Abstract:

Stable carbon isotope discrimination(Δ¹³C)is a good predictions of water use efficiency(WUE),and is already applied in crop breeding programs,and some high WUE cultivars have been selected with the method.At present,the study on estimation of the WUE of different poplar clones by Δ¹³C is a few.In order to probe the WUE changes on different temporal scales during growth process of field-cultured poplar,and the relationship between Δ¹³C and growth,the WUE of 7 clones were respectively determined by Δ¹³C in leaves,branches and stems(respectively abbreviate to Δ¹³C _leaf,Δ¹³C_branchand Δ¹³C_stem)as well as gas exchange method.The results indicated that the Δ¹³C_leaf,Δ¹³C_branchand Δ¹³C_stemsignificantly and orderly decreased as well as the corresponding WUEs increased orderly.The estimations on WUE for 7 clones by gas exchange method were approximately consistent with the results derived from Δ¹³C_leaf,but they did not agree with the outcomes based on Δ¹³C_branch and Δ¹³C_stem, which were consistent with each other.Because the Δ¹³C_stem reflects integrated WUE on a longer period than the Δ¹³C_leaf and Δ¹³C_branch,the Δ¹³C_stem was considered as a good index for WUE determination at whole plant level.The correlation analysis between the Δ¹³C in different organs and growth showed that there was no correlation between Δ¹³C_leaf and growth,but both Δ¹³C_branch and Δ¹³C_stem had a significantly positive correlation with growth,so the Δ¹³C_branch and Δ¹³C_stem have a potential application to determine growth of poplar besides their application on WUE.

Key words: poplar;water use efficiency(WUE);stable carbon isotope discrimination(&Delta, ¹³C);growth