Botany · Ch 14 — Respiration
Compensation Point
Compensation Point
At dawn and dusk, when sunlight is too weak to drive photosynthesis at full speed, a plant reaches a moment where the rate of CO2 released by respiration is exactly matched by the rate of CO2 being fixed in photosynthesis -- at this instant there is no net gas exchange with the environment at all, and this balance point is called the compensation point. Equivalently, at the compensation point the oxygen released by photosynthesis exactly equals the oxygen being consumed by respiration. Two related types of compensation point are recognised, based on which variable is being tracked: the CO2 compensation point and the light compensation point. The CO2 compensation point differs sharply between photosynthetic types -- C3 plants typically compensate somewhere between 40 and 60 ppm (parts per million) of ambient CO2, while the more efficient C4 pla …
What this figure shows. A graph plotting carbohydrate balance against time of day (hours), showing the rising-and-falling curve of photosynthesis rate crossing the roughly flat line of respiration rate; the crossing point, where the two rates are equal, is marked as the …