Plasmodesmata (singular ; plasmodesma) are microscopic channels which traverse the cell wlls of plant cells, and some algal cells, enabling transport and communication between them. There are two forms of plasmodesmata: primary plasmodesmata, which are formed during cell division, and secondary plasmodesmata, which can form between mature cells.
Similar structures called gap junctions, membrane nanotubes, interconnect animal cells, and stomules form between plastids in plant cells.
A typical plant cell may have between 1,000 and 100,000 plasmodesmata connecting it with adjacent cells.
Plasmodesmata Structure
Plasmodesmata is a tube linking one cell to another. Surrounding the open space of the tube is a membrane and running in the center is the desmotubule, which consists of tightly packed endoplasmic reticulum (ER). The ER is continuous between the two cells. Between the desmotubule and the membrane is the cytoplasmic sleeve, where most transfer of molecules occurs. The sleeve contains various structures, such as actin and myosin, which provide contractile forces that aid in transport.
Plasmodesmat Function
Plasmodesmata facilitate the movement of molecules between cells, ranging from small photosynthetic products to large proteins and mRNA. In vascular tissue, plasmodesmata are crucial for the movement of nutrients. They are also crucial during development because, unlike animal cells, plant cells do not move. The correct expression of genes both temporally and spatially is therefore important. While plant cells, like animal cells, are capable of receptor-ligand interactions to signal other cells, plasmodesmata offer direct contact. In addition, the size of the sleeve differs in different cell types and plant tissues. Plasmodesmata are therefore an active cell component in intercellular transport, during development and in the mature tissue.
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