Plasmodesmata (singular: plasmodesma) are very fine channels that pass through the cell walls of neighbouring plant cells, linking their cytoplasm. There can be thousands on a single cell.Structure
Each plasmodesma is lined by the cell surface membrane, which is continuous from one cell to the next, so the cytoplasm of the two cells is joined. Running through the centre is a narrow tube of endoplasmic reticulum called the desmotubule. Plasmodesmata are about 20 to 50 nm wide, so they are only visible with an electron microscope. They are often grouped in thin areas of the wall called pits.
Functions
• Transport: water, ions, sugars, amino acids and other small molecules can pass directly from cell to cell without crossing a membrane. The route through the cytoplasm of connected cells via plasmodesmata is called the symplast pathway.
• Communication: signalling molecules, some proteins and some RNA molecules can pass through, allowing cells to coordinate their activities, for example in development and in responses to infection.
• They link cells into a continuous living system, which is important for moving sugars into the phloem and water across the root.Example
In a root, water entering a root hair cell can move from cytoplasm to cytoplasm through plasmodesmata, across the cortex, towards the xylem. This is the symplast pathway, in contrast to the apoplast pathway through the cell walls.A drawback is that some plant viruses can spread from cell to cell through plasmodesmata.
Each plasmodesma is lined by the cell surface membrane, which is continuous from one cell to the next, so the cytoplasm of the two cells is joined. Running through the centre is a narrow tube of endoplasmic reticulum called the desmotubule. Plasmodesmata are about 20 to 50 nm wide, so they are only visible with an electron microscope. They are often grouped in thin areas of the wall called pits.
Functions• Transport: water, ions, sugars, amino acids and other small molecules can pass directly from cell to cell without crossing a membrane. The route through the cytoplasm of connected cells via plasmodesmata is called the symplast pathway.
• Communication: signalling molecules, some proteins and some RNA molecules can pass through, allowing cells to coordinate their activities, for example in development and in responses to infection.
• They link cells into a continuous living system, which is important for moving sugars into the phloem and water across the root.Example
In a root, water entering a root hair cell can move from cytoplasm to cytoplasm through plasmodesmata, across the cortex, towards the xylem. This is the symplast pathway, in contrast to the apoplast pathway through the cell walls.A drawback is that some plant viruses can spread from cell to cell through plasmodesmata.