桂南木莲繁育系统及其传粉适应性

Breeding Systems and Adaptation of Flowers in Manglietia chingi

为阐明桂南木莲(Manglietia chingi)自然条件下结实率低的原因及其传粉适应性意义,运用花粉活力测定、柱头可授性检测、传粉昆虫观察和套袋试验等方法研究其繁育系统及开花特征。结果表明:桂南木莲单花花期3~4 d,过程分为松蕊阶段、初次开放阶段、闭合阶段、再次开放阶段、衰败阶段;其中闭合阶段柱头可授性最强,花粉活力最高(31.34%),但雄蕊群未对外散粉;再次开放阶段雄蕊群对外散粉,但花粉活力低(8.85%);花朵两次晚上开放吸引少量甲虫访问,花朵白天下垂合拢滞留活力极低的花粉(1.93%)并吸引蜜蜂访问;桂南木莲的花粉/胚珠值(P/O)为12 430,属专性异交,自交不亲和。因此,桂南木莲二次开合、花朵下垂是对昆虫异交传粉机制的适应,自然条件下对外散出的花粉活力低、缺少有效传粉昆虫是其结实率低的主要原因。

In order to understand the reason of low seedsetting rate under natural condition in Manglietia chingi and its adaptation of pollination,we studied the breeding system and flowing characteristics by detecting pollen viability and stigma receptivity,observing pollinator,bagging text and other methods.The flowering of individual flower lasted for 3-4d,and it could be divided into five periods,stamens loosen stage,first opening stage,closing stage,second opening stage and withering stage.At closing stage,stigma showed the strongest receptivity,(31.34%),but stamens didn’t dispersed powder at that time.At second opening stage,the powder dispersed with low receptivity(8.85%).The twice opening of flower in night attracted a few beetles,drooping and closing flower in daytime could keep the pollen which the vitality is pretty low(1.93%)and attracted bees.The pollen/ovule ratio of M.chingi was 12430,which demonstrated that M.chingi was obligate crosspollination and no selfpollination breed system existed.In conclusion,flower drooping,twice opening and closing of M.chingi is an adaption to beetles pollination mechanism,and its fruit set is largely limited by the activity of pollen and pollinators under natural conditions.