Together, the epidermal and endodermal pumps push water across the root and up the xylem with a slight pressure, called root pressure, the effect of which is seen when liquid oozes from the cut stump of an herbaceous stem. Root pressure is also responsible for the droplets of water appearing early in the morning at leaf tips or on leaf margins. Such exudations are called water of guttation (Latin: gutta, “drop”) and emerge from special pores (hydathodes) evolved by certain species to rid themselves of excess dissolved salts.
