广西药食两用植物罗汉果自然种群有效传粉机制研究

Siraitia grosvenorii is a economically important plant due to the edible and medicinal value in Guangxi of China. However, severe pollination deficit had been found in the cultivated variety individuals of this plant, and consequently lead to a sharp rise of cultivation cost because of the highly depending on hand pollination. Given that wild populations of Siraitia grosvenorii can be naturally pollinated and regularly produce fruits, study on this pollination system might shed light on the predicament of pollination deficit in the cultivation. Taking wild population as study system, this project conducts the study on the natural pollination system from three aspects: effective pollination period, chemical signal, and the pollinator. Floral display, pollen vitality duration, and stigmatic receptivity duration will be investigated by consecutive observation and biochemical determination. The compositions and temporal change of both inflorescence volatile substance and nectar will be tested by periodical sampling and chromatographic analysis, and we will furthermore investigate the attracting function of both volatile and nectar compositions by using artificial flower of Siraitia grosvenorii as visiting object for flower visitors. Meanwhile, we will monitor the diurnal and nocturnal visitor groups of Siraitia grosvenorii by video camera, and record visiting behavior, including visitation rate and visit duration for each visitor group. Based on the result of monitoring investigation; a control visiting experiment will be conducted to identify the pollination effectiveness of each group in Siraitia grosvenorii florwe visitors. Finally, the aim of this project is to explore the important chemical signal and the key flower visitor in the effective pollination process of Siraitia grosvenorii natural populations, and to verify the potential fail-safe pollination mechanism which might composes of diurnal and nocturnal animal pollination in this species.

球果药食两用的罗汉果是广西重要的特色经济植物，在驯化栽培后遭遇严重的自然传粉缺失问题。鉴于罗汉果野生种群能正常传粉结实，对其自然传粉机制开展系统研究，可为深入认识和根本解决栽培罗汉果传粉缺失问题提供重要参考。拟对罗汉果自然种群传粉过程的时效性、化学信号和传粉者展开研究。采用连续观测和生化反应测定法，确定花部展示特征、花粉活力期和柱头可授期；并以分时段收集后进行色谱分析的方法，查明花序挥发性物质与花蜜的组分及其随时间变化式样，进一步以罗汉果仿真花为介质，检测不同组分对访花者的引诱功能；同时，通过录像监测，调查分析罗汉果白昼和夜间的访花类群及其行为特征，基于此设计控制性访花实验，检验不同访花类群的传粉效力。研究将最终揭示罗汉果有效传粉过程的重要化学信号和关键传粉者，并检验罗汉果是否具有白昼和夜间双传粉的“失效安全”机制，为有效阐明和根本解决栽培罗汉果的自然传粉缺失现象提供重要科学依据。

罗汉果的果实药食两用，广泛应用于食品、保健品和药品中。罗汉果在人工种植下自然授粉率很低，导致严重依赖人工授粉，成为制约罗汉果产业发展的核心问题之一。对罗汉果的开花特性、繁育系统和传粉过程进行了研究，主要结果如下：.1、花部综合征及其繁育系统。罗汉果花期7月-10月。雌雄花在凌晨4点开始慢慢开放，上午7点时花冠完全打开，下午4点花冠开始收缩闭合。花粉活力在7:00最强，随后逐渐减弱；柱头可授性在9:00最强，呈现先升高后降低的趋势。花粉/胚珠（P/O）比为1273.16±323.57，其杂交指数（OCI）为4，可知其繁育系统以异交为主，需要传粉者。.2、蜜腺及其花蜜分泌。雄花具有蜜腺且能分泌花蜜，其蜜腺体积较大，蜜孔数量多，其泌蜜节律呈双峰型，在9:00和14:00时出现泌蜜高峰期，花蜜的主要成分是蔗糖90.69%，葡萄糖4.42%，果糖3.49%；雌花虽具有蜜腺，但不能分泌花蜜。 .3、花、叶挥发性气味物质。雄花共鉴定出22种挥发性化学成分，主要成分是α-荜澄茄油萜；雌花共鉴定出17种挥发性化学成分，主要成分是辛烷；雄株叶子中共鉴定出17种挥发性化学成分，其主要成分是3-蒈烯；雌株叶子共鉴定出12种挥发性化学成分，其主要成分是乙醛。雌雄花分别特有12种和17中挥发性物质，雌雄株叶片分别特有5种和10种挥发性物质。 .4、访花昆虫种类及访花特征。雄花的主要访花昆虫有熊蜂、中华蜜蜂和无角栉距蜂，雌花的主要是无角栉距蜂。中华蜜蜂和无角栉距蜂访花时其背部会触碰到花药并携带花粉，可把花粉转运到雌花柱头，从而完成传粉过程。熊蜂是盗蜜者，不能携带花粉。无角栉距蜂对雌花的访问频率远低于雄花，这可能是罗汉果传粉受限的主要原因。.5、有效传粉昆虫的触角感器特征。无角栉距蜂是罗汉果的有效传粉昆虫，扫描电镜观察和分析显示：无角栉距蜂的触角为膝状，总共有板形感器等11种感器类型。板形感器是嗅觉器官，分布于无角栉距蜂触角F3~F11鞭节背面，认为其在准确定位罗汉果雌雄花协助其完成授粉中起着关键作用。