Plant Cell Wall

Plant cell walls are layered structures, and each layer has a distinct composition and role. The middle lamella, made chiefly of calcium pectate, lies between the walls of two adjacent cells and acts as the cement that binds neighbouring cells together, a point emphasised in NCERT Class 11, Chapter 8 (Cell: The Unit of Life). The primary wall is incorrect here because it is the layer formed first, capable of growth, and lies inside the middle lamella rather than between two cells. The secondary wall is deposited later toward the inner side of the primary wall in mature cells and provides mechanical strength, not cementing. Plasmodesmata are cytoplasmic bridges that pass through the walls to connect the living protoplasts of adjacent cells, so they are channels for communication, not adhesive layers. A structural check confirms the answer: only a layer positioned exactly between two cells and rich in sticky calcium pectate could serve as the binding cement, and that role belongs to the middle lamella.