CO_2浓度升高对不同水分条件下冬小麦生长和水分利用的影响

Effects of elevated CO_2 concentration and different water conditions on winter wheat growth and water use

以CO2浓度升高为主要特征的气候变化对作物生长发育及产量形成的影响日益受到重视。冬小麦是我国主要粮食作物之一, 主要分布在干旱及半干旱地区, 且生长期内多干旱少雨。研究不同水分条件下冬小麦的生长变化及水分利用对CO2浓度升高的响应具有重要的科学和实践意义。本研究在封顶式生长室中对2个土壤水分水平[适宜水分： 70%~80%田间持水量; 干旱胁迫： 50%~60%田间持水量]的盆栽冬小麦进行了CO2熏蒸试验[背景大气浓度： （396.1±29.2） μmol·mol-1; 升高的浓度： （760.1±36.1）μmol·mol-1]。对小麦植株生理指标、生物量、产量、耗水量和水分利用效率（WUE）等的研究结果表明, 与背景大气CO2浓度相比, CO2浓度升高可促进冬小麦生长, 其地上生物量显著增加, 适宜水分和干旱胁迫条件下分别增加了28.6%和18.6%; 籽粒产量显著增加, 适宜水分和干旱胁迫条件下分别增加了32.6%和22.6%; CO2浓度升高主要通过增加穗粒数提高籽粒产量, 穗粒数在适宜水分条件下提高24.3%, 干旱胁迫条件下提高15.5%, 对千粒重没有显著影响。CO2浓度升高使群体和产量WUE显著提高, 在适宜水分条件下提高幅度较大, 分别提高17.7%和24.8%。CO2浓度升高显著提高了叶片光合速率（Pn）、降低了气孔导度（Gs）和蒸腾速率（Tr）; 在适宜水分和干旱胁迫下Pn分别提高15.6%与12.9%, Gs分别降低22.7%与18.2%, Tr分别降低8.9%与7.5%。CO2浓度升高提高了叶片水势及叶绿素含量; 在适宜水分条件下叶片水势提高幅度较大, 为7.7%; 叶片叶绿素含量在2种水分条件分别提高7.5%与3.8%。由以上试验结果可得出： CO2浓度升高对冬小麦的生长、产量及水分利用效率均具有促进作用, 而且在土壤水分状况较好时, 这种作用效果更明显; CO2浓度升高主要通过增加穗粒数来促进产量提高。

Elevated CO2 concentration has been the main cause of climate change and has gained considerable attention due to its important impacts on crop growth and yield formation. Winter wheat, a major food crop in China, is mainly cultivated in the arid and semiarid regions of the country. It is therefore critical to study the growth and water use of winter wheat under different water and CO2 conditions. In this study, winter wheat was grown in a pot experiment in closed chambers subjected to two concentrations of CO2 [（396.1±29.2） μmol·mol-1 （A） and （760.1±36.1） μmol·mol-1 （E）] and two soil water contents [70% 80% （sufficient） and 50% 60% （drought） of field capacity]. Plant growth, aboveground biomass, grain yield and water use efficiency （WUE） at different stages were analyzed. The results showed that although elevated CO2 had no significant effect on plant height and ear length, it respectively increased biomass by 28.6% and 18.6% under sufficient and drought water conditions. Elevated CO2 also respectively increased grain number and grain yield by 24.3% and 32.6% under sufficient water conditions and by 15.5% and 22.6% under drought conditions. Elevated CO2 showed no significant effect on the 1000-grain weight. Elevated CO2 increased evapotranspiration respectively by 8.5% and 4.6% under sufficient and drought water conditions. It also respectively increased population WUE by 17.7% and 13.7% and grain WUE by 24.8% and 17.1% under sufficient and drought water conditions. Elevated CO2 increased Pn by 15.6% and 12.9%, decreased Gs by 22.7% and 18.2% and Tr by 8.9% and 7.5% under sufficient and drought water conditions, respectively. Chlorophyll and water potential also increased under elevated CO2. There was a higher increase in water potential （7.7%） under sufficient water conditions while chlorophyll increased respectively by 7.5% and 3.8% under sufficient and drought water conditions. The results suggested that the effect of elevated CO2 on winter wheat growth, yield and WUE also depended on water conditions. The positive effects exceed the negative effects under sufficient water conditions. Grain yield improvement under elevated CO2 and was mainly driven by increased grain number.