Biology [5 Mark Question Answer]

Root Pressure is the pressure exerted on the liquid contents of the cortical cells of the root, under fully turgid condition, forcing a quantity of water into the xylem vessels and through them upwards into the stem up to a certain height.
Demonstration of Root pressure:

(a) Take a well matured healthy herbaceous plant.
(b) The stem of the plant is cut a few centimeters above the base with a sharp knife and attached to a manometer through a rubber tube.
(c) After a few hours, the level of mercury rises in the manometer.
(d) This is due to the pressure created by water exuded from the cut end of the plant on account of root pressure generated due to entry of water in the root cells.

Cell wall separates the two solutions - cell sap and soil solution and is permeable which means it allows the water to enter inside the root hair cells by endosmosis.

The main root with its many branches form a network in the soil. The root hairs get entangled in the soil particles and remain in close contact with the capillary water surrounding the soil particles. The epidermal cells of root hairs have vacuoles which contain cell sap. Generally, the cell sap is more concentrated than the soil solution. As a result the water enters inside the root hair cells by endosmosis. This water dilutes the epidermal cell sap solution. Then water enters into the cortical cells by osmosis and reaches the endodermal cells and then pericycle cells. From this layer water then enters in the xylem tissue. In this way, the water is absorbed and translocated up to xylem of the root by osmosis.