紫菜丝状体阶段核分裂特征观察

Observation on the characteristics of nuclear division of Porphyra (Rhodophyta,Bangiales) in conchocelis phase

对条斑紫菜和坛紫菜的果孢子、丝状体以及壳孢子的核分裂进行了细胞学观察。结果表明,两种紫菜染色体数分别是3和5,从果孢子萌发到壳孢子萌发阶段为二倍体核,核分裂都具同源染色体配对特征。在果孢子萌发和营养藻丝、孢子囊枝和壳孢子囊细胞分裂中,分裂前期末同源染色体紧密配对聚合,进入中期染色体在赤道面上排列,同源染色体仍一一对应,后期染色单体分离。在壳孢子萌发的核分裂中,前期同源染色体配对更加紧密,中期过程出现联会染色体分离的特征,后期同源染色体分离,显示减数分裂特点。本文还讨论了有丝分裂同源染色体配对现象对观察研究紫菜二倍体细胞核分裂的影响。

Cytological study on nuclear divisions of carpospores, conchocelis and conchospores was done on Porphyra yezoensis and Porphyra haitanensis. Haploid chromosome number was N= 3 in P. yezoensis and N= 5 in P. haitanensis. Diploid chromosome could be seen from carpospores germination to conchospores germination, while the nuclear division of conchocelis phase showed characteristics of homologous chromosome pairing. During the nuclear divisions of carpospores, conchocelis filament cells, conchosporangial branch cells and sporangial cells （conchospore formation）, homologous chromosomes paired up closely at late prophase, and at metaphase chromosomes moved to the equatorial plate, while homologous chromosomes were still parallel to one another, then sister chromosomes separated at anaphase as mitosis completed. In conchospores germination, homologous chromosomes paired up more closely in late prophase and the characteristic of synapsis chromosomes＇ separation appeared during metaphase; then homologous chromosomes detached at anaphase, showing meiosis characteristic. The influence of homologous chromosome pairing in mitosis on the observation and study of nuclear division in diploid cells of Porphyra was discussed.