Present CO2 concentration in atmosphere is limiting for:

C4 plants show saturation at about 360 µlL-1 while C3 responds to increased CO2 concentration and saturation is seen only beyond 450 µlL-1. Thus, current availability of CO2 levels is limiting to the C3  plants. Maize, sorghum and sugarcane are C4 plants while tomato is a C3 plant.