + 23.5+20 kg N ha~(-1) (T_2); 40 S + 23.5 kg N ha~(-1) (T_3); 40 S + 23.5 + 20 kg N ha~(-1)); 20+20 S + 23.5 kg N ha~(-1) (T_5); 20+20 S + 23.5+20 kg Nha~(-1) (T_6). Nitrate reductase (NR) and ATP-sulphurylase activities in the leaves were measured at various growth stages as the two enzymes catalyze the rate limiting steps of the assimi-latory pathways of nitrate and sulphate, respectively. The activities of these enzymes were strongly correlated with seed yield. The higher seed, oil and protein yields were achieved with the treatment T_6 in both the cultivars due to optimization of NR activity and ATP-sulphurylase activity, as these parameters wereinfluenced by N and S assimilation. Any variation from this combination was observed to decrease the activity of these enzymes resulting in reductions in the seed, oil and protein yield of soybean.