Solution

A plant cell is characterised by a cellulosic cell wall. The cell walls are separated by a middle layer or middle lamella. The middle lamella is actually a cementing layer between two plant cells. It is absent on the outer surface. Middle lamella is made up of calcium and magnesium salts of pectin. Pectins are mucopolysaccharides that occur in plant cell walls. Pectic acid is polymer of D-galacturonic acid.