CO2浓度升高对半干旱区春小麦光合作用及水分生理生态特性的影响

大气CO₂浓度升高已成为世界范围内重要环境问题。为了解大气CO₂浓度升高对春小麦光合作用及水分生理生态特性的影响,在典型半干旱区定西利用开顶式气室(OTC)试验平台,以春小麦“定西24号”为供试品种,开展了CO₂浓度增加模拟试验。试验设对照(390μmol·mol^?1)、480μmol·mol^?1和570μmol·mol^?1等3个CO₂浓度(摩尔分数)梯度。结果表明:在对照和增加CO₂浓度条件下,春小麦叶片净光合速率和蒸腾速率日变化均呈“双峰型”分布,出现明显的“午休”现象;胞间CO₂浓度的日变化表现为斜“V”字型曲线;叶水势日变化呈现反抛物线曲线走向,在中午后出现水势曲线拐点。在不同生育时期内,净光合速率、气孔导度和胞间CO₂浓度均表现为开花期最大,乳熟期最小。而蒸腾速率表现为开花期最大,拔节期最小,叶片水平水分利用效率表现为孕穗期最大,乳熟期最小。随着CO₂浓度升高,春小麦叶片净光合速率、胞间CO₂浓度、水分利用效率和水势提高,气孔导度和蒸腾速率降低。与对照大气CO₂浓度相比,在480μmol·mol^?1浓度和570μmol·mol^?1浓度下,整个生育期净光合速率平均分别提高了14.68%和28.20%,气孔导度平均降低了15.29%和24.83%,胞间CO₂浓度平均提高了10.38%和26.15%,蒸腾速率平均减小了6.63%和12.41%,WUE平均增加了22.9%和46.9%。随着CO₂浓度升高,蒸腾失水减少,叶片水势不断增加,从而增强了春小麦对干旱胁迫的抵御能力。研究结果为我国半干旱区春小麦对全球气候变化下的敏感性及适应性提供理论参考。

Effects of Elevated CO2Concentration on the Characteristics of Photosynthesis and Water Physiological-ecological of Spring Wheat in Semi-arid Area in China

The increase of atmospheric CO₂concentration has become an important environmental problem worldwide.In the present study,the effects of elevated CO₂concentration on the characteristics of photosynthesis and water physiological-ecological of spring wheat(Dingxi 24#)were investigated based on the Open-Top Chamber(OTC)experiment platform in Dingxi which was located in semi-arid area of the loess plateau in central Gansu.Three different CO₂concentrations experiments(390μmol·mol^?1,480μmol·mol^?1and 570μmol·mol^?1)were involved.The results showed that under ambient air CO₂concentration and elevated CO₂concentration levels,the diurnal variation of net photosynthetic rate(Pn)and transpiration rate(Tr)in spring wheat leaves presented a two peaks curve,significant midday depression of photosynthesis and transpiration was appeared,the diurnal variation of internal CO₂concentration(Ci)in spring wheat leaves appeared“V”shape,and the diurnal variation of leaf water potential presented the trend of the anti-parabolic curve,the inflection point of the water potential curve appeared after noon.At different growth stages,Pn,stomatal conductance(Cs)and Ci were the highest at flowering stage and the lowest at milk stage.Tr was the highest at flowering stage and the lowest at jointing stage.Water use efficiency(WUE)was the highest at booting stage and the lowest at milk stage.Pn,Ci,WUE and water potential increased but Cs and Tr decreased with the increase of CO₂concentration.Under 480μmol·mol^?1and 570μmol·mol^?1,the average of Pn increased by 14.68%and 28.20%respectively,the Cs decreased by 15.29%and 24.83%,the Ci increased by 10.38%and 26.15%,the Tr decreased averagely by 6.63%and 12.41%,and WUE increased by 22.9%and 46.9%in the whole growth period compared to the ambient air CO₂concentration.With the increase of CO₂concentration,the loss water induced by transpiration decreased and leaf water potential increased,which enhanced the resistance of spring wheat to drought stress.Our results provide a theoretical reference for the sensitivity and adaptability of the spring wheat in the semi-arid area of China under the global climate change scenarios.