The Effects of Nitrogen Level on the Root and Shoot Growth and Their Relationship with the Water Use Efficiency in Wheat Plants

A solution cultured simulating experiment had been conducted to study the effects of nitrogen application on the root and shoot growth and water use efficiency of two different drought-resistance spring wheat.The results showed that nitrogen application could increase leaf photosynthetic rate(Pn),transpiration rate(Tr),stoma conductance(Gs),water use efficiency(WUE),and promote the shoot and root growth,but the ratio of root to shoot(R/S) decreased as the nitrogen level increased significantly.Root volume,root bulk density and root water content increased firstly and decreased finally as the nitrogen level increased.It was indicated that the root water content was highest when Root/shoot ratio was about 0.3 in this experimental,but the higher or lower R/S was not favor to the WUE increasing.the Pn,Tr and Gs was increased with the root water content increasing,but the increscent extent of Pn was higher than Tr,so the leaf WUE increased continuously as the root water content increased.Under the rate nitrogen application,the R/S,root volume and root dry matter of dryland cultivar was higher than waterland cultivar,and reasonable nitrogen application can promote root development and harmonize the root and shoot growth,therefore,the drought-resistance capability and higher WUE in wheat plants could be obtained synchronously.