以雌雄异株植物东北鼠李(Rhamnus schneideri var. manshurica)为研究对象, 分析不同繁殖阶段雌雄植株叶片元素含量的性别差异和动态变化, 可为雌雄异株植物性别特异性资源需求及利用策略提供理论参考。该研究在吉林蛟河天然针阔混交林内建立1块23.76 hm²的永久性固定监测样地, 于2019-2021年花期和果期(共5个繁殖阶段)选择样地内一定数量的东北鼠李雌雄植株, 测定每株的叶片营养元素(氮、磷、钾、钙、镁、铁、硼)含量, 比较东北鼠李雌雄植株在不同繁殖阶段叶片各营养元素含量的差异及动态变化; 并计算各个繁殖阶段雌雄植株的花、果生物量, 利用方差分析方法检验雌雄植株各个繁殖阶段的花果生物量差异, 以分析雌雄植株叶片营养元素出现性别差异及动态变化的背后机制。结果表明: (1)东北鼠李雌雄植株的叶片营养元素含量具有显著的性别差异, 但这种性别差异仅在某些繁殖阶段存在。在2019年花期, 雌雄植株的各叶片元素含量均无显著差异, 2021年花期, 雌株叶片的磷含量显著小于雄株。在2019年果期, 雌株叶片的磷、钾含量显著小于雄株; 而在2020年果期, 雌株叶片的氮、磷、钾、钙、镁、铁、硼含量均显著大于雄株; 在2021年果期, 雌株叶片的磷、钾、镁含量均显著大于雄株。(2)无论2019年还是2021年花期, 雄株的花生物量及花数均显著大于雌株。(3)果期雌株果数和果生物量大小排序为: 2020年> 2021年> 2019年。对不同繁殖阶段叶片营养元素含量进行分析, 发现东北鼠李雌雄植株的叶片各营养元素含量存在性别差异, 然而这种性别差异在不同繁殖阶段表现不同。在花期, 雌雄植株叶片元素含量性别差异不明显, 表明雄株并不会因为大量开花造成的高繁殖投入增加叶片元素含量储存; 而在果期, 雌株的叶片营养元素含量受其繁殖活动影响, 在结实较为丰厚的年份增加元素储存, 雌雄植株叶片营养元素含量的性别差异会更为显著。表明东北鼠李雌雄植株营养元素含量的性别二态性表现程度可能受植物个体所处繁殖阶段的影响和限制, 并且雌性个体繁殖资源投入越大, 这种性别二态性的表现就会越明显。

Aims To provide theoretical references for sex-specific resource requirement and utilization strategies of dioecious plants, we investigated the gender differences and dynamic changes of leaf element contents in male and female plants of Rhamnus schneideri var. manshurica at different stages of reproduction.
Methods Both male and female R. schneideri var. manshurica were selected from a permanent fixed monitoring sample plot of 23.76 hm² in a natural mixed coniferous and broadleaf forest in Jiaohe, Jilin. Foliar nutrient (nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), ferrum (Fe), and boron (B)) contents of each plant during five reproductive stages from 2019 to 2021 were determined and compared. The flower and fruit biomass of male and female plants were calculated for each reproduction stage. Differences in flower and fruit biomass between male and female plants at each stages of reproduction were tested using ANOVAs. Furthermore, we analyzed the mechanism underlying the occurrence and dynamics of gender differences in foliar nutrient elements of male and female plants.
Important findings (1) Gender differences in foliar nutrient contents of male and female R. schneideri var. manshurica were significant only at certain reproductive stages. During the 2019 flower period, there were no significant differences in foliar elemental contents between male and female plants. During the 2021 flower period, P content in female leaves was significantly lower than that of male plants. During the fruit period, foliar P and K content of female plants was significantly less than that of male plants. In contrast, foliar N, P, K, Ca, Mg, Fe and B contents of female plants were significantly greater than male plants in the 2020 fruit period. During the 2021 fruit period, foliar P, K, and Mg contents in female plants was significantly greater than male plants. (2) Flower biomass and flower number of male plants were significantly greater than female plants during flower periods in both 2019 and 2021. (3) At the fruiting stage, the order of fruit number and fruit biomass of female plants was 2020 fruit period > 2021 fruit period > 2019 fruit period. There were gender differences in foliar nutrient contents, which were expressed differently at different stages of reproduction. During the flower period, there was no significant difference in leaf element content between male and female plants, indicating that male plants do not increase leaf element content stores due to high reproductive inputs during heavy flowering. However, during the fruit period, foliar nutrient contents in female plants was influenced by reproductive activities, and the increase in nutrient stocks in more fruit-bearing years contributed to the more pronounced sex difference in nutrient contents. Our results suggest that the degree of sexually dimorphic expression of nutrient content in male and female R. schneideri var. manshurica may be influenced and limited by the reproductive stages, and that the greater reproductive resource inputs of female, the more pronounced sexually dimorphic expression.