Since nuclear extrusion was rediscovered in young Allium scale by S.H.WU in the years of 1950's systematic investigations on this phenomenon were carried out with various kinds of microscopic techniques and plant materials to collect more effective evidence to clarify the debate about whether the nuclear extrusion is an artifact or normal event. In the cooperative research of S. H. WU and C. H. LOU the normality of the occurrence of nuclear extrusion either in growing part of plant or in senescent tissue has been confirmed. This event is intimately associated with the physiological state of the tissues/cells and may play an important role in redistribution and reutilization of cell contents. Based on the results obtained a hypothesis of intercellular movement of protoplasm as a means of translocation of organic material in plants was suggested. Chromatin extrusion was also discovered in the pollen mother cells (cytomixis) of certain angiosperms by G. C. ZHENG and his team. Intercellular migration of chromatin appears most frequently at the stage of synizesis. Cytomixis has been studied in relation to variation and evolution. Chromosome aberration has been considered to be closely associated with chromatin extrusion. By vital microscopic observations of the live tissues of garlic (Allium sativum L.) bud and wheat (Triticum aestivum L.) ovule combined with cinemicroscopy and video recording it has been uncovered that, not only the nuclear material but also the cytoplasm could traverse the intercellular channels by vigorous contraction and expansion, and they may simultaneously extrude out of a cell but often asynchronously migrate from one cell to another. The involvement of cytoplasmic constituents in intercellular migration was also detected in pollen mother cells with electron microscopy. Regarding the mechanism of intercellular movement a series of experiments provide convincing evidence showing that this kind of movement is an active metabolic process closely coupled with energy metabolism, and t
Actin and myosin were found to be associated with the cytoplasmic sleeve of plasmodesmata. As cytoskeletal proteins, actin and myosin are believed to regulate the conductivity of plasmodesmata （PDs） in higher plants. Using immunocytochemical methods, we found the two proteins to be co-localized - and closely linked to each other - in plasmodesmata and ectodesmata-like structure in ageing parenchymatous cells of Allium sativum L. We suggest that intercellular communication is affected by the interaction between actin and myosin.
DONG Yu LIU Na LIU Gang LI Wen-long YAN Ai-hua WANG Dong-mei
