Effects of Plant Density and Soil Moisture on Photosynthetic Characteristics of Flag Leaf and Accumulation and Distribution of Dry Matter in Wheat

Water shortage is one of the major problems in wheat (Triticum aestivum L.) production in northern plain in China, and water-saving technique is of great importance in wheat cultivation in this area. A water-controlled irrigation strategy based on measuring soil moisture at jointing and anthesis stages (SMJ+SMA) was adopted in a 2-year field experiment in Shandong Province, China from October 2008 to June 2010, using the famous commercial wheat cultivar Jimai 22. The dynamics of photosynthetic parameters and dry matter accumulation were determined during grain filling period. In the 2008–2009 growing season, 3 irrigation treatments were designed under the plant densities of 150 (M1) and 225 seedlings m−2 (M2), whose SMJ+SMA percentages were 65%+60% (W0), 75%+75% (W1), and 75%+75% at 7 d after jointing or anthesis (W2). In the 2009–2010 growing season, the irrigation treatments were conducted under only M1 density because M1 showed higher yield and water use efficiency (WUE) than M2 density in last season. The SMJ+SMA percentages in the 3 irrigation treatments of 2009–2010 were adjusted to 75%+60% (W'0), 85%+75% (W'1), and 85%+75% at 7 d after jointing or anthesis (W'2). Under the same irrigation condition, the maximal photochemical efficiency of PSII (Fv/Fm) and actual photochemical efficiency of PSII (ϕPSII) in M1 treatment were higher than those in M2 treatment from middle to late grain-filling stage, and the dry matter accumulation amount after anthesis and dry matter translocation to grains in M1 treatment were significantly higher than those in M2 treatment. Under the same plant density condition, the Fv/Fm and ϕPSII values were significantly higher in W2 treatment than in W1 treatment from middle to late grain-filling stage; and the photosynthetic rate (Pn), evapotranspiration (Tr), leaf WUE, and stomatal conductance (Gs) were higher in W'2 treatment than in W'1 treatment. The management of soil moisture to 75–85% at 7 d after jointing or anthesis showed the largest dry matter accumulation amount after anthesis and its contribution to grains, grain yield, and WUE under the M1 density. In the practical point of view, plant density of 150 m−2 and the SMJ+SMA percentages of 75%+75% at 7 d after jointing or anthesis are proposed in water-saving wheat production with environment similar to this experiment.

摘要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(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(ΦPSII)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ΦPSII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, 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。