Differences in water use efficiency of Abies holophylla seedlings from seven provenances under water stress

By taking current-year seedlings of Abies holophylla from seven provenances in one of natural distribution areas (i.e., eastern mountainous areas of Liaoning Province) as study objects, we studied long-term water use efficiency (WUEL), instantaneous water use efficiency (WUEI), stable carbon isotope composition (δ13C) of A. holophylla seedlings, and their relationships under three water treatments (sufficient water supply, slight water stress and severe water stress) in greenhouse, in order to reveal the differences in water use efficiency of A. holophylla seedlings among provenances and the mechanisms underlying physiological response of A. holophylla seedlings to water stress. The results showed that with the increase of water stress, WUEL of seedlings from seven provenances increased, and the difference of WUEL among provenances was significant (P0.05) only under severe water stress treatment, but there was no significant difference among provenances under sufficient water supply and slight water stress treatment. WUEI and leaf δ13C also increased, and the differences of WUEI and leaf δ13C among provenances were very significant (P0.01) under three water treatments. The difference of WUEL among different water treatments reached significant (P0.05) or very significant level (P0.01), and the difference of WUEI and leaf δ13C among different water treatments all reached very significant level (P0.01). Leaf δ13C and WUEL of seedlings under each water treatment showed a positive correlation, and this correlation became closer and closer with the increase of water stress. Therefore, leaf δ13C can be the effective index for selecting provenances of A. holophylla with high water use efficiency.