Sakio Hitoshi, Nirei Takashi
Sado Island Center for Ecological Sustainability, Niigata University, Sado 952-2206, Japan.
Saitama Museum of Natural History, Nagatoro 369-1305, Japan.
Plants (Basel). 2022 Mar 11;11(6):753. doi: 10.3390/plants11060753.
Androdioecy is a rare reproductive system. , a woody canopy species in Japan's mountainous riparian zones, is described as a morphologically androdioecious species. In this study, we tried to detect whether is also functionally androdioecious. We analyzed its sexual expression, seed development, pollen morphology and germination ability, pollination systems, and mast flowering behavior. We found that the hermaphrodite trees are andromonoecious, with inflorescences bearing male and hermaphroditic flowers, whereas male individuals had only male flowers. Pollen morphology was identical in male flowers, in hermaphrodite flowers of an andromonoecious individual, and in male flowers of male individuals. Pollen from both types of individuals was capable of germination both ex vivo (on nutrient medium) and in vivo in pollination experiments. However, compared with pollen from andromonoecious trees, pollen from male trees showed a higher germination rate. The self-pollination rate of bagged hermaphroditic flowers was almost zero. The fruit set rate following cross-pollination with male pollen from a male tree was higher than that following natural pollination, whereas the rate with hermaphroditic pollen was the same. The flowering and fruiting of have fluctuated over 17 years; the flowering of the two types of sexual individuals exhibited clear synchronization during this period. The frequency of male individuals within the populations is 50%. The maintenance of such a proportion of males in populations of the self-incompatible is either indicative of a true androdioecious species with a diallelic self-incompatibility system or a cryptic-dioecious species. This alternative is discussed here.
雄花两性花同株是一种罕见的生殖系统。[物种名称]是日本山区河岸带的一种木本冠层物种，被描述为形态上雄花两性花同株的物种。在本研究中，我们试图检测[物种名称]是否在功能上也是雄花两性花同株。我们分析了其性表达、种子发育、花粉形态和萌发能力、授粉系统以及大年开花行为。我们发现，两性花树是雄花两性花同株的，其花序上既有雄花又有两性花，而雄株只有雄花。雄花、雄花两性花同株个体的两性花以及雄株的雄花中的花粉形态是相同的。在授粉实验中，两种类型个体的花粉在离体（在营养培养基上）和体内都能够萌发。然而，与雄花两性花同株树的花粉相比，雄树的花粉显示出更高的萌发率。套袋两性花的自花授粉率几乎为零。用雄树的雄花花粉进行异花授粉后的坐果率高于自然授粉后的坐果率，而用两性花花粉授粉后的坐果率相同。[物种名称]的开花和结果在17年中有所波动；在此期间，两种性别的个体的开花表现出明显的同步性。种群中雄株的频率为50%。在自交不亲和的[物种名称]种群中维持这样比例的雄株，要么表明这是一个具有双等位基因自交不亲和系统的真正雄花两性花同株物种，要么是一个隐性雌雄异株物种。本文对此进行了讨论。
