Water transport in living beings can be elicited by the process of osmosis and reverse-osmosis. In the xylem of plants, three kinds of power, such as physical, osmotic and biological force, tried to apply in order to understand the sap ascent and emboli-repair mechanism. Embolim will be recovered by force of osmosis(-) or reverse-osmosis(+) in parenchyma cells of xylem, and diurnal change will be due to pressure of root and stem. The longitudinal and transverse movement of water interactively in both xylem and phloem may be explained by the model of cyclic chains like stairway. Xylem embolus can be repaired by reverse-osmosis and phloem refilled by osmosis in turn within short distance. So cyclic chains may be able to complete a water-circuit cycle up to the long distance.