光呼吸作用-Photorespiration是所有行光合作用的细胞（该处“细胞”包括原核生物和真核生物，但并非所有这些细胞都能运行完整的光呼吸）在光照和高氧低二氧化碳情况下发生的一个生化过程。它是光合作用一个损耗能量的副反应。
Today, we’re talking about plants and the mystery of photorespiration, which is actually diametrically opposed to photosynthesis. It is the process by which plants use light to convert carbon dioxide and water into the sugars that fuel the plant，right？ Right，Well, during photorespiration plants use light energy to consume oxygen and release carbon dioxide and water. So photorespiration undoes the work of photosynthesis？ At least part of it，so under present atmospheric conditions, plants lose about twenty-five percent of the energy that they capture through photosynthesis to photorespiration. One hypothesis is that photorespiration had a role in early evolution, when there was more carbon dioxide in the air. Another explanation is that plants use photorespiration to slow down photosynthesis under certain stressful conditions, like intense light, so that the photosynthetic apparatus doesn’t get damaged. Given all the mystery surrounding this process, some scientists even began working on genetically engineering crop plants to minimize photorespiration. But one study suggests that photorespiration is actually important to plants after all. Researchers at UC Davis showed that photorespiration enables a plant to convert inorganic nitrogen into a form of nitrate that’s needed for plant growth. This helps explain why plants have trouble growing in conditions with low oxygen and high carbon dioxide, which inhibit photorespiration.