Question:

Photorespiration is favoured by

Updated On: Aug 20, 2024
  • high $O_2$ and low $CO_2$
  • low light and high $O_2$
  • low temperature and high $O_2$
  • low $O_2$ and high $CO_2$
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The Correct Option is A

Solution and Explanation

Photorespiratory loss of $CO_2$ occurs when RuBisCo starts functioning as an oxygenase instead of carboxylase under conditions of high $O_2$ and low $CO_2$. It involves three organelles chloroplast, mitochondria and peroxisomes. Half of the photosynthetically fixed carbon (in the form of RuBP) may be lost into the atmosphere through this process and no ATP formation occurs.
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Concepts Used:

Photorespiration

Photorespiration is a wasteful process in plants in which plants intake oxygen, and sunlight and release carbon dioxide and no glucose is formed. Photorespiration generally takes place when the concentration of oxygen in the leaves is very high and that of carbon dioxide is very low.

In Calvin cycle carbon dioxide fixation does not take place . Hence, instead of carbon dioxide oxygen reacts with RuBP.

Photorespiration in C3 and C4 Plants:

  • C4 plants do not undergo photorespiration due to their special mechanism to increase the CO2 level for enzyme binding.
  • In Hatch and Slack Pathway, C4 acid and oxaloacetic acid breaks down to release CO2.
  • This ensures a high concentration of intercellular CO2.
  • Thus, in C4 plants, RuBisCO is more active as a carboxylase enzyme rather than as an oxygenase.
  • This is why C4 plants have better productivity.