The xylem functional traits of eight subtropical tree species is closely related to the intervessel pits ultrastructure

Key message There is a trade-off between plant water transport safety and efficiency, which may be linked to pit ultrastructure traits. Drought-induced embolism is one of the most important causes of plant death, and there is a close relationship between the formation and spreading of embolism and xylem structure. However, many previous studies on xylem structure lack detailed observation in intervessel pits, especially pit membranes, which have important roles in water transport and embolism spreading for angiosperms. Here, we selected eight species from subtropical forests and studied their xylem structure and functional traits. The results showed that there was a trade-off between hydraulic transport safety and efficiency in eight species, which may be related to their xylem structure. The diameter of pit aperture and pit membrane, as well as the pit membrane thickness, showed significant relationships with xylem embolism resistance, indicating that the ultrastructure of intervessel pits was a good predictor for xylem safety. With detailed observation in pits ultrastructure, this study helps to elucidate the response mechanism of trees to drought and predict forest distribution and succession.