Cell wall differentiations
Although the cell wall of the plant cell is very resistant and thick, it is permeable, since it has to allow the passage of water and dissolved substances. They have some differentiations that allow this exchange:
- The pits. They are thin areas of the cell wall, formed by the middle lamina and a very thin primary wall. The pits of two adjacent cells are usually close together.
- Plasmodesmata. They are very fine cytoplasmic ducts that communicate with neighboring cells, which pass through cell walls. The plasma membrane of each cell communicates with the neighboring cell through the plasmodesmata. A tube continuation of the endoplasmic reticulum appears in the center of the plasmodesmata.