[poweramps]

C3 plants will respond to increase in ambient CO2 during daytime. This prevents to a certain degree photo-respiration especially if under conditions where stomata are partially closed (Ribulose bisphosphate + O2 = phosphoglycolate instead of RuBP + CO2 = phosphoglycerate). This is a common practice for some crops grown in greenhouses. C4 plants are adapted to high heat and will not benefit much from increase in CO2 since they incorporate CO2 via another pathway and they create their own CO2 rich environment in the photosynthetic cell. CAM plants fix CO2 at night, and close their stomata during daytime.

If we consider all living things with mitochondria, then they do do aerobic respiration, ie there is a need to produce ATP with O2 as the final electron acceptor. Just that in plants, the output O2 is more than enough to support the respiration.