PubMed · 2026-01-01
Plants universally reduce the number of leaf pores (stomata) as CO₂ levels rise, regardless of whether they evolved in high or low CO₂ environments. However, local stressors like heat and low humidity can override this pattern, complicating predictions about how vegetation will respond to a CO₂-rich future.
Stomatal frequency decreased with rising CO₂ (30 vs. 42 Pa) in all tested C₃ plants, regardless of their CO₂ acclimation history
Plants grown at reduced CO₂ (~30 Pa) developed smaller stomatal apertures than those at ambient CO₂ (~40 Pa), and also produced less above-ground biomass
No significant difference in stomatal frequency was found between plants naturally acclimated at 2,970 m altitude versus 540 m, suggesting local environmental factors (temperature, humidity) can mask the CO₂ signal