Root pressure

As ions are actively transported into the xylem of the root, water follows and builds up a positive pressure inside the xylem called root pressure.
Root pressure is best seen at night and early morning, when evaporation is low.
Under these conditions excess water is pushed out as droplets through special openings (hydathodes) near the tips of grass blades and the leaf margins of many herbaceous plants.
This loss of water in liquid form is called guttation.
Transpiration is loss of water as vapour and it creates a pull, not a push.
Hence guttation is the result of root pressure.