Effect of nitrogenous fertilizer levels on photosynthetic functions of maize ear leaves at grain filling stage

On the basis of a long-term experiment in brown soil, the photosynthetic characteristics of maize (cultivar, Zhengdan 958) ear leaves at the filling stage, SPAD value, gas exchange and chlorophyll fluorescence parameters were measured under different levels of nitrogen treatments. The results show that the OJIP Fluorescence induction curve is affected significantly by nitrogen fertilization, and the fluorescence intensity of K, J and I steps are significantly decreased. The probability that a trapped exciton moves an electron into the electron transport chain beyond QA (o) and the performance index on absorption basis (PIABS) are significantly increased under the nitrogen fertilization, while the relative variable fluorescence intensity at the K-step (Wk) and the relative variable fluorescence intensity at the J-step (Vj) are significantly reduced. It is shown that the comprehensive performance of electron transport chain in PSⅡ reaction center as well as the electron transport capacity both in the donor side and the receptor side are improved obviously. The performance of the receptor side is greater than that of the donor side. With nitrogen fertilizer levels increasing, the maximal oxidationreduction activity of PSⅠ(I/Io) is increased first and then decreased, which indicates a moderate amount of nitrogen fertilizer could enhance the maximal oxidationreduction ability of P700, and could significantly improve coordination between PS I and PSⅡ optical systems Ф(PSⅠ/PSⅡ) in maize leaves.