|PLASMODESMA... gap junctions of plants
Plasmodesmata are fine cytoplasmic strands that connect the protoplasts of adjacent plant cells by passing through their cell walls. Plasmodesmata are cylindrical in shape (about 20-40 nm in diameter) and are lined by the plasma membrane of the two adjacent cells. The endoplasmic reticulum of the two adjacent cells are connected by a narrower structure, the desmotubule, which runs through the centre of a plasmodesma.
Plasmodesmata are sheathed by a plasma membrane that is simply an extension of the plasma membrane of the adjoining cells. This raises the intriguing question of whether a plant tissue is really made up of separate cells or is, instead, a syncytium: a single, multinucleated cell distributed throughout hundreds of tiny compartments!
Plasmodesmata provide an easy route for the movement of ions, small molecules like sugars and amino acids, and even macromolecules like RNA between cells. Plasmodesmata may even enable plants to transmit signals - such as the need to mount a defense against a viral infection - from one part of the plant to another.