西瓜小孢子发育过程中几种细胞器的变化

用透射电子显微镜观察了西瓜（Ｃｉｔｒｕｌｌｕｓ ｖｕｌｇａｒｉｓ Ｓｃｈｒａｄ．）小孢子发育过程中核糖体、线粒体、质体、内质网、高尔基体等细胞器的变化。核糖体和线粒体变化都有明显的规律性：核糖体密度在四分体时期高，液泡化时期降低，液泡化结束后再回升；线粒体经历一个脱分化与再分化周期，液泡化时期该细胞器数量及其内嵴数目减少而脱分化，液泡化结束后形状多样化、内嵴重新增多而再分化；质体结构不变，但体积变

ORGANELLAR CHANGES IN MICROSPORES OF CITRULLUS VULGARIS SCHRAD

Some organelles of watermelon microspores were observed by using transmission electron microscope.Ribosome density was high in tetrad microspores, very low in vacuoli zing ones,and high again after vacuolization came to an end.Mitochondria showed a cycle of dedifferentiation and redifferentiation.Disappearance of mitochondrial cristae and decrease of such organelle number during vacuolization stage were implications of the dedifferentiation,and reappearance of cristae and a variety of variations in shape after vacuolization indicated the redifferentiation.Plastids showed no structural modifications,but underwent evident changes in size.Most individuals reduced by several times when microspores were in va cuolization process,and then enlarged several times again after the process.Endoplasmic reticula changed from smooth type in tetrad microspores to rough type in vacuolized ones.Dictyosomes were copious before vacuolization,sparse after vacuolization stopped.It is evident that cytoplasm of watermelon microspores was reorganized.Cytoplasmic reorganization might be an inherent characteristic,for it conformed to spore development and was necessary for further development into 2 celled pollens.