The products of the light reactions of photosynthesis, ATP and XADPH, are used forth’ reduction of CO., to carbohydrates by a series of reactions in the soluble phase or stroma chloroplasts. These carbon reduction reactions are catalyzed by a number of enzymes also pr in the chloroplast stroma.
These stroma reactions are long thought to be independent of light an’ as a consequence, were referred to as the dark reactions of photosynthesis. However, it is no established without any doubt that some of the enzymes of the carbon reduction reactions a~ regulated by light.
In light, these enzymes become activated and catalyze the reactions. But i darkness, they become inactivated and lost their capacity to catalyze the steps of carbon reductio: reactions.
Therefore, C02 reduction reactions are not independent of light and naming th: biosynthetic phase or carbon reduction reactions as dark reaction (or dark phase) is misleading But for historical reasons and for the easy of discussions of the steps of photosynthesis, the ter dark reactions and light reactions are still used in test books. But we should remember her that some steps of’light reactions’ are independent of light while some steps of’dark reactions’a dependent upon light.