Abstract:Water shortage is a main limited factor to agriculture and crop production, so it is important to improve the crop water use efficiency (WUE) in limited water resource. The leaf WUE is the physiological foundation for improving field water use efficiency. In early researches only one or a few wheat cultivars were employed to analyze the relationship between WUE and single or a few physiological traits, or only the daily variation regularity of leaf WUE and relevant physiological traits studied. 19 wheat cultivars, possessing different drought-resistance, from different winter wheat growth regions in China, were employed in this drought-resistance trial,with no irrigation during whole growth period, for analyzing the correlation between leaf WUE and other 11 traits of wheat flag leaf, including photosynthetic rate(Pn), transpiration rate(Tr), ... ...