CO₂ compensation point
The carbon dioxide concentration at which a leaf's photosynthetic uptake equals its carbon loss through respiration and photorespiration, producing zero net exchange.
At the carbon dioxide compensation point, the carbon taken up by photosynthesis balances the carbon released by respiration and photorespiration Photorespiration A carbon-recycling pathway initiated when Rubisco reacts with oxygen instead of carbon dioxide, consuming energy and releasing some previously fixed carbon. . Gas exchange at the leaf is zero even though all of those processes continue.
The value is not one universal concentration. It varies with photosynthetic pathway, temperature, light, leaf age, and other conditions. C3 plants generally have a higher compensation point than C4 plants because C3 photosynthesis loses more carbon through photorespiration.