Which substances are used as reactants in plant photosynthesis?

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Diagram of a tree leaf illustrating photosynthesis, with arrows showing sunlight, water, and carbon dioxide entering the leaf and sugars and oxygen being produced. A person is shown beside the tree to demonstrate the exchange of oxygen and carbon dioxide between plants and animals. — Photosynthesis Diagram of photosynthesis showing how water, light, and carbon dioxide are absorbed by a plant to produce oxygen, sugars, and more carbon dioxide.

In plant photosynthesis, the primary reactants are carbon dioxide and water.41

These substances are converted into organic products—specifically sugars such as glucose—through a series of light-dependent and light-independent (dark) reactions. The process is driven by light energy, which is captured by chlorophyll within the plant's chloroplasts.234

While the simplified chemical equation is often represented as $6 C O_{2} + 6 H_{2} O \to C_{6} H_{12} O_{6} + 6 O_{2}$ , the actual mechanism involves more complex interactions, including the use of ribulose 1,5-bisphosphate (RuBP) as a carbon dioxide acceptor during the Calvin-Benson cycle. During these reactions, water is oxidized to provide electrons and hydrogen ions, resulting in the release of oxygen as a by-product.32