Photosynthesis occurs in the leaves. This is a process in which sunlight, water, and carbon dioxide are converted, or changed, into food for the plant. The trunk of a canopy tree is a transport , or travel, system. Food is transported from the leaves throughout the tree so that it can be properly nourished , or fed. We have veins in our bodies, too.
Blood is transported through our veins.
Our blood carries oxygen, food and other things we need to all parts of our bodies, just like veins in the tree transport the things that it needs to all of its different parts. The soil on a rainforest floor is shallow and sandy. There are frequent and heavy downpours in the rainforest. Also, winds can be quite strong in the canopy layer. A rainforest tree, therefore, has quite a job of staying upright.