As various ions from the soil are actively transported into the vascular tissues of the roots, water follows its potential gradient and increases the pressure inside the xylem and this positive pressure is called root pressure.
Loss of water in its liquid phase is known as guttation.
Root pressure provide a modest push in the overall process of water transport and re-establish the continuous chains of water molecules in the xylem which often break under the enormous tensions created by transpiration.
Root pressure does not account for the majority of water transport and hence most plants meet their need by transpiratory pull.
Water is mainly ‘pulled’ through the plant, and that the driving force for this process is transpiration from the leaves, which is referred to as the cohesion-tension-transpiration pull model of water transport.
Most of it is lost through the stomata in the leaves and this water loss is known as transpiration.