Explain the process of absorption of water by the root hair and movement of water in xylem.

Explanation

1) The soil water is an extremely dilute solution of salts, more dilute than that of the cell sap in the root hair.
2) Therefore water will pass into the vacuole of the root hair by osmosis.
3) The entry of water dilutes the contents of the root hair vacuole so that it becomes weaker than its neighbour.
4) Therefore water passes into the neighbouring cell which in turn becomes diluted, finally water enters the xylem vessels.
5) As there are vast numbers of root hairs and root cells involved, a pressure in the xylem vesels develops which forces the water upwards.
6) This total pressure is known as root pressure which is responsible for movement of water in xylem.
7) The water which passed into the xylem vessels forms a continuous system of tubes through root and stem itno the leaves.
8) The evaporation of water creates the main pull from above root pressure gives a variable and minor push from below.