Drought by CO ₂ interactions in trees: a test of the water savings mechanism

Elevated atmospheric CO2 (eCa ) may benefit plants during drought by reducing stomatal conductance (gs but any 'water savings effect' could be neutralized concurrent stimulation of leaf area. We investigated whether eCa enhanced water savings, thereby ameliorating the impact on carbon and relations in trees. report leaf-level gas exchange whole-plant soil a short-term dry-down two Eucalyptus species with contrasting tolerance. Plants had previously been established for 9 to 11 months steady-state conditions ambient (aCa , half each treatment group exposed sustained 5 7 months. The lower under did not lead moisture due counteractive effect increased Nonetheless, -grown maintained higher photosynthetic rates potentials, making them less stressed dry-down, despite being larger. These effects were more pronounced xeric than mesic species, water-stressed plants. Our findings indicate that enhance plant performance lack especially conservative growth water-use strategies.