Photorespiration
A carbon-recycling pathway initiated when Rubisco reacts with oxygen instead of carbon dioxide, consuming energy and releasing some previously fixed carbon.
Rubisco RuBisCO The enzyme that begins carbon fixation by adding carbon dioxide to RuBP. It can also react with oxygen, initiating photorespiration. sometimes oxygenates RuBP instead of carboxylating it. The resulting compound cannot continue through the Calvin cycle and must be recycled through photorespiration, a pathway spanning chloroplasts, peroxisomes, and mitochondria.
Recycling recovers part of the carbon but consumes energy and releases carbon dioxide, lowering net photosynthesis. Photorespiration also participates in metabolic balance and stress responses, so it is not simply an inactive mistake.
The oxygenation reaction becomes more competitive at higher temperatures and lower carbon dioxide availability. C3 plants such as cannabis experience more photorespiration than plants with carbon-concentrating C4 or CAM pathways.