Abstract: [Objective] Drought has become a key factor affecting plant growth in the world. Hence, it is necessary to study the xylem embolism and refilling. The aim of this study was to explore the relationship between hydraulic traits and embolism refilling in the xylem of six tree species, to elucidate the influence of xylem hydraulic traits on the embolism refilling, and to provide theoretical evidence for screening drought-resistant tree species.[Method] Six well-growing tree species, Robinia pseudoacacia, Hippophae rhamnoides, Ulmus pumila, Acer truncatum, Salix matsudana and Corylus heterophylla were studied. Cochard Cavitron centrifuge was used to induce xylem embolism of one-year-old twigs when percentage loss of conductivity was higher than 95%. The "vulnerability curves" of six tree species were plotted to obtain the mean value of P₅₀. The recovery level of different periods (20, 40, 60, 80, 100 min) was measured by Low Pressure Flow Meter with multi-channels and staining methods. At the same time, the hydraulic diameter, pre-dawn water potential of xylem and natural percentage loss of conductivity (NPLC) were measured.[Result] 1) The order of the average P₅₀ values of the six species was R. pseudoacacia > U. pumila > H. rhamnoides > S. matsudana > C. heterophylla > A. truncatum, and A. truncatum was the most drought-tolerant tree species; 2) The recovery level of the xylem embolism by staining method was consistent with embolism recovery level by Low Pressure Flow Meter. The regression equation was y=1.047x-7.567, R²=0.863. The LPFM method can completely reflect the recovery level of the embolism branches in different time periods; 3) The xylem embolism recovery capacity of the six tree species was ranked as follows:R. pseudoacacia > U. pumila > H. rhamnoides > S. matsudana > C. heterophylla > A. truncatum. This implies that tree species with the high recovery ability of xylem embolism can quickly restore the function of transporting water when the plants are resupplied with water. The results showed that the order of the abilities of xylem embolism refilling was completely consistent with the order of embolism vulnerabilities. The ability of embolism refilling increased with embolism vulnerability (R²=0.980). Regression analysis indicated that the ability of embolism refilling of the six tree species was strongly correlated with hydraulic diameter, pre-dawn water potential of xylem, NPLC, with values of R² of 0.868, 0.740, 0.741, respectively.[Conclusion] The hydraulic traits of xylem were closely related to the refilling ability of xylem embolism. In particular, there was a strong positive correlation among P₅₀, hydraulic diameter and the ability to recover from embolism. Therefore, P₅₀ and hydraulic diameter were the main influencing factors for embolism refilling.

Key words: embolism refilling, hydraulic traits of xylem, embolism vulnerability, hydraulic diameter