雌雄异株植物长梗柳传粉系统和生殖策略研究

Pollination System and Reproductive Allocation Strategies of Dioecious Tree Salix dunnii

摘要:

为探讨长梗柳(Salix dunnii)的传粉系统和不同性别的生殖投资策略，对居群性别比例、花部特征和访花昆虫进行了调查和观察，采用气相色谱-质谱联用技术(GC-MS)检测了花序的挥发性成分。结果表明，东边村居群的性别比例显著偏雄性(♂∶♀=1.28∶1, P < 0.05), 郭墩村和高地村的居群的性别比偏离不显著; 长梗柳雄株枝条的花序数显著多于雌株, 单花序的雄花数显著多于雌花, 雌花序平均长度显著大于雄花序; 长梗柳传粉系统是虫媒和风媒混合传粉系统, 主要访花昆虫为中华蜜蜂(Apis cerana)且显著偏好访问雌花; 吸引中华蜜蜂的挥发成分β-石竹烯的相对含量在雌花序中显著高于雄花序, 雌花序还具有β-榄香烯和芳香醇等吸引中华蜜蜂的特有挥发成分。因此, 长梗柳雄株在开花阶段投入了较多的资源产生雄花, 可能利于风媒传粉; 而雌株通过增加吸引传粉者的挥发成分来抵抗“传粉者限制”的效应, 可能利于虫媒传粉, 通过风媒和虫媒有效组合提升其繁殖效率。

Abstract:

To investigate the pollination system and reproductive investment strategies of Salix dunnii, the floral characteristics of flower and catkin and population sex ratio were investigated, the visiting insects were collected and their visiting frequency was calculated, the fruit and seed sets were calculated by bagging test, the volatile components of catkin were determined by gas chromatography-mass spectrometry (GC-MS). The results showed that the sex ratio of population in Dongbian Village was significantly male-biased (♂∶♀=1.28∶1, P < 0.05), while it was in equilibrium in populations of Guodun and Gaodi Village. The catkin number of male branches was significantly higher than that of female branches (P < 0.05), and the male flowers per catkins were significantly more than female flowers (P < 0.001), but the average length of female catkins was notably longer than that of male catkins (P < 0.001). Salix dunnii was wind- and insect-pollination, Apis cerana was the main visitor, which showed significant preference to visit female individuals (P < 0.001). The relative content of β-caryophylene in female, which is attractive to A. cerana, was significantly higher than the male (P < 0.001). Furthermore, β-elemene and linalool were only identified in female catkins, which were attractive to honey bee too. Therefore, it was suggested that male S. dunnii allocated more resource in producing male flowers at flowering stage, which was probably beneficial for wind-pollination, while female plants fought against the "pollinator limitation" by increasing the variety and output of volatile to improve insect-pollination. Salix dunnii possibly improve the reproductive efficiency via the combination of wind- and insect-pollination.