photorespiration

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photorespiration A light-activated type of respiration that occurs in the chloroplasts of many plants. It differs biochemically from normal (dark) respiration in that it involves glycolate metabolism (see GLYCOLATE CYCLE). It is a process that is wasteful of both carbon dioxide and energy, and those plants in which it occurs have high carbon dioxide compensation points. It occurs only at very low rates in C4 plants which consequently have lower compensation points and greater photo-synthetic efficiency. Its biological function is not clearly understood.

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