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在半干旱黄土丘陵区,以2年生盆栽山杏为材料,应用CIRAS-2型光合作用系统,测定了8个土壤水分梯度下山杏光合作用的CO2响应过程,并采用直角双曲线模型、指数方程和直角双曲线修正模型对其CO2响应数据进行拟合,分析了山杏光合作用与土壤水分的定量关系.结果表明:山杏CO2响应过程对土壤水分有明显的阈值响应特征.维持山杏叶片较高的光合速率(Pn)和羧化效率(CE)的土壤相对含水量(RWC)在46.3%～81.9%,在此水分范围内,光合作用没有发生明显的CO2饱和抑制现象;当RWC超出此范围,土壤水分升高或降低均明显降低山杏叶片的光合能力(Pnmax)、CE和CO2饱和点(CSP).在不同土壤水分条件下,3个模型对山杏CO2响应数据的模拟效果有明显差别.在46.3%～81.9%土壤水分范围内,3个模型均能较好地拟合山杏CO2响应过程及其特征参数CE、CO2补偿点(Γ)和光呼吸速率(Rp),其拟合精度均表现为直角双曲线修正模型>指数方程>直角双曲线模型;当土壤水分含量过高(RWC>81.9%)或过低(RWC<46.3%)时,只有直角双曲线修正模型能较好地拟合山杏CO2响应过程及其特征参数.RWC在46.3%～81.9%范围内,山杏具有较高的光合作用效率;与传统直角双曲线模型和指数方程相比,直角双曲线修正模型具有更好的适用性.
In semi-arid hilly Loess Plateau, the biennial potted Prunus armeniaca was used as the material, and the CIRAS-2 photosynthesis system was used to determine the CO2 response of apricot photosynthesis under eight soil moisture gradients. The quadratic hyperbola model and exponential equation And rectangular hyperbolic model were used to fit the CO2 response data and the quantitative relationship between photosynthesis and soil moisture was analyzed.The results showed that there was a significant threshold response characteristic to the soil moisture in the response of Armeniaca sibirica The relative soil water content (RWC) of photosynthesis rate (Pn) and carboxylation efficiency (CE) ranged from 46.3% to 81.9%. No significant CO2 saturation suppression occurred under photosynthesis in this moisture range. When RWC exceeded In this range, both Pnmax, CE and CO2 saturation point (CSP) of P. apricot leaves were significantly decreased by both increasing and decreasing of soil moisture.The simulation results of the three models on the response data of P. armeniaca under different soil moisture conditions (P <0.05), the three models all fit the response of Armeniaca spp.and the characteristic parameters CE, CO2 compensation point (Γ) and photorespiration rate (Rp) within the range of 46.3% ~ 81.9% Fitting accuracy are shown as straight Angle hyperbola correction model> exponential equation> rectangular hyperbola model. Only the rectangular hyperbolic correction model can well fit the mountain when the soil moisture content is too high (RWC> 81.9%) or too low (RWC <46.3% Apricot CO2 response process and its characteristic parameters.RWC was in the range of 46.3% ~ 81.9%, and Prunus armeniaca had higher photosynthetic efficiency. Compared with the traditional rectangular hyperbola model and exponential equation, the modified hyperbolic curve model had better applicability.