外来植物大花老鸭嘴在迁入地的传粉机制和繁殖策略

外来植物在迁入地的生存和繁殖策略,是入侵生物学研究的热门话题之一。开展入侵植物的繁殖策略研究,有助于深入了解入侵生物在迁入地的生存繁衍机制,对入侵植物在可控范围内的适当使用具有重要的指导意义。通过野外传粉昆虫观测、光学和电镜扫描观测和人工控制授粉等方法,对外来植物大花老鸦嘴（Thunbergia grandiflora）在广州和深圳的4个居群的开花物候、花部结构、花粉活力、传粉昆虫及其行为等传粉生物学特征进行了研究。结果表明：大花老鸦嘴的单花花期为1 d,上午10：00时花粉活力最高,长雄蕊花粉活力可达73.92%,短雄蕊花粉活力可达71.54%,随后花粉活力逐渐下降。主要传粉者为扁柄木蜂（Xylocopa latipes）,开花当天访花高峰期的9：00—10：00,单花访花频率可达5 h-1以上,之后开始逐渐减少,14：00之后未观测到扁柄木蜂访花,18：00后仅剩蚂蚁等体型较小的昆虫长期栖息于花序或花蕾。控制授粉实验结果显示,无论是人工异株授粉、自花授粉,还是自然授粉,结果率均为0,4个居群均未见结实。光学显微镜下子房发育完整;电镜扫描观测结果显示其花粉在柱头上能萌发,但花粉管不能延伸到子房位置。目前在园林栽培的大花老鸭嘴均以块根或茎为繁殖体培育苗木,虽然这些植株均能开出鲜艳的花朵,花粉传递者也充足,但未见任何结果现象。因此,初步推测本次研究区域内的大花老鸭嘴种群可能来自相同或相近的无性系,故不同居群间异株授粉的不结果现象可能为“自交不亲和”,或“染色体多倍化”所致。

Pollination and reproductive strategy of the alien plant Thunbergia grandiflora in the immigrated habitats

The survival and reproductive strategy of alien plants in new place have become the research hotspots recently. It is beneficial for exploring the survival and reproductive mechanisms of alien plants to investigate their breeding strategy, which will be useful for the reasonable exploitation of the alien plants. In this paper, the phenology, floral structure, pollen viability, pollinators and their behaviors of Thunbergia grandiflora were studied in four populations in Guangzhou and Shenzhen, Guangdong Province. The results showed that the florescence of single flower was one day only. The pollen viability of long stamen was the highest （73.92%） at 10： 00, and the short stamen is 71.54%, and it declined gradually after 12：00. The effective pollinator of T. grandiflora was Xylocopa latipes. The frequency of flower-visiting was higher （5 h-1） between 9：00-10：00 than any other flowering time, and the number of pollinator decreased after 13：00 pm. No any effective pollinators visit flowers of T. grandiflora after 14：00 except for a few ants inhabiting on the florescence. Field experiments indicated that the fruit set of all six treatments, among artificially out-crossed treatment, self-pollinated treatment, and natural pollinated treatment, was 0%. The growth of ovary was normal under the observation of light microscope （LM）. The result of scanning electronic microscope （SEM） showed that the pollens of T. grandiflora could germinate on the surface of stigma, but the pollen tubes were very short and could not grow into the ovary. The main artificial propagation way of T. grandiflora was the cloning with its tuberous roots and stems. Therefore, it was speculated that the plants of T. grandiflora coming from different populations in the study area might derive from the same or similar clones, and the genetic relationship of T. grandiflora are probably close between different populations. All out-crossed and self-pollinated flowers might be‘self-incompatiblility’ or‘chromosomal polyploid