摘要
银杏为雌雄异株、风媒传粉植物。其雌花为裸露的胚珠,胚珠在传粉期不仅负责捕捉和识别空气中漂浮的花粉,而且形成花粉进入胚珠体内的通道和贮存花粉的结构,因此胚珠结构对银杏传粉效率和繁殖成效有重要影响。本文利用半薄切片和扫描电镜等技术观察传粉前后银杏胚珠形态与结构特征的变化,以揭示银杏适应风媒传粉的机制。结果表明:银杏胚珠发育过程中珠柄原基于当年12月首先发生,翌年1月珠被原基分化;3月中旬珠心组织和珠托分化形成,珠心组织分化的同时,周围珠被组织细胞不断分裂增殖,在珠心上方围合形成珠孔道,珠心内则分化形成孢原细胞;3月下旬胚珠珠孔开始开张,珠孔道伸长,珠心组织靠近珠孔端细胞发生解体死亡,贮粉室逐渐形成,孢原细胞逐渐伸长转变为大孢子母细胞;4月上旬,珠孔开张达到最大,并形成向外翻卷的漏斗状,珠孔处产生传粉滴,珠孔道的长度达到最长,贮粉室上方形成开口,大孢子母细胞减数分裂形成四分体,此时为传粉授粉最佳时期;传粉结束后传粉滴消失,珠孔、珠孔道及贮粉室闭合,雌配子体发育进入游离核阶段。以上结果显示经过长期的自然选择与生态演化,银杏胚珠已经具备了许多适应于风媒传粉过程中接受和识别花粉的结构特征。
Ginkgo biloba L.is a dioecious anemophilous species.Its female flower is a naked ovule which catches and identifies drifting pollens in the air during pollination and has specific structures to facilitate pollen entrance into the ovule and to store them.As a consequence,the ovule structures have important effects on pollination efficiency and reproductive success.To reveal the adaptive mechanisms of this species to anemophilous pollination,we investigated the morphological and anatomical characteristics of the ovule before and after pollination by using scanning electron microscopy and a semi-thin section technique.The results show that during the development of the ovule,the funiculus primordium first appeared in December and differentiation of the integument began in next January;finally,the nucellar tissue and ovule bracket forms in mid March.During the differentiation of nucellar tissues,integument tissues continuously proliferated to form a micropylar canal by surrounding and covering the nucellus and the archesporial cells gradually appeared inside the nucellus.From late March,the ovule micropyle began to open and the micropylar canal elongated.In addition,the pollen chamber was gradually formed by degeneration of nucellar tissues near the micropylar end and the archesporium slowly elongated and developed into megasporocytes.In early April,the micropyle opened outward like a funnel and reached its greatest width.Additionally,a pollination drop appeared on the micropyle and the micropylar canal reached its greatest length.Moreover,an opening was formed on top of the pollen chamber and a tetrad was formed after two divisions of the megasporocyte during meiosis.This was the period best for pollination.After pollination,the pollination drop disappeared,the micropyle,micropylar canal and the pollen chamber closed and then the female gametophyte reached the free-nucleus stage.The results indicate that the ovule of G.biloba forms complex morphological and structural adaptions to anemophily, presumably due to long-
出处
《北京林业大学学报》
CAS
CSCD
北大核心
2010年第2期79-85,共7页
Journal of Beijing Forestry University
基金
扬州大学高层次人才科研启动基金(2008)
国际科学基金(NoC/4560--1)
关键词
银杏
胚珠
风媒传粉
传粉生物学
Ginkgo biloba L.
ovule
anemophily
pollination biology
