The primary purpose of photosynthesis for plants is to convert light energy into chemical energy stored in glucose. During this process, plants absorb sunlight using chlorophyll in their leaves and convert carbon dioxide and water into sugars and oxygen. This conversion not only fuels the plant's growth and metabolism but also serves as the basis for the food chain, providing energy for herbivores and, subsequently, carnivores. Additionally, photosynthesis plays a critical role in regulating atmospheric CO2 levels, thus contributing to global climate stability.