Underground, under every tree, there is a root system that extends two to four times further than the branches of the tree. In some trees the room system spread may be twice the height of the tree. Attached to every root are tiny root hairs. They act like miniature straws to draw up water and nutrients. That mixture is sent up the pipeline to the leaves.
Roots also receive food from the pipeline so they can grow.
Every part of the tree is involved in this system. The roots gather water. Water flows up the trunk to the leaves where it is combined with carbon dioxide and sunlight to make food. This food flows back down through the trunk to help all parts of the tree grow. If there is a microscope or magnifying glass available, show students a slide from a leaf so that they can actually see chlorophyll cells.