Effect of Water Deficit at Different Growth Stages on Root Efficiency and Drought Tolerance in Late Growing Stage of Winter Wheat

A pot experiment was conducted to clarify the effect of water deficit at different growth stages on root efficiency and water use efficiency of winter wheat.Plants were subjected to three water deficit stages: over-wintering-jointing stage,returning green-jointing stage,jointing-heading stage,plants were maintained at 45%~50% FWC(field water capacity) at every stage.After water deficit treatment terminated,plants were maintained at 70% FWC.The control plants(CK) were maintained at 70% FWC in the experimental period.The results showed that water deficit treatments of returning green-jointing stage improved significantly root efficiency and water use efficiency of winter wheat.Water deficit treatments of over-wintering-jointing stage and jointing-heading stage improved significantly root efficiency of winter wheat and reduced significantly water consumption,but water use efficiency was unaffected due to reducing grain yield.The values of chlorophyll fluorescence parameters,i.e.,effective PSⅡ quantum yield,apparent rate of photosynthetic electron transport,coefficient of photochemical quenching and coefficient of non-photochemical quenching,were significantly higher in three water deficit treatments than the control 5 days after withholding water at anthesis.This means that water deficit treatments improved drought tolerance ability of wheat,resulting in improved photosynthetic capability.