Explanation

Guttation refers to the exudation of liquid drops from margins and tips of the leaves throught specialized structures called hydathodes. The development of root pressure in a plant leads to positive hydrostatic pressure in xylem sap throughout the plants. Because water conducting xylem elements of a vascular bundle terminate in a hydathodes, xylem sap is forced to flow throught the hydathodes. Thus in guttation water is exuded from the leaf.