扇脉杓兰花粉超微结构及花粉管生长的观察

为明确扇脉杓兰花粉形态结构及雄性生殖特性,利用扫描电镜、透射电镜和荧光显微镜对花粉形态和超微结构及花粉管生长过程进行观察。结果表明:(1)扇脉杓兰单粒花粉长球形,表面光滑无特征纹饰,有少量胶黏物质,一些表面有2个或以上的深凹陷,凹陷内有球形突起的内容物。(2)花粉壁分为由棒状的基柱小单元组成的外壁和纤维素果胶组成的内壁,有覆盖层;生殖细胞近圆形,细胞核大而致密;营养细胞多弧形,核质分散;花粉粒细胞质含有大量的线粒体、质体和小泡等细胞器,淀粉、蛋白质和多糖含量丰富。(3)花粉管萌发后沿子房壁方向伸长,授粉20d花粉管伸长生长并不明显,授粉30d伸长的花粉管中出现大量胼胝质塞,并且伸长方向转为胚珠中间,花粉管逐渐接近胚珠,在授粉后50d基本完成受精作用。研究认为,扇脉杓兰花粉发育正常,不阻碍有性生殖过程。

Ultrastructure of Pollen and Observation on Pollen Tube Growth in Cypripedium japonicum

In order to have a knowledge of pollen morphology and structure as well as male reproductive characters of Cypripedium japonicum Thunb.,we used SEM(scanning electron microscopy) and TEM (transmission electron microscopy) and fluorescence microscopy to observe pollen ultrastructure and the process of pollen tube growth.The results showed that:(1)Pollen grain presented prolate,smooth surface with a small amount of glue materials and without any characteristics,while some of the surface had two or more deeper depression with spherical protrusions inside.(2)Pollen wall divided into the inner wall with cellulose pectin composition and the outer wall of rod-shaped pillar structure,with covering layer outside.Germ cells were nearly round,of large and dense nucleus;vegetative cells were more curved,with nuclei and cytoplasm dispersion.Pollen cells contained a large number of mitochondria,plastids,vesicles and other organelles,and were rich in starch,protein and polysaccharide.(3)Pollen tubes grew along the direction of elongation of the ovary wall after germination.Twenty days after pollination (DAP),few pollen tubes grew on the ovary wall.A huge number of callose plugs presented in pollen tubes which changed the elongation direction to the middle of ovule 30 DAP.Along with pollen tubes approaching to the ovules,fertilization basically completed 50 DAP.Our study suggested that pollen could develop normally in C.japonicum,which did not hinder the process of generative propagation.