冬小麦气孔臭氧通量拟合及通量产量关系的比较分析

基于田间原位开顶箱(Open-Top Chambers,OTCs)实验,研究了不同浓度臭氧(O3)处理下(自然大气处理,AA;箱内大气处理,NF;箱内低浓度O3处理,NF+40 nL/L;箱内中等浓度O3处理,NF+80 nL/L;箱内高浓度O3处理,NF+120 nL/L),冬小麦(Triticum aestivum L.)旗叶气孔运动对不同环境因子的响应,并通过剂量反应分析,比较了冬小麦产量损失与累积气孔O3吸收通量(AFstX)和累积O3暴露浓度(AOT40和SUM06)的相关性差异。结果表明:冬小麦旗叶气孔运动的光饱和点和最适温度分别约为400μmol.m-.2s-1和27℃,水汽压差、土壤含水量和O3剂量的气孔限制临界值分别约为1.4 kPa、-100 kPa和20μL.L-.1h-1,超过此临界值时,气孔导度会明显下降。利用Jarvis气孔导度模型对冬小麦旗叶气孔导度和气孔O3吸收通量进行了预测,结果表明Jarvis模型解释了冬小麦实测气孔导度60%的变异性。由于不同时期植物体气孔导度的差异,冬小麦旗叶生长期内累积气孔O3吸收通量(AFstX)呈非线性增加趋势。O3吸收速率临界值(X)为4 nmol.m-.2s-1时,累积O3吸收通量(AFst4)与冬小麦产量的相关性最高(R2=0.76),该数值介于O3暴露指标AOT40和SUM06的剂量反应决定系数(0.74和0.81)之间。与O3浓度指标(AOT40和SUM06)相比,O3通量指标(AFstX)在本试验冬小麦产量损失评价中未表现出明显优势。

Stomatal ozone uptake modeling and comparative analysis of flux-response relationships of winter wheat

An Open-Top Chambers(OTCs) experiment on field-grown winter wheat(Triticum aestivum L.) was conducted for the purpose of studing the relationships between stomatal conductance(gs) of wheat flag leaves and different environmental variables.Dose-response analysis was also made in order to compare the performance of flux-based and exposure-based indices in predicting the yield loss of winter wheat.Five different ozone(O3) treatments(Ambient air,AA;Non-filtered air,NF;Non-filtered air with additional O3 of 40 nL/L,NF+40;Non-filtered air with additional O3 of 80 nL/L,NF+80;and Non-filtered air with additional O3 of 120 nL/L,NF+120) were adopted.1471 data points of gs were obtained from twelve measurements through the experiment.Based on the boundary-line analysis,the limiting effects of environmental variables on gs of wheat flag leaves were analyzed.A typical light response curve was found for gs with light saturation at approximately 400 μmol·m-2·s-1 photosynthetically active radiation(PAR).The response of gs to air temperature(T) was characterized by a typical single-peak curve with the physiological optimum temperature at 27 ℃.The critical values for gs responses to water vapor pressure deficit(VPD),soil water potential(SWP) and O3 dose(AOT0) were approximately 1.4 kPa,-100 kPa and 20 μL·L-1·h,respectively,and gs decreased sharply when the critical values were exceeded.A Jarvis type multiplicative model was drawn up and parameterized to predict gs and stomatal O3 uptake(AFstX) of wheat flag leaves from environmental variables(PAR,T,VPD,SWP and AOT0),which were measured continuously through the experiment.Approximately 60% variation of measured gs could be accounted for by the Jarvis type model.Different phenological variations were found for exposure-based indices(AOT40 and SUM06) and flux-based index(AFstX).Due to the variation of gs which was affected by environmental factors and plant development,accumulated stomatal O3 uptake increased nonlinearly during the growing period of wheat flag leaves.The relationship between relative yield loss and accumulated stomatal O3 uptake(AFstX),using a threshold(X) for the O3 uptake rate of 4 nmol·m-2·s-1,provided a higher R2-value(0.76) than AFstX with any other threshold,and this R2-value was between those of relationships based on AOT40(0.74) and SUM06(0.81).Compared to exposure-based indices(AOT40 and SUM06),flux-based index(AFstX) represented no significant advantage for the risk assessment of O3 on winter wheat in our experiment.