Abstract: 【Objective】 To investigate the influences of water stress at different growth stages on the growth and yields of winter wheat, field experiments were conducted under a rainout shelter during two seasons of 2012-2013 and 2013-2014. The dynamic changes of several eco-physical characteristics of wheat growth were measured and compared, including height, leaf area index, phenology, biomass, and yield. 【Method】 The whole growth season of wheat was divided into five growing stages (wintering, greening, jointing, heading, and grain filling). Water stress occurred at two continuous stages, while irrigations were applied at other stages, which resulted in four different levels of stress period (D1-D4). Two irrigation levels of 40 mm (I1) and 80 mm (I2) were applied. A total of eight treatments, with three replicates for each, followed a split-plot experiment design. An extra control treatment with irrigation at all five stages was arranged beside.【Result】The results showed that normal growth and development of wheat could be obviously influenced by continuous water stress given at vegetative stages. The height, LAI and biomass were the worst for all treatments, when water stress occurred at the stages of wintering and greening. However, the negative influences on wheat growth were not notable when water stress occurred after jointing stage. The average growth rate of height and LAI after jointing was about ten times as that before jointing. There were no notable differences of biomass between all of the treatments until the jointing stage. The biomass values of treatments with water stresses at wintering and greening stages were remarkably lower than other treatments. The irrigation later could not recover these serious biomass losses. Water stress could shorten the whole growth season of wheat, with a maximal 5-day advancing of maturation. At the same irrigation level, the heading and flowering stages could be delayed for 1-3 days for different levels of stress period. For the same irrigation level, relatively higher numbers of productive ears and seeds per ear could be obtained when water stress occurred at the heading and grain filling stages, but with a lower thousand-kernel weight. On the contrary, a relatively higher thousand-kernel weight could be achieved when irrigation was applied at the heading and grain filling stages, but with lower numbers of productive ears and seeds per ear. For irrigation levels of I1 and I2, yields were the lowest when water stress occurred at wintering and greening stages, which was only 42% of the control treatment. However, the treatments with the highest yield were different for different irrigation levels. For I1, it was the treatment with water stress at jointing and heading stages that had the highest yield, or about 63% of the control treatment. For I2, it was the treatment with water stress at greening and jointing stages, which had a yield of about 75% of the control treatment. 【Conclusion】There was a clear interaction between the intensity and occurring stage of water stress. In general, the greening and filling stages were the critical periods of water demand for winter wheat. Reasonable irrigation managements are needed at these two growth stages to guarantee a higher yield of winter wheat in arid region.

Key words: winter wheat, water stress, growth stage, phenology, biomass, yield