植物复叶形态和光合功能是对生境响应的最直观表现之一, 复叶光合能力和小叶数量直接反映出植物对生境的适应性。水曲柳(Fraxinus mandschurica)雌雄株存在一定的形态差异, 其复叶在不同生境下也可能存在不同的适应性, 为进一步分析雌雄异株型个体叶片对生境异质性的差异响应, 该研究以长期生长在干旱盐碱生境和适宜生境的水曲柳成熟雌株和雄株复叶为研究对象, 分析了两种生境中雌株和雄株复叶之间的性别差异以及不同小叶数量复叶间形态和光合功能性状的差异。研究发现: (1)和适宜生境相比, 干旱盐碱生境中水曲柳雌株和雄株同一小叶数量复叶的形态和光合能力虽未表现出性别差异, 但雌株9小叶型复叶数量占比的增加量高于雄株29.13%, 11小叶型复叶数量占比的下降量高于雄株33.74%, 雌株9小叶型复叶的光合速率下降量高于雄株10.98%。(2)在适宜生境中, 雄株复叶数量集中分布在9小叶型和11小叶型, 雌株复叶数量集中在11小叶型, 雌株和雄株11小叶型复叶的比叶面积大于7小叶型和9小叶型复叶, 干物质含量显著高于7小叶型和9小叶型复叶; 在干旱盐碱生境中, 雌株和雄株的复叶数量集中在9小叶型, 虽然雌雄株9小叶型复叶的比叶面积小于11小叶型复叶, 但9小叶型复叶的叶干质量高于11小叶型复叶; 两生境中雌株和雄株9小叶型和11小叶型复叶的净光合速率也无显著差异。(3)在复叶形态和气体交换能力指标中, 复叶的小叶数量占比、叶干质量、比叶面积和净光合速率具有较高的可塑性。综上所述, 在适宜生境下, 水曲柳雌雄株复叶的形态存在性别差异, 表现为雌株主要发育11小叶型复叶, 雄株主要发育9小叶型和11小叶型复叶, 雌雄株间的光合功能未表现出性别差异; 而在干旱盐碱生境下, 水曲柳雌雄株复叶的形态和光合功能未表现出性别差异, 雌株和雄株均主要发育9小叶型复叶。该研究为雌株和雄株复叶在不同生境下生长发育的性别差异提供了理论依据, 也为雌雄异株型乔木雌株和雄株复叶的生态适应性提供了数据支撑。

Aims The morphology and photosynthetic functions of compound leaf are one of the most intuitive manifestations of plant response to habitats. The changes of photosynthetic capacity and number of leaflets of compound leaf directly reflect the adaptability of plants to habitats. There are some morphological differences between male and female Fraxinus mandschurica, and their compound leaf may have different adaptabilities in various habitats.
Methods This experiment took compound leaves male and female mature F. mandschurica growing in the drought saline-alkali habitat and suitable habitat as the research materials. The gender differences between female and male plants and the differences of morphology and photosynthetic function between compound leaf with different numbers of leaflets under two habitats were compared and analyzed.
Important findings The results showed that (1) compared with the suitable habitat, the morphology and photosynthetic capacity of compound leaf with the same number leaflets of female and male F. mandschurica under the drought saline-alkali habitat did not show gender difference, but the increment of percentages of compound leaf with 9 leaflets of female plants was 29.13% higher than that of the male plants, the decrement of percentages of compound leaf with 11 leaflets was 33.74% higher than that of the male plants, and the decreament of photosynthetic rate of compound leaf with 9 leaflets of female plants was 10.98% higher than that of the male plants. (2) Under the suitable habitat, the proportion of compound leaves of male plants was mainly concentrated within 9 and 11 leaflets, while the proportion of compound leaf of female plants was mainly concentrated within 11 leaflets. Meanwhile, the specific leaf area and leaf dry mass of compound leaves with 11 leaflets of female and male plants were greater than that of compound leaf with 7 and 9 leaflets. Under the drought saline-alkali habitat, the proportion of compound leaf of female and male plants was mainly concentrated in 9 leaflets. The specific leaf area of compound leaf with 9 leaflets of male and female plants was less than that of 11 leaflet compound leaf, whereas the leaf dry mass showed the opposite trend. There was also no significant difference in the net photosynthetic rate of compound leaf with 9 and 11 leaflets between female and male plants in the two habitats. (3) Among the indexes of compound leaf morphology and stomatal gas exchange capacity, the percentages of compound leaf with different number of leaflets, leaf dry mass, specific leaf area and net photosynthetic rate of compound leaf have high plasticity. Therefore, under the suitable habitat, there is no gender difference in the photosynthetic function between male and female plants, but there are gender differences in the morphology of compound leaf of male and female F. mandschurica, which are shown as follows: the female plants mainly developed the compound leaf with 11 leaflets, and the male plants predominantly developed the compound leaf with 9 leaflets and 11 leaflets. However, under the drought saline-alkali habitat, the morphology and photosynthetic function of compound leaf of male and female F. mandschurica did not show gender differences, and both female and male plants mainly developed the compound leaf with 9 leaflets. This study provides a theoretical basis for the gender difference in the growth and development of compound leaf in different habitats, and also provides data support for the ecological adaptability of compound leaf of dioecious trees.