Photosynthesis

Photosynthesis

Plants need sunlight. Houseplants lean toward the Sun, and if they do not get enough light they wither and die. Plants use sunlight to make their food. This process is called photosynthesis.

Photosynthesis is a scientific word made up from Greek words. These words mean “putting things together using light.”

Inside plants’ leaves, light causes air and water to combine to make new chemicals. These chemicals are food for the plants.

FOOD FACTORIES

In most plants, photosynthesis takes place mainly in the leaves. Like other living things, plants are made up of tiny cells. The cells in a plant’s leaves contain even smaller, disc-shaped parts called chloroplasts. Chloroplasts are the food factories where photosynthesis happens. A leaf the size of your little fingernail contains more than 10 million of them.

Chloroplasts contain a chemical called chlorophyll, which is bright green. Chlorophyll gives plants their green color and makes photosynthesis work.

THREE INGREDIENTS

For photosynthesis to work, the chloroplasts need to collect three ingredients: sunlight, air, and water. Sunlight shines on the leaf, and the green chlorophyll inside the chloroplasts soaks it up. Air enters the leaf through tiny holes in the leaf’s surface, called stomata. Water is sucked from the ground by the plant’s roots. It travels through tubes in the stem or trunk to the leaves.

When all three ingredients are present inside the chloroplasts, a chemical reaction takes place. The reaction takes place between a gas in air called carbon dioxide and hydrogen, a part of water. Sunlight causes these two to combine and make new chemicals called carbohydrates. Carbohydrates are plant food. Plants use these chemicals to live and grow.

THE KEY TO LIFE

Photosynthesis is not just important for plants—it is the key to life for all of us. Plants use photosynthesis to make food. We eat the leaves, roots, fruits, and seeds of plants. Spinach and lettuce are leaves. Potatoes and carrots are roots. Tomatoes and apples are fruits. Nuts are seeds. If you eat beef, lamb, or other meat, you still depend on plants. Meat comes from cows, sheep, and other animals that feed on plants.

In this way, energy from the Sun is passed on through all the different living things on Earth. If it were not for photosynthesis, plants would not grow. There would be nothing for animals to eat, so they would not exist either.

BREATHABLE AIR

Photosynthesis also produces a gas, oxygen. Plants release oxygen into the air. Humans and other animals need oxygen to live. We breathe in the oxygen produced by plants during photosynthesis.