【目的】分析板栗童期向成年期转变过程中叶片形态、结构的变化规律及差异,探明板栗的生长阶段转变期及叶片变化特征,为采用外源调控技术促进板栗提早开花结实提供理论依据。【方法】以河北省迁西地区板栗主栽品种‘燕山早丰’(Castanea mollissima ‘Yanshanzaofeng’)1、3、6和10 a树龄的实生幼树叶片为试验材料,于2023年8月下旬使用叶面积仪测定叶片形态指标;使用指甲油印迹法观察叶片气孔结构;同时制作叶片、叶柄的石蜡切片,并利用光学显微镜观察拍照,使用Image J软件测定叶片及叶柄解剖结构指标。【结果】①不同树龄板栗之间叶片的长度和宽度、叶面积和叶形指数差异不显著,但叶柄长度、叶片栅栏组织厚度、海绵组织厚度和叶片厚度大小依次为10 a、6 a、3 a、1 a;②叶片结构指标在1与3 a树龄间存在差异,但不显著,而3 a与6、10 a树龄间气孔密度、下表皮厚度和上表皮厚度、组织结构紧密度、组织结构疏松度、栅海比以及木质部厚度、韧皮部厚度、木质部与韧皮部之比、维管束比例、导管直径和导管数量等各指标存在显著差异。叶片上表皮厚度、栅海比随树龄增加而增大,而组织结构疏松度和气孔密度随树龄增加而降低;③叶片与叶柄的形态指标间和结构指标间均存在显著的相关性,而结构指标间的相关性更强(P<0.001);④主成分分析结果显示,叶形指数和叶面积、叶柄长度、叶柄粗度等形态指标以及叶片气孔密度、上表皮厚度、下表皮厚度、栅栏组织厚度、叶片厚度、栅海比、叶柄木质部厚度、导管数量和叶柄韧皮部厚度等结构指标贡献率较大。【结论】3 a树龄为板栗‘燕山早丰’阶段转变期,叶柄长度、叶柄粗度等形态指标可作为判定其实生树通过童期的参考指标,建议对3 a树龄板栗采用外源调控技术促进其提早开花结实。

【Objective】This study aims to analyze the changing patterns and differences in leaf morphology and anatomical structure during the transition from the juvenile to the adult phase in chestnut (Castanea mollissima) trees, to identify the critical stage transition periods as well as the characteristics of leaf changes, and to provide a theoretical basis for promoting early flowering and fruiting through exogenous regulation techniques.【Method】Leaf samples were collected from seedling trees of the dominant chestnut cultivar ‘Yanshanzaofeng’ in Qianxi County, Hebei Province, China, including one-year-old (1 a), three-year-old (3 a), six-year-old (6 a) and ten-year-old (10 a) trees. In late August, leave area were employed to measure leaf morphological traits. At the same time, the nail polish impression method was used to observe the stomatal structure of the leaves. Paraffin sections of leaves and petioles were prepared, observed, and photographed under an optical microscope. Meanwhile, leaf anatomical structure indicators and petiole anatomical structure indicators were measured using Image J software.【Result】(1) No significant differences are found in leaf length, leaf width, leaf area, or leaf shape index among Chinese chestnut trees of different ages. However, petiole length, palisade tissue thickness, spongy tissue thickness, and leaf thickness follow a pattern of ten-year-old trees > six-year-old trees > three-year-old trees > one-year-old trees. (2) Differences in leaf structure indices between one-year-old and three-year-old trees are observed but are not significant. Nevertheless, significant differences are observed in various indices, such as stomatal density, lower epidermal thickness, upper epidermal thickness, tissue structure tightness, tissue structure porosity, ratio of palisade to spongy tissue thickness, xylem thickness, phloem thickness, ratio of xylem to phloem thickness, vascular bundle ratio, vessel diameter, and number of vessels, between three-year-old trees and both six-year-old and ten-year-old trees. Upper epidermal thickness and ratio of palisade to spongy tissue thickness increase with tree age, whereas tissue structure porosity and stomatal density decrease with tree age. (3) Significant correlations are found both among the morphological indices and among the anatomical indices of leaves and petioles. Moreover, the correlations among the anatomical indices are stronger (P < 0.001). (4) The results of principal component analysis indicate that morphological indices such as leaf shape index, leaf area, petiole length, and petiole thickness, along with anatomical indices such as stomatal density, upper epidermal thickness, lower epidermal thickness, palisade tissue thickness, leaf thickness, ratio of palisade to spongy tissue thickness, petiole xylem thickness, vessel number, and petiole phloem thickness, have relatively high contribution rates.【Conclusion】The three-year-old stage represents the growth stage transition period of the‘Yanshanzaofeng’cultivar of Chinese chestnut. Morphological indices such as petiole length and petiole thickness can serve as reference indicators for determining whether seedling trees have passed the juvenile phase. It is recommended that exogenous regulation techniques be applied to three-year-old trees to promote early flowering and fruiting.