遮荫条件下O_3胁迫对冬小麦气孔导度影响的模拟

为了探究在遮荫条件下地表O3浓度增加对冬小麦气孔导度的影响,开展了两种不同强度遮荫与开顶式气室（OTC）相结合的大田试验,设置3个处理组：O3浓度为（100±9）nL.L-1结合（60±5）%遮荫的处理组（T1）;O3浓度为（100±9）nL.L-1结合（20±5）%遮荫的处理组（T2）;O3浓度为（100±9）nL.L-1不作遮荫的处理组（CK）。利用SC-1型气孔导度仪测定了3个处理组冬小麦不同生育期的气孔导度值。综合分析了生育期和O3胁迫,以及水汽压差（VPD）、温度（T）、光照（PAR）环境因子的变化对冬小麦气孔导度的影响,采用修正后的Jarvis非线性气孔导度模型模拟了3个处理组的气孔导度值。结果表明：遮荫对大田环境因子均产生了影响,其中,T1、T2处理组8：00—16：00点的平均温度和水汽压差较CK相比分别下降了5.6℃、4.1℃和0.84kPa、0.74kPa;用该模型得到的气孔导度模拟值与观测值进行了比较,R2=0.88,表明模型模拟效果良好;同时,根据O3吸收通量模型计算出T1、T2和CK处理组在整个O3熏蒸时期,冬小麦O3累积吸收通量分别为14.92、15.52、16.23mmolO3.m-2,并由此建立了O3吸收通量（x）与干物质损失（y）的关系分别为：y=1.0-0.038x和y=1.0-0.022x,表明在相同O3胁迫条件下,遮荫导致了冬小麦O3累积吸收通量的差异,在60%和20%遮荫条件下,O3吸收通量增加10mmol.m-2,与CK相比,其干物质累积损失分别为38.0%和22.0%。

Simulative Research into Ozone Stress on Stomatal Conductance of Winter Wheat Under Different Shading Conditions

To assess the stomatal conductance responses of winter wheat to surface CO3 increase （ Tritic um oestivuml.,YangMai 13 ） in shad- ings two field experiments were conducted inside open-top-chambers （OTC）. Three treatments （T1, T2 and CK） were designed as follows ： a ） T1 consisted of CO3 concentration reaching （100±9 ）nL. L^-1 in combination with （60±5）% shading; b ） T2 of （100±9）nL. L^-1 and （20±5）% shading; c ）of （ 100±9 ）nL. L^-1 and no shading denoted as control test（CK）. ASC-1 stomata! conductance device was used to measure the con- ductance in different growth periods of the wheat development in the treatments. Afterward, comprehensive analysis was made of the impact upon the conductance in growth stages and ozone stress of vapor pressure difference （VPD）, temperature （T） and Photosynthetically Active Radiation（PAR ）, followed by utilizing revised Javis nonlinear stomatal conductance model to study the conductance values of the three treat- ment groups. Results showed that shading exerted effect on the field environmental factors, and in particular, the mean T and VPD in T1 and T2 dropped by 5.6 ℃ and 4.1 ℃ and 0.84 kPa and 0.74 kPa, respectively as compared to CK over 8：00--16：00 BST. The model-given con- ductances were compared with the observations demonstrating R^2=0.88, indicating that the modelings were good enough. On the basis of mod- el-calculated crop ozone flux uptake we found the accumulative absorption fluxes during the smudging to arrive at 14.92 mmol O3. m^-2, 15.52mmol O3.m^-2 and 16.23 mmol O3.m^-2, respectively, for T1, T2 and CK, whence the relations between ozone uptake flux（x ） and dry matter loss （y） were established in the form of y= 1.0-0.038x and y= 1.0-0.022x, thereby showing that under the same ozone stress the different-degree shading led to difference in cumulative ozone uptake flux, and for 60% and 20% screening the dry matter loss reached 38.0% and 22.0%, in order, for T1 and T2 in comparison with CK, when the accumulated uptake flux increased by 10 mmol.m^-2.