Photorespiration, or "'photo-respiration'", is a process in plant metabolism. A sugar has oxygen added to it by the enzyme (RuBisCO), instead of carbon dioxide during normal photosynthesis. This process reduces efficiency of photosynthesis.
Photorespiration can occur when carbon dioxide levels are low, for example, when the stomata are closed to prevent water loss during drought. In most plants, photorespiration increases as temperature increases. Photorespiration produces no ATP and leads to a net loss of carbon and nitrogen (as ammonia), slowing plant growth.