Abstract:

Changnienia amoena Chien is a monotypic species and endemic to China, and was listed on the Chinese Red Book in 1992. The species was once abundant but has become rare and endangered in recent years because of the habitat fragmentation and unduly commercial collections. Previous observation showed that this species has very low and even no fruit set, and the pollinators are not observed before this report. The present observation was conducted at the Shennongjia, Hubei Province during the spring of 2002. The results showed that Bombus (Diversobombus) trifasciatus Smith¡, B. imitator Pittion and one species of Apis sp. visited the flowers of the orchid, but only B. trifasciatus could carry pollinaria on its body and was the legitimate pollinators of C. amoena. During 113 h of observation, only 9 visitations were recorded. The bumblebees mainly appeared during 12:00-15:00 during the day. Bumblebees stayed only a few seconds and never more than ten seconds in a flower. The flowers would persist in fresh about three weeks when they were not pollinated, but in three or four days after pollinated, the pollinated flowers underwent a series of color and morphological changes including stalk elongation and ovary swelling. Therefore, stalk elongation can be considered an index of fruits set. Artificial pollination indicated that C. amoena is a highly self-compatible and outcrossing species, but dependent on pollinators for fruit set. Based on these observations, we concluded that pollination system of C. amoena is deceptive. The fruit set in nature is not very low (26.98% on average) compared to other deceptive orchids, which may be related to small population sizes. The number of pollinia removal is much higher than that of fruit set, indicating that there are some degrees of pollinia wasting in C. amoena.

濒危植物独花兰的传粉生物学初步观察
孙海芹 罗毅波 葛 颂
（中国科学院植物研究所系统与进化植物学重点实验室，北京 1 0 0 0 9 3）

摘要： 独花兰（Changnienia amoena Chien）为我国特有的单种属植物，近年因生境破碎化和过度采挖，其野生资源日渐减少。迄今对独花兰极为有限的研究表明，其结实率很低或根本不结实，其传粉媒介也一直未被发现。2002年3~4 月，我们对神农架2 个移植居群和5 个天然居群进行了传粉生物学的定点观察，发现雌性三条熊蜂（Bombus(Diversobombus) trifasciatus Smith）、仿熊蜂（Bombus (Tricornibombus) imitator Pittion）和蜜蜂均访问独花兰，但只有三条熊蜂身体粘有花粉块，是独花兰的有效传粉者。三条熊蜂的访问频率很低，在113 h的观察中只有9次访问，但在一个天然居群 (population 3) 中曾观察到一天4次的最高访问频率；访问主要在12:00~15:00出现，但在花上停留时间很短，不超过10 s。在未被授粉的情况下，独花兰花朵大约3周后自然枯萎，但受粉后3、4 d内即出现一系列形态和颜色的变化，包括花梗逐渐伸长，子房在花梗逐渐停止伸长后开始膨大等，表明花梗伸长可作为结实（授粉成功）的指标。人工授粉实验表明，自花、异花受粉后花梗均伸长，而套袋隔离花的则花梗不伸长，说明独花兰是自交亲和的异交种，需要昆虫传粉。根据传粉者的访问频率、居群中果实的分布，尤其是花距内无花蜜等特征，我们认为独花兰是一种欺骗性传粉的兰花。相对于其他欺骗性传粉的兰花，独花兰的自然结实率并不很低（26.98%），这与居群规模小会提高欺骗性传粉兰花结实率这一观点吻合。花粉块的输出数远高于结实数，这说明独花兰存在一定的花粉浪费。
关键词： 独花兰；三条熊蜂；欺骗性传粉；长梗伸长

通讯作者。 E-mail: <gesong@ns.ibcas.ac.cn>。