Veins also help to support the leaf. On the underside of the leaf are small openings or pores called the stomata. The stomata serve as the lungs of the leaf allowing air to enter. The stomata allow the evaporation of water and the release of oxygen during the night. The outer layers of the leaf are covered with a waxy layer which prevents the leaf from drying out.
Leaves are green because they contain small bodies in the cells called chloroplasts.
The chloroplasts contain a green pigment called chlorophyll. This green material gives the leaf its colour. With the help of chlorophyll and energy from the sun, a leaf can change lifeless substances into food. This process is called photosynthesis. The water is gathered by the plant's roots.