短梗大参光合作用光响应曲线及模型拟合

Photosynthetic light response curves of Macropanax rosthornii and their model fitting

为了探讨不同光合作用光响应模型对短梗大参光合特性的适用性,采用LI-6400便携式光合仪分别观测了全光照和荫蔽环境下的5年生短梗大参叶片的光响应曲线;并应用二次多项式模型、分段函数、直角双曲线模型、非直角双曲线模型和修正的直角双曲线模型拟合短梗大参的光响应曲线,根据拟合效果筛选不同光照环境下短梗大参合适的光响应模型。结果表明:1在全光照环境下,短梗大参光合作用的光响应曲线属于饱和趋近型;直角双曲线模型、非直角双曲线模型和修正的直角双曲线模型无法直接求取其最大净光合速率和光饱和点的解析解;二次多项式回归模型拟合的光合参数值与实测值相差很大;分段函数为全光照下短梗大参光响应曲线最适用的分析模型,其拟合的初始量子效率为0.047,最大净光合速率为10.70μmol·m-2s-1,光饱和点为1 333.33μmol·m-2s-1,光补偿点为10.43μmol·m-2s-1,暗呼吸速率为0.48μmol·m-2s-1。2在荫蔽环境下,短梗大参光合作用的光响应曲线为中度抑制型;二次多项式拟合的光合参数值与实测值差异明显;分段函数拟合的光合参数值则比实测值要低;直角双曲线模型和非直角双曲线模型拟合的光饱和点均明显低于实测值;修正的直角双曲线模型为荫蔽环境下短梗大参光响应曲线分析的最适用模型,其拟合的初始量子效率为0.076,最大净光合速率为5.07μmol·m-2s-1,光饱和点为449.60μmol·m-2s-1,光补偿点为2.79μmol·m-2s-1,暗呼吸速率为0.21μmol·m-2s-1。

The leaf light response curves of 5-year-old Macropanax rosthornii grown under full sunlight and shade were respectively measured by LI-6400 portable photosynthesis system to study the application of photosynthetic light response models to M. rosthornii photosynthesis. The light response curves of M. rosthornii were fitted with the models of quadratic polynomial regressions, subsection function, rectangular hyperbola, non-rectangular hyperbola and modified rectangular hyperbola, and appropriate models were selected based on the fitting effect. The results were as follows： ① Under full sunlight, the photosynthetic light response curve of M. rosthornii was a saturation and approach type of light response curve; the analytical solutions of maximum net photosynthetic rate and light saturation point were not able to be directly obtained by rectangular hyperbola, non-rectangular hyperbola and modified rectangular hyperbola; the prediction values of quadratic polynomial regressions were distinctly different from the measured data. The most proper photosynthetic model of M. rosthornii under full sunlight was the subsection function, the fitted initial quantum yield was 0.047, and the fitted maximum net photosynthetic rate, light saturation point, light compensation point and dark respiration rate were 10.70, 1 333.33, 10.43 and 0.48 μmol·m-2s^-1, respectively. ② Under shade, the photosynthetic light response curve of M. rosthornii was a mid-intensity suppression type of light response curves; the prediction values of quadratic polynomial regressions were distinctly different from the measured data and the prediction values of subsection function were slightly smaller than the measured data; the light saturation point fitted by rectangular hyperbola or non- rectangular hyperbola was notably smaller than the measured light saturation point; the most proper photosynthetic model of M, rosthornii under shade was the modified rectangular hyperbola, and the fitted initial quantum yield was 0.067, and the fitted maximum net photosynthetic rate, light saturation point, light compensation point and dark respiration rate were 5.07,449.60, 2.79 and 0.21μmol·m-2s^-1 respectively.