As you can see the increasing suberization in older parts of the root prevent water uptake through the endodermis. Indeed water intake is limited to the zone just behind the elongation area at the root tips. However, the important point here is that the endodermis has transport proteins that allow the root to accumulate ions by active transport. The pressure that develops at the bottom of the column of xylem can push water up that column. The total pressure that roots can provide this way is about 0.05 to 0.5 MPa depending on weather conditions.
Root pressure is also sometimes visible on leaves.
Under conditions of high humidity, cool temperature, and low light exposure root pressure can push xylem fluids through leaf mesophyll and out some larger pores in the leaves called hydathodes . Thus on a cool morning as you walk across the grass you notice a drop of liquid on the tip of each blade. You may have thought this was dew, but because it is on the upward pointing tip, you realize that this cannot be so. The process by which this exudes is called guttation and it is driven by root pressure. Capillarity allows water to climb up the xylem We have already discussed this in a previous lecture.