| Abstract: | Electron microscopic observation revealed that poplar (Populus deltoides Marsh.) and winter wheat (Triticum aestivum L. cv. Seward 80004) plasmodesmatal structures significantly changed under short day (SD, 8 h light) and in winter period, and such changes differed also noticeably between these two woody and herbaceous plants. Under long day (LD, 16 h light), many plasmodesmata with strong stain appeared in the cell wall of both poplar apical buds and winter wheat young leaf tissues, and connections of cytoplasmic endoplasmic reticulum (ER) with the ER in some plasmodesmata were observed. In addition, the typical “neck type” plasmodesmata were observed in winter wheat young leaf tissues, and their central desmotubules (appressed-ER) could be clearly identified. Under SD, many poplar plasmodesmata showed only a partial structure in the cell wall and appeared to be discontinued; some plasmodesmata swelled in the mid-wall, forming the cavity, and no appressed-ER appeared. In winter wheat, however, no noticeable alterations of plasmodesmata occurred, and the plasmodesmatal structure essentially remained same as it was under LD. In winter period, poplar plasmodesmata had a similar morphology as those observed under SD, however, winter wheat manifested at least two types of significant plasmodesmatal alterations: one plugged by electron-dense materials and the other of reduced neck region compared to those under LD. The above dynamic difference of the two species plasmodesmata under SD and winter period revealed the difference of their dormancy development under those environmental conditions. |
