云锦杜鹃的开花动态与繁育系统研究

对3个云锦杜鹃种群的开花动态和传粉方式等野外定位观测结果显示:花芽在花朵开放后形成雏 形,经过8～9月的生长后成形,次年4月复苏,形成含6～12朵花的总状伞形花序,5月初开花,花期接近25 d。花生命周期为5～8d,其中种群G的周期最短,平均为5.8d,主要原因是光照时间长,湿度相对较低,花形 态较小。开花后第二天到第三天,花药开裂,散出粘连成串的花粉,悬挂在花柱的中上部,同时柱头进入可授 期;第五天到第六天,花瓣与花托分开并前移到花柱,使花柱倒垂,花粉串能粘附到柱头上。根据人工授粉试 验和花粉落置观察的结果,云锦杜鹃的繁育系统为混合交配型,自然条件下为花后自花授粉,主要借助花瓣脱 落来传播花粉;但根据杂交指数估算和花粉-胚珠比测定,云锦杜鹃的繁育系统为异交,自交亲和,需要传粉 者,说明云锦杜鹃可能是由虫媒传粉向自花传粉演化。

Studies on floral dynamic and breeding system of Rhododendron fortunei

The floral dynamics and breeding characteristics of Rhododendron fortuneiwere studied. The flower buds,formed after flowering,get their shape after a fast development from August to September,and keep their shape through the winter. The winter buds resurrect in April of the next year and grow into cyme-botrys,containing 6 to 12 flowers. R.fortunei flowers in May and lasts for about 25 days. Every flower has a life span of 5～8 days. Affected by a long sunshine and low air humidity in population G, under a Pinus taiwanensis forest,the flowers are smaller and the life-span of a flower is shorter than that of the other two populations. The flowering procedure of R.fortunei is anther dehiscence,which emits pollen cluster hanging on the upper part of the style from the second day to the third day. Simultaneously,the stigma colour changes from light green to orange,showing the stigma coming of reception. Then,petals shed off and move to style from fifth day to sixth day,which reverse the style and make the pollen clusters touch the stigma. Based on the results from some artificial treatments and the pollen loading,we get the result that the breeding system of R.fortunei is maxing mating, and self-pollination through petal’s shedding off is its main natural pollination method. But according to Dafni’s outcrossing index and the pollen-ovule ratio,the breeding system of R.fortunei is pollinator,outcrossing and self-compatible. So we conclude that R.fortunei is probably on a transition stage from outcrossing to selfing.