Effects of water stress on photosynthetic characteristics, dry matter translocation and WUE in two winter wheat genotypes

Determining the effects of a water deficit during periods of vegetative growth on photosynthetic traits and grain yield will provide a reasonable strategy for water-saving management of winter wheat (Triticum aestivum L.) and exploited photosynthetic traits for the selection of drought tolerant winter wheat genotypes. A mobile rain shelter experiment was conducted using winter wheat cultivar to assess the effects of different levels of water stress on photosynthetic characteristics, dry matter translocation and water use efficiency (WUE) in the Shijiazhuang 8 (drought resistant) and Yanmai 20 (drought sensitive) cultivars at different growth stages. Three winter wheat growing stages were selected for assessment at follows: recovering-jointing, jointing-flowering and grain-filling, and the effects of four levels of soil water which were selected based on field capacity, on plants from seeding to mature stage were examined by controlling the irrigation as follows: 40–45% (severe stress), 55–60% (moderate stress), 65–70% (mild stress) and 75–80% (full irrigation) The results indicated that mild stress during the recovering-jointing stage improved the canopy structure prior to anthesis and maintained high canopy photosynthesis after anthesis, thus increasing winter wheat yields. Mild stress during all of the growth stages improved the distribution of assimilate to the grain prior to anthesis and increased the yield. Although moderate stress during all growth stages could improve dry matter translocation, the resulting yield was not high, as the accumulation of dry matter decreased after anthesis. Therefore, mild soil water stress can improve grain yields and WUE. Shijiazhuang 8 displayed a higher grain yield and WUE than Yanmai 20 under drought stress, and throughout the different stages of growth, the leaves exhibited a lower net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration (E) under drought stress. Furthermore, Shijiazhuang 8 which maintained relatively higher, Pn, Gs and E under water stress, maintained higher values of WUE than Yanmai 20. Under the severe stress treatments, some varieties showed an increase in the concentration of intercellular CO2 (Ci), indicating an inhibition of photosynthetic activity due to non-stomatal effects. Overall, we conclude that the genotypic differences in the photosynthetic response could be useful for mapping the photosynthetic traits that promote tolerance to drought. We recommend that mild water stress (65–70% water field capacity) be considered for irrigation scheduling in winter wheat under conditions of water limitation.