Effect of sulfate supply level on characteristics of N and S metabolism and on root vigor of corn
硫水平对玉米氮、硫代谢特性及根系活性的影响

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 relatioinship between protein content and NR activity in S deficiency.Deficient or excessive S supply limited N and S metabolism of corn plant.N/S or inorganic S/total S ratio in roots was a sensitive index to indicate the deficiency of S supply,which was 10.7 or 0.302 under normal condition,respectively.