With the help of a labelled diagram, describe the structure of root-hair.

Answer: [Diagram: a cell of the epiblema (piliferous layer) whose outer wall is drawn out into a long tube. Labels: cell wall (outer pectic layer, inner cellulose layer), plasma membrane, thin lining of cytoplasm, nucleus near the tip, large central vacuole with cell sap, soil particles with water film around the hair.]

• A root hair is a tubular, unicellular outgrowth of an epiblema cell in the root-hair zone, just behind the zone of elongation.
• It is about 1 to 10 mm long and about 10 µm wide; it is short-lived (a few days to weeks) and new ones keep forming.
• The cell wall is thin and freely permeable: the outer layer is of pectin (calcium pectate) which makes it sticky so it clings to soil particles, and the inner layer is of cellulose.
• Inside the wall is the selectively permeable plasma membrane, a thin layer of cytoplasm with the nucleus, and a large central vacuole filled with cell sap of high osmotic pressure.
• Root hairs greatly increase the absorbing surface and absorb water and minerals from the soil by osmosis and diffusion.