The comparative study on fitting light response curve model of photosynthesis of maize under different nitrogen fertilizer levels

【Objectives】 In this paper, seven different light response models were used to optimize the best model under nitrogen stress through comparing the advantages and disadvantages of different fitting models. This study could provide a scientific basis for the research of nitrogen nutrition physiology and cultivation of corn, and a theoretical basis for the N efficient management of spring corn in brown soil region. 【Methods】 On basis of a long-term experiment in brown soil, the photosynthesis of a maize (cultivar, Zhengdan958) ear leaves at the filling stage was measured under different levels of nitrogen treatments, and seven different light response models, including quadratic regression model, rectangular hyperbola model, non-rectangular hyperbola model, rectangular hyperbola modified model etc., were used to selected the best model by comparing the fitting degree and the five parameters, apparent quantum efficiency (α), maximum net photosynthetic rate (Pnmax), light saturation point (LSP), light compensation point (LCP) and dark respiration rate (Rday).【Results】 1) With the increase of the nitrogen level, the yield, nitrogen content and chlorophyll content of corn are increased, while the net photosynthetic rate of the nitrogen treatments shows a reduced tendency. 2) In this study, the seven kinds of the models can be well applied to fitting the corn leaf Pn light response of high amount nitrogen fertilizer treatment N180, the determination coefficient of the rectangular hyperbola correction model is 0.992, and the determination coefficients of the other models are 0.994. The fitted photo inhibition phenomena of the N0 and N120 treatments are different, so the different models extend to handle different fitting effects, the decision coefficients are in order: The rectangular hyperbola modified model and the quadratic regression model the non-rectangular hyperbola model the exponential model the rectangular hyperbola model and the dynamic model. 3) The photosynthetic parameters of Pnmax, LSP, LCP and Rday of the right angle hyperbolic correction model and quadratic regression model are close to the measured values, and the other models in addition to the individual parameter are relatively close to, and most of the parameters vary obvious. Because the right Angle hyperbolic model, the right Angle hyperbolic model and the dynamic model have not extrema, light saturation point could not get directly, and LSP values of these three models have been lost. 4) With the increase of the nitrogen level, the five parameters, α, Pnmax, LSP, LCP and Rday, are all increased.【Conclusions】With the increase of the nitrogen level, the photosynthetic performance of corn leaves at the filling stage are improved significantly, the degree of the photo inhibition is alleviated, and the five parameters, α, Pnmax, LSP, LCP and Rday, are all increased. Whether under the circumstances of saturation light, unsaturation light or light inhibition, the right angle hyperbolic modified model and quadratic regression model could fit light response curve of corn better under different nitrogen levels, the fitted photosynthetic parameters are closer to the measured ones, so the two models are more suitable for fitting the corn light response curve.