叶片气体交换参数是作物产量形成的生理基础,其中光合速率和蒸腾速率决定了叶片水分利用效率,对作物抗旱节水研究具有重要意义。在定西和武威两个试验站进行春小麦盆栽水分模拟试验,设置对照（CK）、持续干旱（WS）、中旱（40%FC）和重旱（30%FC）4组处理,分析不同水分条件下春小麦叶片气体交换参数和水分利用效率（WUE_inst）的变化特点及其相关特征。结果表明：（1） 持续干旱胁迫下,春小麦的土壤日耗水量、光合速率、蒸腾速率和气孔导度均呈先快后慢的下降趋势,达到中旱和重旱水平时相比CK分别减小了71%和76%、39%和60%、57%和66%、60%和77%,受影响程度为：气孔导度>蒸腾速率>光合速率,胞间CO₂浓度在轻旱-中旱时下降,中旱后期降幅达33%,之后呈上升趋势,WUE_inst在轻旱-中旱阶段上升,中旱后期时增加41%,之后下降,相比于CK,轻-重度胁迫会提高WUE_inst,极度干旱则使之降低;（2） 当水分胁迫维持在中旱或重旱水平时,以上各指标均会维持在持续干旱达到相同干旱等级时对应的值附近,且中旱时值均高于重旱时的数值（P<0.05）;（3） 在持续干旱胁迫的轻旱-中旱阶段,净光合速率和蒸腾速率互为主导影响因子,而在持续干旱胁迫之后的阶段,以及胁迫维持在中旱或重旱情形下,两者的主导因子均为气孔导度,WUE_inst在水分充足—持续干旱胁迫时均以蒸腾速率为主导因子,而当胁迫维持在中旱或重旱时其受叶片气体交换参数的调控作用不明显。本研究结果可为作物在不同干旱阶段和情形下采取适当措施进行抗旱节水提供参考依据。

Leaf gas exchange parameters are the physiological basis of crop yield. Among these parameters, the photosynthetic and transpiration rates play a decisive role in leaf water use efficiency. Therefore, they are essential to research on crop drought resistance and water conservation. Potted water simulation experiments were conducted in spring wheat at Dingxi and Wuwei stations. Four group of treatments, including the control (CK), continuous drought stress (WS), moderate drought stress (40%FC), and severe drought stress (30%FC) treatments, were established to analyze the response characteristics and related characteristics of the gas exchange parameters and water use efficiency (WUE_inst) of spring wheat leaves under different levels of water stress. Under continuous drought stress, the daily soil water consumption, photosynthetic rate, transpiration rate, and stomatal conductance of spring wheat all showed an initially rapid and then slow downward trend. When the stress reached moderate and severe drought, these parameters were decreased by 71% and 76%, 39% and 60%, 57% and 66%, and 60% and 77%, respectively. The extent of reduction was stomatal conductance>transpiration rate>photosynthetic rate. The intercellular CO₂ concentration decreased during mild to moderate drought, and it was decreased by 33% under late moderate drought stress. Subsequently, an increasing trend was observed. WUE_inst showed an upward trend during the stage from mild to moderate drought. It was increased by 41% at the late moderate drought stage, and then it decreased rapidly. Compared with CK, WUE_inst increased during mild to severe drought, and it reduced after extreme drought. However, when water stress was maintained at the level of moderate or severe drought, the above indicators were similar at the same drought level under continuous drought. Additionally, the values of moderate drought were all higher than those of severe drought (P<0.05). The photosynthesis and transpiration rates were the dominant factors for each other under the mild to moderate stage of continuous drought stress, and stomatal conductance was their common dominant factor under this stress after the late moderate drought and when water stress was maintained at moderate or severe drought. WUE_inst was dominantly influenced by the transpiration rate under well-watered and continuous drought stress, and it was not significantly regulated by leaf gas exchange parameters when water stress was maintained at moderate or severe drought. The research results provide a reference for informing the use of appropriate measures in different drought stages and situations.