雌雄异株植物鼠李生殖分配与生殖耗费补偿机制

Reproductive allocation and compensation mechanism for reproductive costs of dioecious shrub Rhamnus davurica

【目的】检验鼠李个体大小对其生殖分配的影响,比较相同径级雌雄鼠李生殖分配的差异,探讨鼠李可能存在的生殖耗费补偿机制,对今后雌雄异株植物生理生态学方面的研究提供论据支撑。【方法】在鼠李的花期和果期选择当年进行繁殖活动且生长状况与立地条件类似的植株作为调查样本,对每株鼠李的性别、叶生物量、花生物量(花期)、果生物量(果期雌株)进行了调查,通过Li-6400便携式光合作用测定仪比较不同性别鼠李叶片的光合能力。【结果】(1)大径级鼠李的生殖生物量与营养生物量均显著大于小径级鼠李(P <0.05)。(2)相同径级鼠李雌株的生殖生物量均显著高于雄株(P <0.05),雌雄鼠李的营养生物量没有显著差异(P> 0.05)。(3)当光强处于500~2 000μmol/(m2?s)时,鼠李雌株单位叶面积的光合速率大于雄株。【结论】研究区域内鼠李的个体大小对其生殖分配有显著影响,这是不同个体可利用资源总量不同造成的。鼠李雌株相较于雄株,并没有因较高的生殖耗费而缩减对营养生长的投入。鼠李雌株通过光合作用获得了更多的可利用资源来满足其生殖和营养生长过程需要,这种较强的光合能力是雌株在较高繁殖压力下进化出的一种生殖耗费补偿机制。

[Objective] The trade-offs between reproductive and vegetative processes have an important role in the life-history theory. Dioecious species afford an excellent opportunity to detect the trade-offs in resource allocation. [Method] This research selected the dioecious shrub Rhamnus davurica to examine trade-offs between reproduction and vegetative growth, and determine whether females reduce vegetative growth with the higher reproductive allocation. If female hadn’t showed less vegetative growth than male,whether compensation mechanism led to that or not. The investigated R.davurica was divided into 4 groups based on genders and DBH. The differences of reproductive allocation between genders were compared by ANOVA and multiple comparisons. We did photosynthetic experiment of R.davurica on early June 2012 using LI-6400 portable photosynthesis system. [Result] The main results were showed as: diameter level was positively correlated with reproductive biomass and foliage biomass(P < 0.05). In the same diameter level, the reproductive biomass(including flower and fruit biomass) was significantly different between genders(P < 0.05), but there was no significant difference between genders regarding the foliage biomass(P > 0.05). Photosynthetic capacity and the estimated light photosynthetic curves were different between the male and female. [Conclusion] We conclude that the relationship between vegetative growth and reproductive growth does not agree with trade-off theory, this is a result of difference in the total available resources, R.davurica in large diameter-class has more total available resources. Although in the same diameter level, females do not show less vegetative growth than males. It is due to their higher photosynthetic efficiency and carbon fixation capacity. This higher photosynthetic capacity is a compensatory mechanism for females whit higher reproductive pressure.