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.
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