What is the green substance in plants that is crucial for photosynthesis?

Chlorophyll is the green pigment found in the chloroplasts of plant cells, and it plays a critical role in photosynthesis. During this process, chlorophyll absorbs sunlight, primarily in the blue and red wavelengths, and transforms that light energy into chemical energy. This light energy is used to convert carbon dioxide and water into glucose and oxygen, making it essential for the survival of plants and, by extension, life on Earth.

While xanthophyll and carotene are also pigments found in plants, they do not contribute to the process of photosynthesis in the same way that chlorophyll does. Instead, they assist in other functions, such as protecting the plant from excessive light and contributing to the yellow and orange hues seen in leaves. Stomata, on the other hand, are small openings on the surfaces of leaves that facilitate the exchange of gases (like oxygen and carbon dioxide) but are not a pigment and do not perform photosynthesis directly.

Thus, chlorophyll's specific function in capturing light energy makes it the crucial substance needed for photosynthesis in plants.