Using DGD embedment_free electron microscopy, ultrastructural observation on the intra_ and intercellular microtrabecular network (MN) of the pollen mother cells (PMC) of the whole meiotic prophase Ⅰ in onion ( Alli...Using DGD embedment_free electron microscopy, ultrastructural observation on the intra_ and intercellular microtrabecular network (MN) of the pollen mother cells (PMC) of the whole meiotic prophase Ⅰ in onion ( Allium cepa L.) was performed. Complex nuclear MN was observed in the nucleus of PMCs, spreading throughout the nuclear region. The nucleolus and chromosomes were connected with the MN filament network. The uniformity of nuclear MN changed with the development of the PMCs. A lamina_like structure surrounded the nucleus and joined the MN in nucleus and in cytoplasm, but it disassembled at the end of prophase Ⅰ. There was also a complex cytoplasmic MN in PMCs, without obvious variation during the prophase Ⅰ. Furthermore, MN in cytoplasmic connections (plasmodesmata and cytoplasmic channels) was noticed to link the frameworks in two neighboring PMCs into one entity. Cytomixis was observed at synizesis of prophase Ⅰ in this experiment, and MN in cytoplasm and in nucleus was noticed to distribute in these granules which migrated from one PMC into its neighboring cell. At this time the nucleus moved aside from center of the PMC, but the rest of the cell was still fulfilled with MN filaments. The relationships of nuclear MN with nucleolus and chromosomes, lamina with nucleus, as well as intra_ and intercellular MN with cytomixis are discussed in this paper.展开更多
The morphological structure, classification and meiotic behaviour as well as the possible origin of the extra centric fragment produced after intercellular chromatin migration (cytomixis) in pollen mother cells during...The morphological structure, classification and meiotic behaviour as well as the possible origin of the extra centric fragment produced after intercellular chromatin migration (cytomixis) in pollen mother cells during synizesis in rye have been studied by the squash and Giemsa·C-banding techniques. The results showed that the structures of extra centric fragments are metacentric, submetacentric, telocentric or subtelocentric, being quite different from each other. Their originations are stochastic, because any chromosome can be formed by the fragment. The meiotic behaviour of extra centric fragments is identical with that of B chromosomes. We consider that extra centric fragments are B chromosomes. The fragments originated from the fragmentation of A chromosomes at synizesis during cytomixis. Thus we consider that cytomixis could be one of the origins of B chromosomes.展开更多
文摘Using DGD embedment_free electron microscopy, ultrastructural observation on the intra_ and intercellular microtrabecular network (MN) of the pollen mother cells (PMC) of the whole meiotic prophase Ⅰ in onion ( Allium cepa L.) was performed. Complex nuclear MN was observed in the nucleus of PMCs, spreading throughout the nuclear region. The nucleolus and chromosomes were connected with the MN filament network. The uniformity of nuclear MN changed with the development of the PMCs. A lamina_like structure surrounded the nucleus and joined the MN in nucleus and in cytoplasm, but it disassembled at the end of prophase Ⅰ. There was also a complex cytoplasmic MN in PMCs, without obvious variation during the prophase Ⅰ. Furthermore, MN in cytoplasmic connections (plasmodesmata and cytoplasmic channels) was noticed to link the frameworks in two neighboring PMCs into one entity. Cytomixis was observed at synizesis of prophase Ⅰ in this experiment, and MN in cytoplasm and in nucleus was noticed to distribute in these granules which migrated from one PMC into its neighboring cell. At this time the nucleus moved aside from center of the PMC, but the rest of the cell was still fulfilled with MN filaments. The relationships of nuclear MN with nucleolus and chromosomes, lamina with nucleus, as well as intra_ and intercellular MN with cytomixis are discussed in this paper.
基金Project supported by the National Natural Science Foundation of China.
文摘The morphological structure, classification and meiotic behaviour as well as the possible origin of the extra centric fragment produced after intercellular chromatin migration (cytomixis) in pollen mother cells during synizesis in rye have been studied by the squash and Giemsa·C-banding techniques. The results showed that the structures of extra centric fragments are metacentric, submetacentric, telocentric or subtelocentric, being quite different from each other. Their originations are stochastic, because any chromosome can be formed by the fragment. The meiotic behaviour of extra centric fragments is identical with that of B chromosomes. We consider that extra centric fragments are B chromosomes. The fragments originated from the fragmentation of A chromosomes at synizesis during cytomixis. Thus we consider that cytomixis could be one of the origins of B chromosomes.
