[Effects of irrigation regimes on photosynthesis, water use efficiency and grain yield in winter wheat].

The effects of different irrigation regimes on photosynthesis, plant growth, water use efficiency (WUE), and grain yield in winter wheat were examined in a common garden with rainout shelter during 2013-2014 and 2014-2015 growing seasons. The experiment consisted of two irrigation timings, jointing stage (J) and anthesis (F), and three irrigation levels, 0, 37.5 and 75 mm, which generated nine irrigation combinations, i.e. JF, JF, JF, JF, JF, JF, JF, JF and JF. All plots received 75 mm irrigation at grain filling stage. The results showed that water stress at jointing stage significantly reduced leaf area after jointing stage and the net photosynthetic rate (P) at anthesis. Post-anthesis flag leaf P was significantly affected by irrigation at anthesis. Water stress at jointing stage followed irrigation at anthesis or that at anthesis followed irrigation at grain filling stage increased dry matter accumulation of wheat plants. Higher amount of irrigation at jointing stage led to higher water consumption in the entire growing period. High amount of irrigation during the entire growing period resulted in high water consumption and grain yield with an exception of JF treatment. Among all the treatments, the JF treatment had superior grain yield and WUE. Sufficient water supply at anthesis resulted in high flag leaf P after flowering in JF. Irrigation at anthesis for JF enhanced wheat dry matter accumulation and kernel numbers per spike, and consequently high yield. Small amount of irrigation at jointing stage reduced wheat water consumption at middle and late growth stages. The wheat WUE in treatments with small amount of irrigation at jointing stage (JF) was higher than in other treatments. In this study, JF was the best irrigation regime for winter wheat.