A field experiment was conducted to study the effects of five irrigation treatments on diurnal variations in flag-leaf photosynthesis and yield of "Qingmai 6" dryland wheat variety. The results showed that diurnal variations in net photosynthetic rate (Pn) in each treatment followed a double-peak curve. However, the degree of midday depression in photosynthesis increased with increasing amount of irrigation. Increasing irrigation amount enhanced flag-leaf Pn and net stomatal conductance (Gs) under ≤3 irrigation times. The maximum Pn and Gs appeared in W3 treatment (I.e., 60 mm irrigation each at jointing, booting and grain-filling stages). With increasing supplementary irrigation, intracellular CO2 concentration and stomatal limitation (Ls) decreased. Flag-leaf Pn under W4 treatment (I.e., 60 mm irrigation each at sprouting, jointing, booting and grain-filling stages) was significantly lower than that under W3 treatment. This suggested that superfluous irrigation had negative effects on flag-leaf photosynthesis in dryland winter wheat at grain-filling stage. In all the treatments, yield under W2 treatment (I.e., 60 mm irrigation each at jointing and booting stages) was the highest. The difference in yield between W2 and W1 (I.e., 60 mm irrigation at jointing stage) treatments was insignificant. Under ≤2 times of irrigation, yield increased with increasing irrigation amount. Yields under W3 and W4 treatments werelower than that under the dryland control treatment. This suggested that superfluous irrigation was unsuitable for high yield dryland winter wheat cultivation. In all the treatments, water production efficiency (WPE) declined with increasing irrigation amount. The experiment suggested that irrigation at jointing, booting and grain-filling stages was crucial for high flag-leaf Pn in dryland winter wheat. However, the effect of irrigation at sprouting stage on flag-leaf photosynthesis of dryland winter wheat was insignificant. Jointing was the most pivotal stage for high yield of wheat. Jointing and booting were the most essential stages for irrigating of winter wheat. Dryland wheat irrigation at these stages was very important for high yield and WPE. In terms of yield and WPE, the optimal supplementary irrigation mode for high yield in dryland winter wheat was 60 mm at jointing stage.%在大田条件下,以“青麦6号”小麦为试验材料,研究了5个灌水处理下旱地冬小麦灌浆期旗叶光合特性日变化和产量的变化.结果表明.5个灌水处理净光合速率日变化曲线均为双峰曲线,但随着灌水次数的增加,“午休”明显减弱.在灌溉低于3水的情况下,旗叶的净光合速率、气孔导度都随灌溉量的增加呈上升趋势,均以灌3水(W3,拔节水60 mm+孕穗水60 mm+灌浆水60 mm)处理最高,而胞间CO2浓度和气孔限制值随着灌溉量的增加呈下降趋势；而灌溉4水(W4,起身水60 mm+拔节水60 mm+孕穗水60mm+灌浆水60 mm)处理的净光合速率明显小于W3处理,表明过量灌溉对旱地小麦灌浆期旗叶的光合作用有消极作用.小麦产量以灌2水(W2,拔节水60 mm+孕穗水60 mm)处理为最高,且在灌溉2水以下随着灌溉次数增加而增加,但灌l水(W1,拨节水60 mm)和W2处理间产量差异不显著,同时灌溉3水(W3)和4水(W4)会使产量下降,反而低干旱地处理,因此过多灌水不利于旱地小麦的高产.试验结果还表明,拨节期、孕穗期和灌浆期灌溉对旱地小麦旗叶灌浆中期达到较高光合作用至关重要,而起身水对旱地小麦光合作用无显著影响.拔节期是旱地小麦达到高产最重要的灌溉时期,拔节～孕穗期为冬小麦需水关键期,拔节～孕穗水对冬小麦产量和水分利用效率有重要影响.水分生产效率也随着灌水量的增加呈下降趋势.综合产量和水分利用效率因素,以灌溉拔节水60mm(W1)处理为达到旱地冬小麦高产的最佳灌溉模式.
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