Forest Environment Division, Forestry and Forest Products Research Institute, Ibaraki 305-8687, Japan.
Am J Bot. 2001 Mar;88(3):455-61.
I investigated the effects of display size and flowering phenology on fruit set in Aucuba japonica, an understory dioecious shrub pollinated by opportunistic insects. Natural variations in display size, flowering phenology, and fruit set were monitored in 1997. A hand-pollination experiment was also conducted to check whether pollen limitation was a factor in fruit set in the field. Increases in floral display size did not affect fruit set; the proportion of flowers that set fruit was almost constant irrespective of the total number of flowers per inflorescence, the total number of inflorescences per plant, and the total number of flowers per plant. The hand-pollination experiment showed that fruit set was not pollen limited despite the low mating probability that resulted from the combination of dioecism and the species' dependence on opportunistic pollinators. This was due, in part, to the fact that female flowers did not have a predetermined period of receptivity, but instead remained receptive until they received pollen. In contrast, flowering phenology did affect fruit set. Fruit set was most abundant when male and female flowering was most abundant. This suggests there was some degree of pollen limitation during the part of the flowering season when male flowers were scarce.
我研究了展示大小和开花物候对受机会主义昆虫传粉的林下雌雄异株灌木桃叶珊瑚座果的影响。1997 年，监测了展示大小、开花物候和座果的自然变化。还进行了人工授粉实验，以检查花粉限制是否是田间座果的一个因素。花展示大小的增加并没有影响座果率；有果实的花的比例几乎保持不变，而不管每花序的花总数、每株植物的花序总数和每株植物的花总数如何。人工授粉实验表明，尽管由于雌雄异株和物种对机会主义传粉者的依赖而导致交配概率低，但座果不受花粉限制。这部分是由于雌花没有预定的可接受期，而是在收到花粉之前一直保持可接受状态。相比之下，开花物候确实会影响座果率。当雌雄花最丰富时，座果率最高。这表明在雄性花稀少的开花季节的一部分，存在一定程度的花粉限制。
