How a Cactus Makes Food

Lucy takes Amir to an area with cactus plants. The cactuses do not have leaves. "Cactuses grow in the desert. There is a lot of sunlight but not a lot of water," says Lucy. "Why doesn’t a cactus have leaves?" asks Amir. "It is hot in the desert. As the Sun warms the air, water escapes from the leaves. A cactus doesn’t have leaves, so water can’t escape," says Lucy.

"How does a cactus make food without leaves?" Amir asks. "A cactus makes food differently than other plants," says Lucy. "The cactus has chlorophyll like other plants. But cactuses make food in their stems because they have no leaves. This is why a cactus stem is green. Food is made in the cactus stem."

"The roots of a cactus spread out very wide," says Lucy. "They are not deep in the ground. Roots can take in more water and nutrients to the cactus faster. The water is stored in the stem. Most cactus plants are covered with wax and prickly spines. These spines also collect rainwater that is stored in the cactus."

"A cactus has small openings like a leaf to let in carbon dioxide. A cactus only lets in carbon dioxide at night when it is cool. If the cactus lets in carbon dioxide during the hot day, too much water would escape. The openings of the cactus are like windows. They open at night to let in the carbon dioxide. They close during the day to keep carbon dioxide and water in," says Lucy.

"A cactus stores carbon dioxide until the Sun comes up," says Lucy. "Energy from sunlight goes into the cactus stem. The cactus uses sunlight, water and carbon dioxide to make sugar and oxygen. The cactus uses the sugar as food for energy to grow bigger. Flowers bloom and seeds form on the cactus."

Lucy holds up a small plant with thick leaves. "These are succulents. A lot of people buy these plants at the garden center," Lucy says. "These plants store water like cactus plants. They make food the same way too. People like to put these in their homes. They are easy to take care of. They don’t need a lot of water or sunlight."

Lucy cuts a leaf off the succulent plant. "These plant parts can regrow," says Lucy. "A new plant will grow from a cut leaf or stem." Lucy puts the cut leaf in soil with water. Roots will begin to grow. The leaf will take sunlight, water and carbon dioxide and change them into sugar and oxygen. The plant part will grow into a bigger plant.

"We have seen many different plants at the garden center today," says Lucy. "All of the plants need sunlight, water and carbon dioxide. Plants make their own food through photosynthesis. I want to take you to one last area of the garden center. There you will see plants that need something different to help them make food."