Question

Middle lamella represent
A. Common wall between adjacent cells
B. Common membrane covering of two adjacent cells
C. Pore between adjacent cells
D. Cementing material between two adjacent cells

Answer 1

Hint: Two membranes, the middle lamella and the primary cell wall, are present in all cell walls, and several cells create an additional layer, called the secondary wall. The middle lamella acts between the primary walls of neighbouring cells as a cementing sheet.

Complete answer:
The cellulose-containing layer laid down by cells that are dividing and developing is the main wall. Primary walls are thinner and less rigid than those of cells that have stopped growing, to allow for cell wall expansion during development. A fully grown plant cell may maintain (sometimes thicken) its primary cell wall, or an additional, rigidizing layer of different composition, the secondary cell wall, may be deposited.

Some of the mechanical support of the plant as well as the mechanical properties valued in wood are responsible for secondary cell walls. In comparison to the permanent stiffness and load-bearing capability of thick secondary walls, only when the vacuoles inside the cell are filled with water to the point that they exert a turgor pressure against the cell wall are the thin primary walls capable of serving a structural, supporting function. Turgor-induced primary wall stiffening is similar to air pressure stiffening of the sides of a pneumatic tyre. A lack of turgor pressure causes the wilting of flowers and leaves to occur.
The middle lamella is a pectin-rich layer and forms the connexions of plasmodesmata between adjacent cell walls. This layer cements two neighbouring plant cells' cell walls. It is the first outermost layer formed (the middle lamella or lamellum is formed by the cell plate formed during cell division).

Hence, the correct answer is (D).

Note: While in detailed chemical composition and structural organisation, primary and secondary wall layers vary, their basic architecture is the same, consisting of high tensile strength cellulose fibres embedded in a polysaccharide and structural glycoprotein water-saturated matrix.