Effects of low and elevated CO2 partial pressure on growth and reproduction of Arabidopsis thaliana from different elevations

Atmospheric CO₂ partial pressure may have been as low as 18 Pa during the Pleistocene and is expected to increase from 35 to 70 Pa before the end of the next century. Low CO₂ reduces the growth and reproduction of C₃ plants, whereas elevated CO₂ often increases growth and reproduction. Plants at high elevation are exposed to reduced CO₂ partial pressure and may be better adapted to the low CO₂ of the Pleistocene. We examined genotypes of Arabidopsis thaliana from different elevations for variation in growth and reproduction at the CO₂ levels of the Pleistocene, the present and the future. Genotypes exhibited limited genetic variation in the response of the production of biomass to changes in CO₂, but showed significant variation in reproductive characters. We found evidence that plants from high elevations may be better adapted to low CO₂ when considering seed number, which is an important component of fitness. Genotypes showed greater variation in the response of seed number between 35 and 20 Pa CO₂ compared to 35 and 70 Pa CO₂. We conclude that present-day C₃ annuals may have greater potential for evolution in response to the low CO₂ of the Pleistocene relative to the elevated CO₂ predicted for the future.