珍稀濒危沉水植物水菜花传粉生物学研究

Pollination biology of the rare and endangered submerged plant, Ottelia cordata

关键词:  雌雄异株, 欺骗性传粉, 繁育系统, 花粉限制, 水鳖科

Key words:  dioecism, deceptive pollination, breeding system, pollen limitation, Hydrocharitaceae

摘要:

水菜花(Ottelia cordata)是珍稀濒危的沉水植物,现仅分布在中国海南岛北部海口至文昌一带的淡水湿地,其造型优美,极具园艺观赏价值。然而,受人类活动影响,水菜花的生境急剧退缩且更加破碎化,濒临灭绝。为探究水菜花的繁殖特征和繁殖规律,该研究分析了水菜花的花部形态、性比、花粉活性、柱头可授性、反射光谱、花粉限制与无融合生殖及其传粉者类型与行为。结果表明:(1)水菜花雌雄异株,雌、雄个体的性比约为1:2; 水菜花雌、雄花形态相似,但雌花略大于雄花。(2)水菜花花粉活性和柱头可授性在花蕾期和开放期均较高。(3)中华蜜蜂(Apis cerana)是水菜花的主要传粉者,传粉效率较高且访问雄花的频率显著高于雌花。(4)水菜花雄蕊、雌蕊间的花色距离显著高于中华蜜蜂辨别的阈值(P<0.001)。(5)在自然授粉和人工授粉下,水菜花坐果率分别为95.29%和98.42%,并且不存在无融合生殖现象。综上所述,水菜花两性模拟的欺骗性传粉并不完美,传粉者可以从视觉上区分雌花和雄花; 而由于水菜花雄花数量较多,传粉者低频率的“错访”足以达到水菜花雌花的繁殖需求。因此,在今后开展水菜花迁地保护、人工种群恢复等保育工作时,应重视水菜花种群大小、性别比例和当地传粉者种群数量。

Abstract:

Ottelia cordata is a kind of rare and endangered submerged plant that grows in freshwater wetlands in northern Hainan Island, from Haikou to Wenchang in China. This species is known for its beautiful appearance and the distinct “flower river” landscape, which makes it a high ornamental value. With the intensification of human activities, the habitat of O. cordata has been sharply reduced and fragmented, leading to its endangerment. In order to explore the reproductive characteristics and reproductive laws of O. cordata, the flower morphology, sex ratio, pollen viability, stigma receptivity, reflectance spectrum, pollen limitation and apomixis, and the types and behaviors of pollinators in O. cordata were analyzed. That is, the pollination biology of O. cordata were studied for its further in-situ and ex-situ conservation. The results were as follows:(1)The flowers were dioecism, and the sex ratio of female and male individuals was about 1:2; the morphologies of male and female flowers were similar, and the female flowers were slightly larger than the male.(2) O. cordata had high pollen viability and stigma receptivity in budding and blooming phases.(3)Apis cerana was the main pollinator of Ottelia cordata, which visited male flowers more frequently than female flowers, with higher pollination efficiency.(4)The distance between the color loci of pistils and stamens was significantly higher than the discrimination threshold of Apis cerana.(5)The fruit setting percentage under natural pollination was similar to that under artificial pollination(95.29% and 98.42%, respectively), and there was no apomixis and low pollen limitation in the natural population of Ottelia cordata. In conclusion, the deceptive pollination of O. cordata simulated by both sexes is imperfect. Pollinators can visually distinguish female and male flowers. However, the large number of male flowers of O. cordata attracted many insects to visit flowers, which increases the probability of “mistake” pollination and is enough for the reproductive needs of female flowers. Therefore, future ex-situ conservation and artificial population restoration should pay more attention to population size, sex ratio and the number of local pollinators.