What is photorespiration?
Photorespiration involves a complex network of enzyme reactions that exchange metabolites between chloroplasts, leaf peroxisomes and mitochondria.
It refers to a process in plant metabolism where the enzyme RuBisCo oxygenates RuBP, causing some of the energy produced by photosynthesis to be wasted. Photorespiration occurs when the carbon dioxide levels inside a leaf become low. This happens on hot dry days when a plant and s forced to close its stomata to prevent excess water loss.
Photorespiration may be necessary for the assimilation of nitrate from the soil. The photorespiration pathway influences a wide range of processes from bioenergetics, Photosystem II functions, and carbon metabolism to nitrogen assimilation and respiration.
It is also a major source of hydrogen peroxide in photosynthetic cells. Through hydrogen peroxide production and pyridine nucleotide interactions , photorespiration makes a key contribution to cellular redox homeostasis. In doing so it influences multiple signalling pathways, in particular, those that govern plant hormonal responses controlling growth, environmental and defense responses, and programmed cell deaths.
Although photorespiration is greatly reduced in C4 species, it is still an essential pathway.