A region in a cell wall where the primary wall is not overlaid by secondary thickening, through which substances can be exchanged between adjacent cells. The pit consists of a cavity, which is the area of thinning in the secondary wall, and a pit membrane, which is the primary cell wall covering the cavity. Pits usually occur in pairs. See bordered pit, primary pit, and secondary pit; see also plasmodesmata.
Subjects: Plant Sciences and Forestry.