摘要
应用透射电镜研究了圆叶牵牛（Ｐｈａｒｂｉｔｉｓｐｕｒｐｕｒｅａ （Ｌ．） Ｖｏｙｇｈｔ）和大花牵牛（Ｐ． ｌｉｍ ｂａｔａ Ｌｉｎｄｌ．）卵细胞在受精前和受精后质体和线粒体的变化。观察到卵细胞在受精前高度液泡化，在核周及卵细胞周围的薄层细胞质中有质体和线粒体。质体含１～２ 个较大淀粉粒。线粒体多呈环形或杯状。卵细胞受精后，细胞质增多，质体的数量也明显增加。质体基质变得更加浓厚，并且普遍含有嗜锇的球体。合子中线粒体丰富，但缺乏卵细胞中那种环形或杯状线粒体，多呈圆形。细胞质ＤＮＡ检测的结果表明，卵细胞质ＤＮＡ荧光有大小和形状不同的两类，它们在细胞中随机分布。一类较大，呈环状，可能是线粒体中的ＤＮＡ显示的荧光；另一类小的点状荧光，可能大多是质体ＤＮＡ荧光，前者比后者多。卵细胞受精后，细胞质类核发生变化，表现在数量上明显地比受精前少。研究揭示了牵牛花合子中细胞质ＤＮＡ 减少的现象，说明了母系质体ＤＮＡ 在受精后可能被降解，提供了母系质体不传递到后代的可能机制。
The ultrastructure and cytoplasmic DNA in the egg cell and zygote of Pharbitis purpurea,(L.) Voyght and P.limbata Lindl.which were studied with electron microscopy and DNA epifluorescence microscopy.The egg cell before fertilization was highly vacuolated with only a few cytoplasmic plastids and mitochondria.Plastids were spherical and/or rod shaped containing 1～2 large starch grains.Most of the mitochondria were cup and/or circular. The cytoplasm in the zygote was much more abundant than that in the egg cell.The number of plastids and their electronic density were greatly increased, in most of which containing osmiophilic bodies.The mitochondria were rich and spherical shaped in the zygote. Two types of cytoplasmic DNA nucleoids were detected in the egg cell,the more abundant one being big and circle shaped and the other dot shaped.Only dot shaped nucleoids were present in the zygote.The content of nucleoids in the zygote was much less than that in the egg cell.Authors propose that some cytoplasmic DNA may degenerate after fertilization. The ultrastructural characteristics of the egg cell and the reduction of cytoplasmic DNA in the zygote may related to the mechanisms of plastid unipaternal inheritance in Pharbitis.
基金
国家自然科学基金
