Water shortage is one of the major problems in wheat (Triticum aestivum L.) production in northern plain in China.Water-saving technique is most important in wheat cultivation. In this study, we adopted water-controlled irrigation based on measuring soil moisture to improve the fixed-amount irrigation strategy in previous studies. Using wheat cultivar Jimai 22, we measured the photosynthetic performance of flag leaf and dry matter accumulation and distribution in plant under two plant densities and three irrigation treatments. In the 2008-2009 growing season, the plant densities were 150 (M1) and 225 (M2) seedlings per square meter, and the irrigation treatments were designed as relative soil moisture (SM) of 65％ at jointing and 60％ at anthesis (W0), SM of 75％ at jointing and 75％ at anthesis (W1), and SM of 75％ at 7 d after jointing and 75％ at 7 d after anthesis (W2).In the 2009-2010 growing season, only one plant density (M1) was adopted, which showed better performance in yield and water use efficiency (WUE) in the 2008-2009 growing season. Besides, the irrigation treatments were adjusted to SM of 75％ at jointing and of 60％ at anthesis (W'0), SM of 85％ at jointing and 75％ at anthesis (W' 1), and SM of 85％ at 7 d after jointing and SM 75％at 7 d after anthesis (W'2). Under the same irrigation treatment, maximal photochemical efficiency of PSⅡ (Fv/Fm) and actual photochemical efficiency of PSII (φpsⅡ) under M1 density were higher than those under M2 density from middle to late grain-filling stage, and dry matter accumulation amount after anthesis and dry matter translocation amount to grains in M1 treatment were significantly higher than those in M2 treatment. Compared with W1 treatment, Fv/Fm and φPSⅡ of W2 treatment were significantly higher from middle to late grain-filling stage, and photosynthetic rate (Pn, evapotranspiration (Tr), leaf water use efficiency (WUEL), and stomatal conductance (Gs) were also higher in W'2. Under the M1 plant density, the dry matter accumulation amount after anthesis and its contribution to grains were higher in W2 than in WI treatment, whereas the grain yield and WUE of W2 treatment were significantly higher than those in Wl treatment. The changing tendency of dry matter accumulation and distribution, grain yield, and WUE were similar in both growing seasons. In wheat growing environment similar to the condition of this experiment, we propose the best plant density is 150 seedlings per square meter and the best irrigating both at jointing and anthesis is SM (0-140 cm soil layer) of 75％ at 7 d after both stages.%2008-2010年连续2个小麦生长季,选用高产小麦品种济麦22,采用测墒补灌的方法,研究土壤水分对不同密度小麦旗叶光合性能、干物质积累与分配、籽粒产量及水分利用效率的影响.第1年在150株m-2(M1)和225株m-2(M2)2个密度下设置3个土壤含水量处理,即拔节期65%+开花期60%(W0)、拔节期75%+开花期75%(W1)和拔节后7 d 75%+开花后7 d 75%(W2);第2年选用第1年的节水高产密度处理M1,但土壤含水量调整为拔节期75%+开花期60%(W'0)、拔节期85%+开花期75%(W'1)和拔节后7 d 85%+开花后7 d 75%(W'2).两种基本苗密度相比较,M1处理灌浆中后期的旗叶最大光化学效率(Fv/Fm)、实际光化学效率(ФPSⅡ)和开花后干物质积累量和干物质向籽粒转运量显著高于M2处理.W2处理灌浆中后期的旗叶Fv/Fm和ФPSⅡ显著高于W1处理,而W'2处理灌浆中后期的旗叶光合速率(Pn)、蒸腾速率(Tr)、单叶水分利用效率(WUEL)和气孔导度(Gs)均显著高于W'1处理.在M1密度下,W2处理的干物质向籽粒的转运量,开花后干物质积累量及其对籽粒的贡献率显著高于W1处理,获得了较高的籽粒产量和水分利用效率,且干物质积累与分配、籽粒产量和水分利用效率在两年中结果趋势一致.在150株m-2密度下,0～140 cm土层平均土壤相对含水量拔节后7 d和开花后7 d均为75%和75%,是本试验条件下节水高产的最佳处理.
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