- botany the stage of photosynthesis during which light energy is absorbed by chlorophyll and transformed into chemical energy stored in ATPCompare dark reaction
- Any of the chemical reactions that take place during the first stage of photosynthesis and require the presence of light. During the light reactions, energy captured from light by chlorophyll and its accessory pigments drives the production of ATP, the source of energy that is later used to drive the production of carbohydrates. Compare dark reaction. See more at photosynthesis.
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