【摘要】 运用LI-6400便携式光合作用系统测定了不同光强(2 000、1 500、1 000和500μmol·m–2·s–1)和两种O2浓度(21%和2%的O2)下冬小麦(Triticum aestivum)灌浆期旗叶的CO2响应曲线,比较了现有CO2响应模型(生化模型、直角双曲线模型和直角双曲线修正模型)拟合给出光下(暗)呼吸与测量值之间的差异。结果显示,直角双曲线修正模型所给出的光下呼吸速率拟合值与测量值最为接近。植物光合作用对大气CO2响应(A/Ca)的拟合结果优于光合作用对胞间CO2浓度(A/Ci)的拟合。然而,所有模型基于A/Ca拟合的光下(暗)呼吸在整体上与测量值存在显著差异(p<0.05),推测与现有模型没有考虑CO2浓度对光呼吸和光下暗呼吸速率的影响有关。对小麦的试验结果表明,CO2浓度对光呼吸和光下暗呼吸均有显著影响:随着CO2浓度的增加(0–1 400μmol·mol–1),不同光强下的表观光呼吸变化范围分别为5.035–11.670、4.222–11.650、4.330–10.999和3.263–9.094 μmol CO2·m–2·s–1;光下暗呼吸的变化范围分别为0.491–2.987、0.457–2.955、0.545–3.139和0.448–3.139 μmol CO2·m–2·s–1。回归分析发现,表观光呼吸和光下暗呼吸与CO2浓度之间均存在较好的相关性。然而,将该回归关系整合到现有模型中,是否会优化模型,从而提高模型对相关光合参数估算的准确性尚有待于进一步研究。更多还原

【Abstract】 Aims The objective of this study was to compare the values of respiration under light derived by fitting a photosynthetic CO2 response model and measurements, in order to provide information for model optimization. Methods Using combined gas exchange measurements and a low O2(2% O2) method, the responses of photosynthetic rate(Pn) to CO2 at different light intensities(2 000, 1 500, 1 000 and 500 μmol·m–2·s–1) in the flag leaves of wheat were measured. The measured data were fitted by a biochemical model, a rectangular hyperbola model and a modified rectangular hyperbola model of the photosynthetic response to intercellular CO2 concentration(A/Ci) and air CO2 concentration(A/Ca), aiming to approach the reasonability of the fitted results obtained from the models. Important finding The sequence of fitting effect of the three CO2 response models in descending order was as follows: modified rectangular hyperbola model > rectangular hyperbola model > biochemical model. Fitted values of A/Ca curve was more reasonable than A/Ci curve, because the photorespiration and mitochondrial respiration under light(Rd) estimated by the former better matched the measured values. However, there were significant differences in the whole between the fitted and measured values. The reason could be that the effect of CO2 concentrations on Rd and apparent photorespiration(Rpa) is neglected in all the current CO2 response models. Our results showed that CO2 concentration had a marked effect on Rpa and Rd. With increasing CO2 concentration, Rpa and Rd increased first, and then decreased sharply. Take 2 000 μmol·m–2·s–1 for example, Rpa varied between 5.035 and 11.670 μmol CO2·m–2·s–1, and Rd varied between 0.491 and 2.987 μmol CO2·m–2·s–1. Regression analysesindicated that Rpa and Rd were well related to CO2 concentrations at different light intensities.更多还原