Photorespiration

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.

Photorespiration Media

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  Simplified photorespiration cycle
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  Simplified photorespiration and Calvin cycle
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  PhotorespirationFrom left to right: chloroplast, peroxisome, and mitochondrion

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  Oxygenase activity of RuBisCO

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  Maize uses the C4 pathway, minimizing photorespiration
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  Overnight graph of Template:CO2 absorbed by a CAM plant

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  In C2 plants, the mitochondria of mesophyll cells have no glycine decarboxylase (GDC).