Gas exchange, photochemical efficiency, and leaf water potential in three Salix species

Abstract

Gas exchange, photochemical efficiency, and leaf water potential (Ψ1) of Salix matsudana (non-indigenous species), S. microstachya and S. gordejevii (indigenous species) were studied in Hunshandak Sandland, China. Ψ1 of all the three species decreased from 06: 00 to 12:00, and increased afterwards. S. matsudana showed higher values of Ψ1 than others. Net photosynthetic rate (PN) and stomatal conductance (gs) of S. matsudana were the lowest among all, with the maximum PN at 10:00 being 75 % of that of S. gordejevii. Compared with the indigenous species, the non-indigenous S. matsudana had also lower transpiration rate (E) and water use efficiency (WUE). The values of Fv/Fm in all the species were lower from 06:00 to 14:00 than those after 14:00, indicating an obvious depression in photochemical efficiency of photosystem 2 in both non-indigenous and native species. However, it was much more depressed in S. matsudana, the non-indigenous tree. P N was positively correlated to gs and negatively related to Ψ1. The relationship between gs and vapour pressure difference (VPD) was exponential, while negative linear correlation was found between gs and Ψ1.