不同氮肥水平下玉米光响应曲线模型的比较

【目的】本研究采用7种模型对光响应曲线进行拟合,比较不同拟合模型的优劣,旨在优选出氮胁迫下最优的光合作用光响应模型,为研究玉米的氮素营养生理和栽培提供科学依据,为棕壤地区春玉米氮素高效管理提供理论依据。【方法】以郑单958玉米为研究对象,在棕壤长期定位肥料试验的基础上,采用LI-6400型便携式光合作用测定系统测定穗位叶在不同光强下的光合速率,从不同供氮水平研究灌浆期玉米穗位叶叶片的光合作用光响应特征,采用二次回归、 直角双曲线、 非直角双曲线以及直角双曲线修正等7种不同模型对光响应曲线进行拟合,通过拟合程度、 拟合的表观量子效率(α)、 最大净光合速率(Pnmax)、 光饱和点(LSP)、 光补偿点(LCP)和暗呼吸速率(Rday)6个参数的对比,比较7 种模型的差异。【结果】 1)随氮肥水平的提高,产量、 氮素含量、 叶绿素含量有所提高,而施氮处理的净光合速率则表现出降低的趋势。2)本研究中的7种模型均能较好地对施高量氮肥(N180处理)的玉米叶片Pn光响应进行拟合,决定系数除直角双曲线修正模型为0.992外,其余均为0.994。但是不同模型对光抑制现象明显的N0、 N120处理的拟合效果差异较大,从决定系数比较来看,拟合效果优劣排序为直角双曲线修正模型、 二次回归模型非直角双曲线模型指数模型直角双曲线模型、 动力学模型。3)直角双曲线修正模型和二次回归模型的Pnmax、 LSP、 LCP和Rday四个光合参数均与实测值较为接近,而其他模型除个别参数较为接近外,多数参数差别较大;另外由于直角双曲线模型、 非直角双曲线模型和动力学模型的方程没有极值,不能直接得到光饱和点,使这三种模型损失了LSP这个重要的参数。4)随着施氮水平的提高,灌浆期玉米穗位叶α、 Pnmax、 LSP、 LCP和Rday 5个参数均逐渐升高。【结论】随着施氮水平的提高,灌浆期玉米穗位叶光合性能明显提升,光抑制程度减轻,α、 Pnmax、 LSP、 LCP和Rday 5个参数均升高;在不同氮肥水平下,无论是光饱和、 非光饱和或光抑制情况下,直角双曲线修正模型和二次回归模型均能较好地对玉米光响应曲线进行拟合,拟合的光合参数信息较多,拟合的光合参数与实测值相近,因此直角双曲线修正模型和二次回归模型较适宜拟合玉米光响应曲线。

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.