Assuming that you are talking about the experiment in which it is shown that the upward movement of the water is caused by root pressure, it may be concluded that the root pressure pulled water in the xylem and that is why a change is the initial and final water level was observed. If a living plant is cut a few inches above the ground, water droplets can be observed on the stem, this is when the transpiration is very low and root pressure is pulling water and xylem is under root pressure.
