关键词: 冻融栓塞, 冻害疲劳, 导管直径, 栓塞面积

Abstract:

Objective: This study aims to explore frost fatigue and its relationships with freeze-thaw-induced embolism and xylem anatomical structure in different trees from temperate zones, which can improve knowledge of winter plant hydraulics and provide new theoretical basis for the selection of suitable tree species for afforestation in temperate and boreal regions. Method: Six common temperate trees [Acer truncatum, I-101 (Populus alba) × 84K (P. alba× P. glandulosa), Liriodendron chinense, Salix matsudana, Betula platyphylla, and Platanus orientalis] were used as study materials and their branches were collected in January of winter. A modified Cavitron freezing centrifuge was utilized for freeze-thaw treatments and constructed native vulnerability curves (NVCs) and frost fatigue vulnerability curves (FFVCs). The embolic areas (EAs) of these two vulnerability curves per species were calculated to assess the degree of frost fatigue (DFF). For each of species, the native percentage loss of hydraulic conductivity (NPLC), i.e., the degree of freeze-thaw-induced embolism, was determined by a low-pressure flow meter (LPFM) and xylem anatomical structure traits were measured, such as vessel diameter (D), vessel density (V_D), vessel lumen fraction (F), intervessel contact fraction (F_C), and wood density (WD). Result: After undergoing freeze-thaw treatment, the resistance of xylem embolism decreased for all tree species and frost fatigue occurred. For all tree species, the frost fatigue vulnerability curves were double S-shaped compared to the S-shape of the native vulnerability curves. Compared with the embolism area of NVC, the embolism area of FFVC of A. truncatum was slightly reduced with no significant difference, while the embolism areas of FFVCs of the other five tree species were significantly reduced. The degree of frost fatigue showed pronounced interspecific differences and ranked as I-101 (P. alba)×84K (P. alba×P. glandulosa) > S. matsudana > P. orientalis > L. chinense > B. platyphylla > A. truncatum. There were significant differences in the degree of freeze-thaw-induced embolism and xylem anatomical structure traits among different tree species. The degree of frost fatigue was significantly positively correlated with the degree of embolism induced by freeze-thaw, and only with vessel diameter in the xylem anatomical structure traits. The degree of freeze-thaw-induced embolism was also significantly positively correlated with vessel diameter. Conclusion: There are obvious differences in frost fatigue among the six tree species. A. truncatum has strong resistance to frost fatigue with the lowest degree of frost fatigue and is “resilient species”. The other five species have high vulnerability to frost fatigue and are “weakened species”. Tree species with wider vessel have higher degrees of freeze-thaw-induced embolism and frost fatigue. Vessel diameter thus is the key structural trait that determines the degree of freeze-thaw-induced embolism and frost fatigue of trees. Tree species with narrow conduits in the xylem are more resistant to freeze-thaw-induced embolism and frost fatigue, which would favor their survival and distribution in cold environments in temperate and boreal regions.

Key words: freeze-thaw-induced embolism, frost fatigue, vessel diameter, embolism area