Availability of Carbon Dioxide for Photosynthesis at High Altitudes: Theoretical Considerations

Contrary to current opinion, the reduction of the availability of carbon dioxide for phytosynthesis with increasing altitude, due to reduced barometric pressure, is only very small. The increased rate of diffusion of CO2 in air with altitude compensates for the effect of its lower partial pressure. The relation between CO2 availability and barometric pressure depends also on the characteristics of the plant's CO2—uptake mechanism and on the prevailing air temperature.