Water mostly enters a tree through the roots by osmosis and any dissolved mineral nutrients will travel with it upward through the inner bark’s xylem (using capillary action) and into the leaves. These traveling nutrients then feed the tree through the process of leaf photosynthesis. This is a process that converts light energy, usually from the Sun, into chemical energy that can be later released to fuel an organisms’ activities including growth.
Trees supply leaves with water because of a decrease in hydrostatic or water pressure into upper, leaf-bearing parts called crowns or canopies. This hydrostatic pressure difference “lifts” the water to the leaves. Ninety percent of the tree’s water is eventually dispersed and released from leaf stomata.
This stoma is an opening or pore that is used for gas exchange. They are mostly found on the under-surface of plant leaves. Air also enters the plant through these openings. The carbon dioxide in the air entering the stoma is used in photosynthesis. Some of the oxygen produced is used in respiration through evaporation, into the atmosphere. That beneficial loss of water from plants is called transpiration.