草豆蔻传粉生物学的研究

Pollination biology of Alpinia hainanensis (Zingiberaceae)

比较研究了花柱卷曲性植物草豆蔻 Alpinia hainanensis两种表型(上举型和下垂型)的传粉生物学特性。结果表明:草豆蔻的花柱卷曲运动节律与其他已报道的山姜属Alpinia植物基本一致,而下垂型花的花柱卷曲运动明显滞后于上举型花约2 h。草豆蔻的花柱卷曲运动中存在一些不同步的现象,甚至在同一花序上的两朵花的花柱运动节律亦会表现出不一致的现象,但上举型花的花药开裂时间却严格同步,都发生在同类型个体的柱头全部位于花药上方之后进行。草豆蔻上举型花的花蜜分泌量、单花花粉量、花粉/胚珠比率(P/O)均明显比下垂型花多,而两种表型的胚珠数、花蜜糖含量、氨基酸含量无显著差异。在草豆蔻的单花期内不同时间段进行人工授粉,上举型花在其柱头位于花药下方时进行人工授粉,其结实率明显比柱头位于花药上方时人工授粉的处理高,下垂型花则没有显著差异。在自然居群中,草豆蔻的主要传粉者是无垫蜂Ameglla sp.和两种木蜂Xylocopa sp.,但存在传粉者不足而影响结实率的现象。完全套袋、去雄和去雌(去柱头)处理的均不结实,表明草豆蔻中不存在无融合生殖、主动自花授粉和滞后自交的生殖保障现象。而人工自交和异交均具有较高的结实率,表明草豆蔻为自交亲和植物。草豆蔻的繁育系统是具花柱卷曲性运动的异花授粉的交配?

Comparative studies on pollination biology of two floral morphs in Alpinia hainanensis were carried out in Hainan Province and Guangzhou, Guangdong Province, southern China. Populations of A. hainanensis have two floral morphs and the behaviors of stylar movements in the two floral morphs are similar to those found in other species of Alpinia previously reported. However, the stylar movement behavior of the cataflexistylous morph is 2 h slower than that of the anaflexistylous morph. There are some asynchronous stylar movements on the same floral morph, even on the same inflorescence. Yet, all anthers of the anaflexistylous floral morphs dehisce only after all stigmas of the same phenotype have moved out of the receptive position, viz., above the anthers. Our results indicate that the anaflexistylous morph has more pollen grains per flower, higher pollen/ovule ratio (P/O), and larger nectar volume than the cataflexistylous morph, while approximately equal ovule numbers, sugar and amino acid concentration. Field experiments indicate that the fruit sets are significantly high in both artificially out-crossed and self-pollinated flowers, while no fruit set was observed in bagged emasculated flowers and the unpollinated bagged flowers. These facts exhibit that A. hainanensis is self-compatible and there is no self-pollination and agamospermy in the species. There are significant differences in the fruit sets among the anaflexistylous flowers with hand-pollination treatments at different times during the day, but not in the cataflexistylous flowers. The fruit set by hand pollination is much higher than that under natural condition. This means that A. hainanensis is dependent upon insects for pollination, and insufficiency of pollinators limited fruit set under natural condition. The effective pollinators were Ameglla sp. and two species of carpenter bees (Xylocopa sp.). However, only fewer insects at a lower frequency visited flowers of A. hainanensis in nature. The breeding system of A. hainanensis is xenogamy with flexistyly.