作 者 ：Cai Xue and Hu Shi-yi
Keywords:Microtubule: Generative cell, Mitosis, Pollen tube, Lilium davidii,
Abstract:Previous observations indicated that division of the generative cell (GC) in some plant genura such as Lilium and Tradescantia is characterized by several unusual features, including persistence of surrounding microtubule (MT) bundles during mitosis, lacking a matephase plate, the cytokinesis is completed with furrow. The authors have further studied the changes of MT organizations and the chromosome (CHs) behavior in the GC during mitosis using electron microscopy and method of tubulin localizations. No MTs in the GC before GC division and during prophase was seen under electron microscopy. However, there was tubulin in the GC with antitubulin staining. During promatephase to matephase, the CHs appeared and arranged in a complexed tangled pattern lengthwise along the cell. Correspond- ingly, transverse pairs of kinetochores were located along the length and depth of the cell. They stacked successively like the rungs of a ladder. In this phase, a large mount of MTs appeared in the GC, which distributed in the cortex of the cell and among the CHs and along the whole length of the CHs. In the beginning, one or two kinetochore pairs changed from transversely to longitudinally situated in each cell. MTs ended on the kinetochore to form kinetochore MTs (KMTs). With the electron microscopy, authors did not find the image of lateral connection between the MTs and the kinetochores as previous reported with immunofluorescent method. As karyokinesis proceeded, more transverse kinetochore pairs gradually became longitudinal, and KMTs gradually increased in number. However, a distinct spindle was not evidenced. During anaphase, CHs seperation started at various positions along the length of the cell. The distribution of MTs in the GC was similar to that of promatephase to matephase. In late anaphase, the CHs segregated as two groups. Most MTs disappeared but only some remained in the polar regions and the interzone. Authors also measured and compared the lengths of the CHs and indirectly identified the existing anaphase B. During late tolephase, the MTs increased in number gradually in the region between the two newly formed sperm nuclei. The region might be the MT interdigitating zone visualized with antitubulin localization. The MTs disappeared after the cell plate (CP) appeared.
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