半扭卷马先蒿个体内的种子生产模式及其对资源的响应

花序内部雌性繁殖成功的差异在很多植物当中都存在,解释花序内部雌性繁殖成功的假说主要有3种:传粉不均匀假说、结构效应假说和资源限制假说。但外部因素对植物花序内雌性生殖成功模式的影响的研究非常少。本实验对半扭卷马先蒿设置了3个密度梯度、2个剪叶水平,收取不同部位的果实,以研究密度和剪叶对半扭卷马先蒿个体内种子产量的影响。实验参数包括:单个果实种子数、种子重、种子均重和胚珠数。同时,还做了人工补充授粉和自然授粉单个果实种子数/胚珠数和单株果实数/花数的比较实验,结果证明,半扭卷马先蒿的繁殖不受花粉资源的限制;密度对单个果实的种子数、种子均重有显著影响。剪叶对单个果实的种子数、败育数、胚珠数、种子重有显著影响。剪叶和位置的交互作用在单个果实的种子数、败育数、胚珠数方面有显著作用,密度和位置的交互作用对上述参数均无显著影响。在剪叶和密度处理下,位置对果实的上述参数均有显著影响,剪叶植株的单个果实种子数、败育数、胚珠数、种子重均小于未剪叶的植株。由此可以看出,在半扭卷马先蒿的雌性繁殖成功当中,结构效应和资源限制假说可能同时起着作用。且资源条件不但影响着半扭卷马先蒿雌性生殖成功,而且影响着花序内的变异程度,表明了该种植物对种子生产的可塑性调节。

The pattern of seed reproduction and its response to resources in Pedicularis semitorta individuals

There is a common phenomenon that a discrepancy in female productive success exists in the inflorescence of many plants, especially alpine plants. The non-uniform pollination hypothesis, the architecture effect hypothesis, and the resource competition hypothesis are three hypotheses to explain such patterns of within-inflorescence variation in female reproductive success. However, experiments to evaluate the influence of outside environmental factors on female reproductive success are rare. In this experiment, the effects of population density and defoliation on the female productive success of P. semitorta were investigated. The parameters tested include seed number, seed mass, ovule number per fruit, and individual seed weight. We also choose twenty natural groups of P. semitorta to find whether this plant’s reproduction allocation is restricted by pollen resources. There was no significant discrepancy in the rate of fruit set and the rate of seed set between natural pollinated and artificial supplement pollinated plants. However, population density had a significant effect on seed number per fruit and individual seed weight, while defoliation affected seed numbers, seed mass, and ovule number per fruit. In density and defoliation treatments, fruit position had a marked relationship to all the above parameters, indicating that architecture effects play a role in this plant’s female reproductive success. All the parameters of defoliated individual plants were less than those of the non-defoliated ones. The interaction effect of defoliation and fruit position had a significant influence on seed numbers and ovules per fruit, indicating that defoliation had a negative effect on female reproductive success. We suggest that the architecture effect and resource competition both affect female reproductive success of P. semitorta and that they are the results of plant plasticity.