As water molecules from plant leaves evaporate, they attract the water molecules that are still present in the plant, aiding in the movement of water from the roots up through the stems. The water in a plant is transported from the bottom to the top by the combined effects of transpiration and capillary action.
Water molecules ascend up the cellulose tubes from the roots to the leaves because they tend to cling together (cohesion) and stick to the walls of tubes (adhesion). The water from the leaves then evaporates, aiding in the root system's ability to absorb additional water. We call this mechanism capillary action.
Water and minerals travel upward from the roots through the xylem due to a negative water potential gradient created by the evaporation of mesophyll cells in the leaves. Small perforations between vessel elements must be made to reduce gas bubbles in the xylem since they can obstruct water flow in the plant.
