Studies On Roots And Nutrient Accumulation Of Maize Varieties Released In Different Years Under Low Nitrogen And Drought Stresses

The effect of low nitrogen and drought stresses on root characteristic, leaf stay-green and NPK accumulation were studied, using maize varieties released since 1970 s that have been promoted widely and a new variety, under normal water and nitrogen, low nitrogen(LN) and combined stress of low nitrogen and drought(LD). The results showed that:1. In the process of time, root dry weight, root length and root surface area of the varieties in different years increased at first and then decreased, finally increased again. Root bleeding sap of the varieties increased gradually. Low nitrogen and drought stresses affected root morphology and physiological activity. Root weight, root length and root surface area increased, and root bleeding sap decreased under LN, root weight decreased significantly under LD. Compared with the old varieties, root dry weight of the modern varieties changed smaller, root length and surface areas increased more, root average diameter became thinner, root bleeding sap decreased non-significantly under the LN and LD conditions. In the process of time, root morphology of the varieties have been optimized gradually, root physiological activity have been increased, and the LN and LD stress tolerance in modern varieties have been increased. These changes would ensure relatively sufficient nutrient and water for yield improvement.2. The more modern maize varieties had better leaf stay-green traits and higher SPAD reading of ear leaves than the older varieties. Leaf stay-green traits and SPAD reading of ear leaves decreased under low nitrogen and drought stresses, the more modern maize varieties fell less than the older ones. The more modern maize had better leaf stay-green traits and slower leaf senescence in later growth period, which were less affected by low nitrogen and drought stresses.3. In the process of time, nitrogen accumulation in kernels and shoot, nitrogen content in kernels, nitrogen partial factor productivity and nitrogen recovery efficiency of the varieties in different years increased gradually, but nitrogen agronomic efficiency decreased. Nitrogen(N), phosphorus(p) and potassium(K) accumulation in every organ of plants decreased under low nitrogen and drought stresses, NPK content in every organ of plants also were affected by these stresses. NPK content in every organ of plants decreased under LN. NK content in roots decreased, P content in roots increased, NPK content in straw decreased, NPK content in kernels increased under LD. NPK accumulation in shoot and root of the more modern maize varieties fell less than the older ones under LN, there was no significant difference in shoot under LD, but NP accumulation in root of the more modern ones fell less than the older ones under LD. The more modern maize varieties could uptake and utilize more nitrogen, accumulate more nutrient, product more grain yield, and the LN and LD stress tolerance in the more modern varieties have been increased.