Comparison study on water use efficiency of wheat flag leaf

44 wild species and cultivars were planted under irrigated and dryland field condition. LCA-3 model photosynthesis apparatus was employed to measure flag leaf WUE. The results show that WUE of diploid and tetraploid increases as the wild species became cultivated species. WUE of flag leaf increases as the chromosome ploid increases (2n→4n→6n) in the wheat evolution. Among modern cultivars, WUE of most irrigated varieties is higher than that of dryland varieties.