黑面神雌花气味传粉前后的变化及其生态意义

Variation of floral scent emitted by the female flowers of Breynia fruticosa(Phyllanthaceae)at pre-pollination, pollination and post-pollination stages and its ecological significance

关键词:  花气味, 气相色谱-质谱联用法, 传粉前后, 黑面神, 头细蛾, 专性传粉互利共生关系

Key words:  floral scent, GC-MS, pre- and post-pollination stage, Breynia fruticosa, Epicephala moth, obligate pollination mutualisms

摘要:

该文以与头细蛾传粉相关的叶下珠科植物黑面神为材料,采用动态顶空吸附法分别收集了该物种雌花传粉前后释放的挥发物,利用气相色谱-质谱联用技术分析了其化学成分,探索了三者间花气味的异同,并对其生态意义进行了讨论。结果表明:从该物种传粉前、传粉期和传粉后的雌花气味中共分离出22种挥发物(传粉前12种,传粉期15种和传粉后13种),以脂肪族衍生物和萜类物质为主。3-己烯醛、反-2-己烯醛、顺-3-己烯-1-醇、顺-乙酸-3-己烯酯、反-β-罗勒烯、β-石竹烯、β-蛇麻烯、反,反-α-金合欢烯和长叶烯是其主要挥发物。传粉前后雌花气味的化学种类及组成发生了显著分化,且这种变化主要是由于各时期主要挥发物发生改变而引起的。反-β-罗勒烯在传粉期含量最高,而在传粉后显著下降,3-己烯、反-2-己烯醛、顺-3-己烯-1-醇和顺-乙酸-3-己烯酯在传粉前含量均最高,β-石竹烯含量在传粉后显著升高,且长叶烯仅在传粉后出现。在传粉期和传粉后β-蛇麻烯和反,反-α-金合欢烯的含量均显著上升。同时,传粉期雌花的释放量明显高于传粉前和传粉后的。综上结果显示,黑面神雌花传粉前后花气味发生了质与量的改变。初步推测黑面神雌花传粉前后花气味的分化可能会有效阻止头细蛾对其进行再次访问,限制头细蛾在其雌花中过度产卵,进而来减少传粉头细蛾对宿主种子的取食,这无疑对维持叶下珠科植物-头细蛾专性传粉互利共生体系的稳定性具有重要的化学生态意义。

Abstract:

The floral scent is the key chemical signals for maintaining nursery pollination mutualisms between Phyllantheae plants and Epicephala moths. At pollination stage, the floral scent could guide obligate pollinators to encounter their host plants for pollination service and laying eggs. Until post-pollination, it also plays other potential ecological functions. Here, floral volatiles of female flowers of Breynia fruticosa(Phyllanthaceae)at pre-pollination, pollination and post-pollination stages were collected by dynamic headspace absorption technique, respectively, then chemical components using gas chromatography-mass spectrometry(GC-MS). We have determined whether there are variations of floral scent at pre-pollination, pollination and post-pollination stages by conducting principal component analysis. The results showed that a total of 22 volatile compounds were detected from the floral scent of female flowers of B. fruticosa at pre-pollination stage(12 compounds), pollination stage(15 compounds), and post-pollination stage(13 compounds), which were mainly contained fatty acid derivatives and terpenoids. 3-Hexenal,(E)-2-Hexenal,(Z)-3-Hexen-1-ol,(Z)-3-Hexenyl acetate,(E)-β-Ocimene, β-Caryophyllene, β-Humulene,(E,E)-α-Farnesene and Longiborneol were considered as the major scent component(the relative amount>5% ). Multivariate statistical analysis showed there were obviously qualitative differences in chemical compositions of the floral scents from female flowers at pre-pollination, pollination and post-pollination stages, and such differences were result from changes of the main scents compounds among different flowering stages. For example, the content of(E)-β-Ocimene is the highest at pollination stage, whereas it significantly decreased after pollination. 3-Hexenal,(E)-2-Hexenal,(Z)-3-Hexen-1-ol and(Z)-3-Hexenyl acetate are the four most abundant compounds at pre-pollination stage. β-Caryophyllene obviously increased and Longiborneol newly appeared at post-pollination stage. Both β-Humulene and(E,E)-α-Farnesene sigificantly increased at pollination and post-pollination stages. In addition, the volatile release amount of female flowers at pollination stage emitted significantly more volatiles than that at pre- and post-pollination stages, respectively. The strong reduced emission of floral bouquet and significant variation in the chemical composition in female flower scents at post-pollination stage may be a function as post-pollination mechanisms to efficiently reduce further flowers visit, thereby to limit seed predation. It was specultated that such qualitative and quantity differentiation in floral scent from Phyllantheae plants at pre-pollination, pollination and post-pollination stages might have the important chemical ecological significance for maintaining in stability of nursery pollination mutualisms between Phyllantheae species and Epicephala moths.