Plasmodesmata diversity in wheat young leaf tissues

Electron microscopic observations revealed that there were at least 4 types of plasmodesmata existed in the cell walls of wheat young leaf tissues:(1) Straight channel of plasmodesmata with an appressed endoplasmic reticulum (ER, central desmotubule);(2) “neck type” plasmodesmata, e.g. both ends of the ER-contained plasmodesma appeared to be constricted, showing a “neck region”, and even forming an “abdomen” phenomenon; (3) branched plasmodesmata with appressed ER;(4) Lastly and most interestingly, a simple plasmodesma, that only is a plasmalemma-lined channel, without ER was found, which demonstrates that the ER-contained plasmodesma is not the unique characteristic in higher plant. The plasmodesma without ER might be a more effective pathway for macromolecules intercellular transport, particularly, for the intercellular movement of protoplasm, chromatin and nucleus.