The mechanism of photosynthesis in plants occurs in two main stages: the light-dependent reactions and the Calvin cycle. In the light-dependent reactions, which take place in the thylakoid membranes, sunlight is captured by chlorophyll, generating ATP and NADPH while splitting water molecules to release oxygen. Subsequently, the Calvin cycle occurs in the stroma, utilizing ATP and NADPH to convert carbon dioxide into glucose. Together, these processes enable plants to harness solar energy and produce organic compounds essential for life.