Comparative study on photosynthesis and water physiology of polymorphic leaves of Populus euphratica

The photosynthetic characteristics，stomatal characteristics and water physiology of dentate broadovate leaves and lanceolate leaves from Populus euphratica were studied in this paper. The results showed that Pn of dentate broadovate leaves was higher than that of lanceolate leaves. Under normal conditions, the light compensation points of dentate broadovate leaves and lanceolate leaves were 60 and 75 μmol/(m2•s) respectively, the light saturation point of both was above 1 800 μmol/(m2•s). Both of them could not reach the light saturation point under normal conditions. Tr, stomatal density and size of dentate broadovate leaves were higher than that of lanceolate leaves, while the stomatal opening rate was lower than that of lanceolate leaves. Ψ100, Ψ0 and the difference of the two values of dentate broadovate leaves were lower than that of lanceolate leaves. The ε values of dentate broadovate leaves and lanceolate leaves were 8.432 4 and 2.359 7 respectively. The average hydraulic conductivity of branches with dentate broadovate leaves and lanceolate leaves was 6.61×10-5 and 5.19×10-5 kg/(s•MPa); and the reduction of hydraulic conductivity of dentate broadovate leaves and lanceolate leaves was 0.06×10-5 and 1.88×10-5 kg/(s•MPa) respectively after drought stress, this indicated that the hydraulic conductivity of branches with dentate broadovate leaves was relatively stable in dry environments. The study shows that, the light energy efficiency and water stress tolerance ability of dentate broadovate leaves are higher than that of lanceolate leaves, maybe these changes are the results of leaves of P. euphratica to adapt to the environmental stress during their development.