Solar Power Trees and other plants make their own food from sunlight. T e process is called photosynthesis. Photo is a Greek word that means “light.” Synthesis is a Greek word that means “putting things together.”


PHOTOSYNTHESIS


A leaf turns sunlight, water, and carbon dioxide into food and oxygen.


light energy enters leaf


water enters leaf


Food Factories Plants are food factories. T ey need sunlight, water, and carbon dioxide to make food. Carbon dioxide is a gas. It is in the air we breathe out. Plants take it in. T ey combine it with sunlight and water to make sugars and another gas called oxygen. T e sugars feeds the tree. T is happens every day. Every leaf


soaks up the sunlight and makes food for a tree. Every leaf also puts oxygen into the air. Without plants, animals would have no food to eat or air to breathe.


sugar exits leaf


oxygen is released


carbon dioxide enters leaf


Growing Up and Out As a tree grows, it gets taller and wider. Branches reach up so leaves can soak in sunlight. Roots reach out to pull in water and nutrients from the soil. A tree’s growth shows up as a ring


inside the trunk. Every year a tree gets wider as it adds another ring to its trunk.


A tree's age is refl ected in the number of rings it has.


14 NATIONAL GEOGRAPHIC EXPLORER


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