Question

what is photorespiration?

Answer 1

It is the process in which many plants take oxygen and give out some carbon dioxide ,opposite to the pattern of photosynthesis.

Answer 2

Answer:

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what is photorespiration___??

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Photorespiration is a process which involves loss of fixed carbon as CO, in plants in the presence of light It is initiated in chloroplasts. This process does not produce ATP or NADPH and is a wasteful process.

Photorespiration occurs usually when there is high concentration of oxygen. Under such circumstances, RuBisCO, the enzyme that catalyses the carboxylation of RuBP during the first step of Calvin cycle, functions as an oxygenase. Some O, does bind to RuBisCO and hence CO, fixation is decreased. The RuBP binds with O₂ to form one molecule of PGA (3C compound) and phosphoglycolate (2C compound) in the pathway of photorespiration. There is neither the synthesis of sugar, nor of ATP. Rather, it results in the release of CO₂ with the utilisation of ATP. It leads to a 25 percent loss of the fixed CO₂. O, is first utilized in chloroplast and then in peroxisomes.

Photorespiration or C₂ cycle involves three organelles viz., chloroplast, peroxisomes and mitochondria. Loss of CO2 occurs in mitochondria.

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In C4 plants, photorespiration does not occur. This is because these plants have a mechanism that increases the concentration of CO2 at the enzyme site. During the C, pathway, when the C, acid from the mesophyll cells is broken down in the bundle sheath cells, it releases CO, - this results in increasing the intracellular concentration of CO2. This in turn, ensures that the RuBisCO functions as a carboxylase minimising the oxygenase activity.

Thus, the productivity and yields are better in C, plants as compared to C, plants. In addition, the C, plants show tolerance to higher temperature also.