滴灌冬小麦不同施氮量下光合-气孔导度耦合模拟和验证

Simulation and verification of photosynthesis-stomatal conductance coupled model under different nitrogen application rates in winter wheat with drip irrigation

针对华北平原冬小麦田过量施氮(N)现象,构建和参数化不同施N量下光合-气孔导度耦合模型有利于理解降低施N量对作物产量影响的生理基础。该文于2013—2014年连续2个生长季在滴灌冬小麦田设置3种施N量:290、190和110 kg/hm2,开展了光合及相关生理因子的测定,确定了光合-气孔导度耦合模型关键参数。结果表明:最大羧化速率V_(cmax)在84.5~153.3μmol/(m2·s)之间变化,V_(cmax)与叶片N含量之间的可用线性关系来量化;最大电子传递速率J_(max)在156.5~236.2μmol/(m2·s)之间变化,二者比值在处理间差异不显著;推导光合模型和气孔导度Ball-Berry模型联立的解析解来求解耦合模型,能较好模拟光合速率日进程,对2次测定模拟的平均绝对误差分别为2.11和2.23μmol/(m2·s)。通过对环境因子及生理因子差异的综合分析,模型可用于模拟施N条件下的光合速率变化,从而为较准确地预测小麦产量奠定基础。

Aiming at the phenomenon of excess nitrogen （N） application rate in winter wheat field in North China Plain, measuring and modelling photosynthetic rates under different N rates is helpful to understand the physiological basis of the influence of reducing traditional N application rates on crop yield. This study set up 3 amounts of N rates, i.e. 290, 190 and 110 kg/hm2, as high （N3）, middle （N2） and low N （N1） treatments, respectively in drip irrigation winter wheat field in 2 consecutive growing seasons （2012-2014）. The coupled model of photosynthesis and stomatal conductance was established to model photosynthetic rates. Photosynthetic rates to intercellular CO2concentration response curves （An-Cicurves） were measured in 2014 to determine key parameters of the model from the heading stage to harvest stage. Daily dynamics of photosynthetic rates were measured in 2013 as the verification data of the coupled model. The results showed that the apparent maximum carboxylation rate of Rubisco （Vcmax） and maximum electron transfer rate （Jmax） was significantly affected by N treatments.The measured Vcmaxvaried from 84.5 to 153.3 μmol/（m2·s）and Jmaxvaried from 156.5 to 236.2 μmol/（m2·s）during the measurements and among treatments. Differences of Vcmaxand Jmaxamong treatments were more significant when the measurement dates close to the harvest stage. During the filling stage （May 21stto 23rd）, only Vcmaxand Jmaxof the low N treatment （N1） was significantly lower than that of high N treatment （N3）, the corresponding values of the middle N treatment （N2）were not significant lower than those of N3.During the milking stage（June 2ndto 3rd）,however,the Vcmaxand Jmaxof both N2 and N1 were significantly lower than those of N3. There was no significant difference in the ratio of Jmax/Vc maxamong treatments during the three measurements. The ratio of Jmax/Vc maxgradually increased along with the advancing of growing stages and changed from 1.49 to 2.00 during the measurements.The differences of Vcmaxamong treatments could be quantified by leaf mass N content.Then the Jmaxvalue can be calculated according to the ratio of Jmax/Vc max.The slope（g1）and intercept （g0） of the stomatal conductance sub-model were changed with different N application. During the filling stage （May 21stto 23rd）, it was found that the N3 treatment with the highest g0and the smallest g1. The analytical solution of the photosynthesis model and the Ball-Berry stomatal conductance model was derived to solve the coupled model. Considering the difference between the key parameters, the simulation results of the coupling model for photosynthetic rate from the daily process was good, with the average absolute error were 2.11 and 2.23 μmol/（m2·s） for the 2 measurements in 2013 and the differences between simulated and measured photosynthetic rate were less than 5%. The prediction of the model also showed that different parameters have different effects on the simulation results of photosynthetic rate. For example, although the g0of stomatal conductance sub-model is often relatively small, it will cause large error in the simulation of photosynthetic rate under low light intensity, while some researchers may neglect this parameter when running the model. The model can be used to simulate photosynthetic rates under change of single physiological or environmental factor and change of multi factors, so as to better predict the yield changes.