Effect of sulfate supply level on characteristics of N and S metabolism and on root vigor of corn

The effects of different sulfate supply level on N and S metabolism and on root vigor of corn were quantitatively studied with Hoagland solution under greenhouse conditions. The results showed that in S-deficient solution, root vigor and leaf nitrate reductase (NR) activity significantly rdduced, top root ratio (T/R) increased, and S and N accumulation in tops and roots decreased. The partition of S decreased in roots and incompletely expanded leaves, but increased in senescent leaves and sheaths-stems; while the partition of N increased in roots, but decreased in incompletely and fully expanded leaves. The content of protein, protein N, protein S, and sulfate S significantly reduced, percentage of non-protein N increased, inorganic S/total S ratio decreased, and total N/total S ratio increased. The protein N/protein S ratio in tops had no observable changes, but increased significantly in roots, showing that root was a sensitive organ to S-deficiency. There was a close relationship between protein content an