Why does high temperature decrease the photosynthetic efficiency of C3 plants more severely than that of C4 plants?

Answer and explanation

Correct answer: A. Lowers CO2 solubility vs O2 and increases RuBisCO oxygenase activity over carboxylase

  1. Step 1: With rising temperatures, the solubility of both gases decreases, but solubility decreases more rapidly than solubility.
  2. Step 2: In addition, elevated temperature induces a conformational shift in RuBisCO that increases its affinity for relative to .
  3. Step 3: Consequently, photorespiration increases substantially in C3 plants at higher temperatures, wasting fixed carbon.
  4. Step 4: C4 plants concentrate around RuBisCO via the Hatch-Slack pump, effectively preventing oxygenase activity even at high temperatures (optimum 35-45°C).
Answer
High temperature decreases the solubility of CO2 relative to O2 and increases the oxygenase affinity of RuBisCO, boosting photorespiration
Why not the others: 'High temperature directly denatures PEP carboxylase...' is incorrect because PEPcase in C4 plants is heat-tolerant with a higher temperature optimum than RuBisCO; 'High temperature prevents the photolysis of water in C3 plants only' is false because PS II water splitting functions across both C3 and C4 mesophyll; 'High temperature causes complete destruction of stomatal guard cells...' is an exaggerated, biologically inaccurate assertion.

Practise more Photosynthesis in Higher Plants.

Free questions with an explanation for every one, and full timed NEET UG mock tests.

All Photosynthesis in Higher Plants questionsTake a mock test

More Photosynthesis in Higher Plants questions

Why does high temperature decrease the… | NEET UG