Photosynthesis is the process by which plants turn sunlight into energy, which they store in sugars and use to survive and grow. The green leaves of plants function as solar panels, absorbing sunlight that they use to start chemical reactions.
A green pigment, named chlorophyll, drives photosynthesis. This pigment gives plants their green colour.
Photosynthesis converts water and carbon dioxide into sugar and oxygen. These are substances that animals need for eating and breathing, and they are the reasons that plants and animals live in symbiosis.
Plants are not the only living things that use photosynthesis. Some bacteria and protistas, such as protozoa and red tide algae use it too. There is even a species of sea slug that incorporates algal DNA into its own, becoming capable of photosynthesis.
In hot conditions, such as those in the desert, plants can lose water through their pores. This causes some of them to shut their pores during the day to conserve water. This renders these plants incapable of absorbing the carbon dioxide they need for photosynthesis. Many plants, such as crab grass, cacti and pineapples, have adapted the photosynthesis process to their needs, using slightly different chemicals or performing the steps in different orders.