关键词: 抽条, 柿树, 水力性状, 解剖结构, 非结构性碳水化合物

Abstract: By analyzing the differences in water status and nonstructural carbohydrate (NSC) content of persimmon trees of different ages in winter and spring, we explored the physiological mechanisms underlying the worse shoot shriveling of young persimmon trees, which would provide theoretical basis for reducing the shoot shriveling harm in production practice. We measured hydraulic vulnerability (P₅₀) and anatomical structure of one and five-year-old persimmon tree (Diospyros kaki var. zaoshuzhushi), and compared the water status and NSC content of branches of both age-classes in winter and spring (October 2023-April 2024). We conducted a base-cutting test during shoot shriveling-prone periods (March 2024), to measure shoot shriveling rates. Results showed that the P₅₀ of branches of one and five-year-old persimmon trees were increased by 0.19 and 0.24 MPa from October to December, respectively. The branch hydraulic safety of one-year-old trees was lower than that of five-year-old ones. Wood density, vessel wall thickness, and vessel collapse-resistance index of one-year-old trees were significantly lower than those of five-year-old ones, while the lenticel density and vessel diameter of branches of one-year-old trees were significantly higher than those of five-year-old ones. During most of the time in winter and spring, the pre-dawn water potential of branches, water content of the phloem and xylem, cell vitality of the phloem and xylem, and the xylem NSC contents of one-year-old trees were significantly lower than those of five-year-old ones. However, the branch percentage loss of conductivity (PLC) and relative electric conductivity of the one-year-old trees were significantly higher than those of the five-year-old ones. The water loss rate of the one-year-old trees in March was significantly higher than that of the five-year-old ones. The shoot shriveling rates of the one- and five-year-old persimmon trees were 56.0% and 20.8%, respectively. In the base-cutting test, the branch pre-dawn water potential and the water content in phloem and xylem of the cutting trees were lower, while their branch PLC and relative electric conductivity were higher, compared to non-cutting trees with the same age. Compared to five-year-old base-cutting trees, one-year-old base-cutting trees had lower branch pre-dawn water potential and water content in the phloem and xylem, but higher PLC and relative electric conductivity. Overall, compared with five-year-old ones, one-year-old persimmon trees have a weaker ability to resist embolism in branches, resulting in lower capacity of maintaining long-distance water transport and faster water loss from branches. Less water storage in the tree body, leading to worse water condition of branches in winter and spring, further caused severe shoot shriveling of the one-year-old persimmon trees.

Key words: shoot shriveling, persimmon tree, hydraulic trait, anatomical structure, nonstructural carbohydrate