Question

Why do c4 plants show lower net photosynthesis at higher co2 concentrations?

Answer 1

C4 photosynthesis has several distinct properties that enable the capture of CO2 and its concentration near Rubisco, so as to reduce the oxygenase activity of Rubisco, and hence the rate of photosynthesis is also decreased.

The response of C3 species to increased carbon dioxide may be more positive than that of C4 species because photosynthetic rate of C3 species increases by doubled carbon dioxide. However, in C4 species, the photosynthesis is nearly saturated under ambient carbon dioxide. In C4 species, the positive effect of increased carbon dioxide on photosynthesis may be pronounced under drought conditions.