【目的】从生理和组织结构角度分析5个山乌桕(Triadica cochinchinensis)家系叶片着色的关键因子,探讨不同遗传材料在不同时期叶片色素含量的变化及其呈色响应,为山乌桕景观型优良品种的选育提供理论依据。【方法】 以树高50 cm的5个山乌桕家系(SD4—8,SD12)为研究材料,在自然条件下观察S1(2021-10-29)、S2(2021-11-05)、S3(2021-11-12)、S4(2021-11-19)、S5(2021-11-26)、S6(2021-12-03)6个时期的叶色变化,定期测定参试植株的叶色参数(L^*、a^*、b^*)、色素(叶绿素、胡萝卜素、花色苷)含量、解剖结构(上下表皮、栅栏组织、海绵组织)等,分析山乌桕叶色动态变化并进行家系优选。【结果】 ①在S1—S6时期山乌桕各家系叶片呈现的颜色主要为淡绿—深棕黄—棕黄—朱红—大红,观赏佳期集中在S5—S6时期,其中SD8是观赏价值最高的山乌桕家系,且从开始变色(S2)到完全落叶的色叶期长达37 d。②山乌桕各家系叶片叶色参数a^*呈直线上升趋势,而L^*和b^*的变化规律不尽相同。具体而言,叶片越绿,a^*越小;叶片越红,a^*越大;a^*为5个山乌桕家系叶色变红的代表性参数。③在整个观测期中所有山乌桕家系的叶绿素、类胡萝卜素含量呈现下降趋势,而花色苷含量与之呈相反规律,各色素含量均在S3时变化幅度达到最大。其中叶色由绿转红主要是色素含量比例分配变化,S3前主要以叶绿素含量为主,为绿叶期;S3后主要以花色苷含量为主,为红叶期。④山乌桕叶色由绿变红过程中,各家系叶片厚度均表现为转色前大于转色后,其中SD4家系的叶片厚度最大降幅达到29.17%,显著高于其他家系(P<0.05);所有家系的上表皮厚度均大于下表皮厚度,其中转色前SD6家系的上表皮厚度显著小于其他家系(P<0.05),转色后SD6家系的上下表皮厚度在所有家系中占比最大,且与其余家系差异显著(P<0.05);海绵组织厚度均大于栅栏组织厚度,转色前后SD4和SD6家系的海绵组织厚度变化幅度存在大小最值,变化幅度分别为30.59%、0.87%,SD8的栅栏组织厚度与其余家系有显著性差异(P<0.05),最大变化幅度为29.92%。⑤转色后大部分山乌桕家系的叶片组织结构表明叶片厚度、栅栏组织和海绵组织厚度的减少可积累花色苷含量,使山乌桕叶片变红,且叶片组织内未出现颗粒和蜡质等明显变异附着物,没有出现较大的气室。【结论】山乌桕的叶色变化主要受色素的动态变化影响,花色苷是导致叶片转红的主要因素。在研究的5个山乌桕家系中,SD8家系表现出最为优异的叶色变化,其观赏价值较高,特别适用于景观绿化。该研究为山乌桕品种选择及其观赏价值的评估提供了理论支持。

【Objective】This study aims to explore the changes in leaf pigment content and color response of different genetic materials over various periods and to analyze the key factors influencing leaf coloration in five families of Triadica cochinchinensis from physiological and tissue structural perspectives. The findings are expected to provide a theoretical basis for selecting superior landscape varieties of T. cochinchinensis.【Method】 Five families of T. cochinchinensis with a height of 50 cm were selected as research materials. The leaf color changes of six time points (S1. 2021-10-29; S2. 2021-11-05; S3.2021-11-12; S4. 2021-11-19; S5. 2021-11-26; S6: 2021-12-03) were observed under natural conditions. Leaf color parameters (L^*, a^*, b^*), pigment content (chlorophyll, carotene, anthocyanin), and anatomical structure (upper and lower epidermis, palisade tissue, spongy tissue) were measured regularly. The dynamic changes in leaf color and genealogy selection of T. cochinchinensis were analyzed.【Result】(1)The leaf color of each T. cochinchinensis genealogy during the S1—S6 period primarily transitioned from light green to dark brownish yellow, then to reddish brown, and finally to bright red, with the ornamental period concentrated in the S5—S6 period. Among them, the SD8 family exhibited the highest ornamental value, with a color-changing period from the onset of discoloration (S2) to complete defoliation lasting 37 days.(2)The leaf color parameter a^* value of each family showed a linear upward trend, while the L^* and b^* values exhibited different change patterns. Specifically, greener leaves corresponded to lower a^* values, whereas redder leaves corresponded to higher a^* values, making a^* a representative parameter for the reddish leaf color of the five families.(3)Throughout the entire cycle, the chlorophyll and carotenoid contents of all T. cochinchinensis families decreased, while anthocyanin content increased, reaching a maximum at S3. The change from green to red leaves was mainly due to the proportionate distribution of pigment content. Before S3, chlorophyll content dominated the green leaf stage, and after S3, anthocyanin content dominated the red leaf stage.(4)During the color change from green to red, leaf thickness measurements indicated that pre-color change thickness was greater than post-color change thickness. The SD4 family experienced a significant 29.17% decrease in leaf thickness compared to other families (P<0.05). The upper epidermis thickness was greater than the lower epidermis across all families. Before the color change, the upper epidermis thickness of the SD6 family was significantly smaller than that of other families (P<0.05). Post-color change, the combined upper and lower epidermis thickness of the SD6 family accounted for the largest proportion among all families, significantly differing from others (P<0.05). Spongy tissue thickness exceeded palisade tissue thickness. The SD4 and SD6 families exhibited the most significant changes in spongy tissue thickness before and after the color change, at 30.59% and 0.87%, respectively. Palisade tissue thickness in the SD8 family significantly differed from other families (P<0.05), with a maximum change range of 29.92%.(5)Post-veraison, the leaf tissue structure of most T. cochinchinensis families showed that decreased leaf thickness, palisade tissue, and spongy tissue thickness facilitated anthocyanin accumulation, turning leaves red. No obvious variation attachments, such as particles or wax, were observed in leaf tissue, and no large air chambers appeared.【Conclusion】Leaf color change in T. cochinchinensis is primarily influenced by pigment dynamics, with anthocyanins being the main factor causing leaf reddening. Among the five families studied, the SD8 family demonstrated the most outstanding leaf color change and high ornamental value, making it particularly suitable for landscape greening. This study provides robust theoretical support for selecting T. cochinchinensis varieties and evaluating their ornamental value.