小麦离体花药中花粉核无丝分裂的电子显微镜观察

用电子显微镜观察到,在离体培养的小麦花药中,花粉细胞在脱分化分裂时,除了进行有丝分裂之外,还存在着两种类型的无丝分裂——劈裂(cleavage)和碎裂(fragmentation)。它们都是通过核膜的内陷实现的。认为劈裂式无丝分裂导致游离核花粉的形成,碎裂式无丝分裂导致微核花粉的形成,两者都可引起亚倍体和非整倍体植株的产生。

ELECTRON MICROSCOPICAL OBSERVATIONS ON WHEAT POLLEN NUCLEAR AMITOSIS IN VITRO

Electron microscopical observations revealed th at during the dediffe-rentiation division of wheat pollen nuc-leus,besides normal mitosis,amitosisi.e.cleavage and/or fragmentationcould also be happened in vitro.Whena nucleus underwent cleavage,thenuclear membrane invagination occur-red first,then the invagination extendedand reached to the opposite surface ofthe nucleus.So the nucleus was divided into two daughter nuclei with similarsize and often with a nucleolus respecti-vely.Following the nuclear membrane invagination,various organellescould enter the crack of the nucleus.The two daughter nuclei formed fromnuclear cleavage were very close eachother and between them there wasnot any "phragmoplast-plasmalemmacomplex" which separated the twodaughter nuclei formed from mitosis.The other type of pollen nuclear amito-sis was fragmentation,which took placeby nuclear membrane invagination too.But there were some differences in formof invagination between cleavage andfragmentation.When a fragmentationoccurred,the nuclear membrane in-vagination could take place at manypoints of nuclear surface at the sametime,then it extended and branchedin the nucleus.Finally the nucleuswas fractured into several micronucleiwith different contour and size.Thesedatum provided an explanation for theappearence of free nuclei,micro-nuclei and aneuploid in pollen embryo,callus and plant cell.It suggests that the cleavage amitosis mightcaused the appearence of the freenuclei,the fragmentation amitosis caused the micronuclei and both of themcould bring about the occurrene ofaneuploid.