Abstract:In this paper, we set a full irrigation test for winter wheat at different growth stages from the getting-up to the grain filling, that is, the full irrigating treatment is carried out in the getting-up stage (T1), the getting-up and jointing stages (T2), and the earing-up and grain filling stages (T3), respectively. The whole process from soil water saturation to drought in natural state is simulated, and the effects of persistent water stress on photosynthesis and yield of winter wheat are studied by taking full irrigating treatment at each growth stage from the getting-up to the filling stages as a control (CK）, so as to provide a reference for selecting a good irrigation timing in the spring farmland of winter wheat. The results show that the chlorophyll content, net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr) and intercellular CO2 concentration (Ci) of flag leaves of wheat all decrease under persistent water stress, and the diurnal variation peak of photosynthesis appears earlier to different extents. At the three stages of T1, T2 and T3, the Tr and Ci of wheat treated by sufficient irrigation at T1, T2 and T3 are significantly different from those of CK at different growing stages, but there is no significant difference between the treatments of T1, T2 and T3 at the mid-filling stage. The chlorophyll content, Pn and Gs are reduced more significantly in the treatment of SPAD at the grain-filling than in the treatment of continuous water stress only at T2, even after the treatment of continuous water stress at T3. Winter wheat is subjected to persistent water stress at T3, which could result in the most obvious decrease in spike number and grain number per spike, and has the greatest effect on the yield of winter wheat.