- A Mitochondrial respiration reaches its absolute maximum measured rate
- B Photosynthesis rate equals respiration rate (net gas exchange = 0)
- C Guard cells fully close the stomatal pore, halting all gas exchange
- D Ambient temperature reaches the optimum for Rubisco carboxylase activity
Correct answer: B. Photosynthesis rate equals respiration rate (net gas exchange = 0)
Explanation: Compensation point: light intensity at which CO2 fixed by photosynthesis = CO2 released by respiration. Net gas exchange is zero.
Concept context
Light reactions, the Calvin cycle, C3/C4/CAM pathways, photorespiration, and factors affecting the rate of photosynthesis. One of the highest-yield NEET chapters.