Abstract:

Aims Pressure-volume traits of leaf and fine roots play a crucial role in the hydraulic architecture of trees, but the differences between leaf and root turgor loss point (TLP) and their relationship with the stomatal closure point (Ψ_close) among tree species are not fully understood. Moreover, the potential relationships between leaf and root morphological characteristics, non-structural carbohydrate (NSC) contents and turgor loss traits is not clear across species. This study in order to address this issue and provide a theoretical basis for the selection of tree species for afforestation in the loess hilly region.

Methods Five coniferous tree species and seven broadleaf tree species commonly occurring in the loess hilly region were selected, to analyze the differences in their Ψ_close, TLP and NSC contents of leaves and fine roots as well as the relationship between leaf and fine root morphology traits, NSC content and TLP.

Important findings The TLP of fine roots of coniferous tree species was 47.86% significantly lower than broadleaf species, while Ψ_close was 39.04% significantly higher than broadleaf species. The Ψ_close of coniferous species is 48.06%, 33.82% significantly higher than TLP of leaves and fine roots but the TLP of leaves and fine roots in broadleaf species was 19.83%, 37.70% higher than Ψ_close. The water capacity of leaves and fine roots of coniferous tree species was significantly lower than broadleaf species, with the elastic modulus and the soluble sugar content were significantly higher than broadleaf species. Besides, the leaf TLP of all tree species was significantly lower than that of fine roots. Correlation analysis showed that significant positive correlations existed between specific leaf area and leaf TLP, specific root length and fine root TLP, as well as leaf TLP and fine root TLP for all tree species. The above results show that coniferous species had stronger turgor pressure maintenance ability and greater stomatal sensitivity, which makes it easier to maintain water balance under drought conditions. In contrast, broadleaf species can maintain stomatal conductance even when the water potential dropped below TLP, showing stronger tolerance to stomatal dehydration, but more susceptible to hydraulic failure. The results of this study also suggests that there were differences in the relationships of turgor loss points and stomatal closure points between coniferous and broadleaf tree species. This study reveals the differences in the pressure-volume traits and stomatal regulation of leaves and fine roots among different tree species, and clarifies the species-specific differences in drought adaptability, which could help to predict the selection of afforestation tree species in the context of global change.

Key words: turgor loss point, stomatal regulation, fine root, leaf, non-structural carbohydrate