The leaf can be seen as a factory driven by energy trapped from sunlight in the process called photosynthesis. The leaf absorbs carbon dioxide from the atmosphere, which combined with water and nutrients absorbed by the root are split to form organic matter, glucose. It is the glucose on which the tree feeds. The sugar is transported through stems and branches and transformed to new wood, new roots, new leaves, flowers and fruits. All that the tree needs to grow and generate.
Photosynthesis is a condition for all animal life on earth.
T rees and shrubs have perennial, woody stems. In stems and branches 2 pipelines exist, where liquids flow between the different parts of the tree. In the one, called the vessels, water and nutrients are brought to the leaves. This transport takes place in the outer wood, the sapwood. The other system, called the phloem, brings sugar from the leaves to branches and stems where it is used for growth and defence.