Development of Leaf Nitrogen Vertical Distribution in Crop Canopy Research

With the depth of canopy increases,leaf nitrogen content reduces gradually,thus vertical nitrogen gradient develops.Vertical leaf nitrogen distribution is the transference of nitrogen to growing center and an adaptation to the light distribution in canopy.This type of nitrogen distribution increases canopy and single plant photosynthesis rate.On a basis of comprehensively appraising published research,we analyzed several factors which affected the leaf nitrogen vertical distribution in crop canopy;we pointed out the disadvantages of published research and the key problems that ought to be solved and developing perspectives in research of vertical leaf nitrogen distribution in this study.