Question:

Photorespiration is a prominent feature of plants having

Updated On: Jul 28, 2022
  • C3C_3 cycle
  • C4C_4 cycle
  • aerobic respiration
  • none of these
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The Correct Option is A

Solution and Explanation

Photorespiration refers to oxidation of glycolate. It is produced during glycolate metabolism of photosynthesis and occurs in three organelles peroxisomes, mitochondria and chloroplast. Hence possible only in green parts of plant. Photorespiration occurs only in C3C_3 plants because at high temperature and high oxygen concentration RuBPRuBP carboxylase is changed to RuBPRuBP oxygenase. Photorespiration is absent in C4C_4 plants because Rubisco and other Calvin cycle enzymes are present only in bundle sheath cells, and CO2CO_2 concentration in those cells is maintained too high for O2O_2 to compete with CO2CO_2. Temperature is also low in bundle sheath cells of C4C_4 plant.
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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.