Discrimination of water use efficiency (WUE) among three Populus deltoids clones

Populus deltoids is a fast growing and high water-consuming species.It is necessary to choose clones with high water use efficiency when they are introduced to China.In our test,long-term water use efficiency (WUEL),instantaneous water use efficiency (WUEi),foliar carbon isotope composition (δ13C),photosynthesis,stomatal density and stomatal conductance(Gs) of three P.deltoids clones(DN2,P.deltoides×P.nigra;R-270,P.deltoides×P.nigra;NE-19,P.nigra×(P.deltoides×P.nigra)) were studied under different water treatments.The results showed that significant differences in these parameters were detected among three clones,indicating the variation of water use efficiency among three clones.NE-19 was the best clone,with the highest WUEL,WUEi,δ13 C and net photosynthetic rate(Pn) and the lowest stomatal density and Gs.Therefore,we make a conclusion that stomatal density and conductance are the major factors which could lead to the variation of Pn and WUE i and in turn affect WUEL and δ13C.δ13 C could be a good indicator to evaluate the WUEL of clones,which was correlated with WUEL under sufficient water supply;however,the correlation decreased under water stress.ERECTA gene is the first gene which could regulate plant transpiration efficiency in Arabidopsis.A cDNA clone,designated PdERECTA,was isolated from P.deltoids.RT-PCR indicated that PdERECTA gene may have the similar function in P.deltoids.