How do plants and trees use capillary action?

The water pressure decreases as it rises up the tree. This is because the capillary action is fighting the weight of the water. Although the xylem tube is very thin, and therefore the weight of the water is very low, it is not zero. Eventually, the effects of gravity on the water starts to equal the effects of capillary action. Scientists have found that the pressure inside the xylem decreases with the height of the tree, and similarly, the size of the redwood leaves decreases with the decrease in pressure