Elevated CO₂ concentration regulate the stomatal traits of oilseed rape to alleviate the impact of water deficit on physiological properties

There is a limited understanding of how stomatal distribution and structure affect photosynthesis under elevated CO₂ concentrations (e[CO₂]) and variable soil water environments. This study investigated the effects of e[CO₂] on stomatal morphology and distribution, gas exchange and growth parameters of oilseed rape plants under water deficit [soil moisture decreased from 80% field capacity (FC) (W; full irrigation) to 60% FC (D1), 40% FC (D2), and < 35% FC (D3)] and re-watering conditions in growth chambers with [CO₂] controlled at 400 µmol mol⁻¹ (a[CO₂]) or 800 µmol mol⁻¹ (e[CO₂]). e[CO₂] had a strong CO₂ fertilization effect on the net photosynthetic rate (A_n) and growth of plants under water deficit. Under a[CO₂], stomatal density and aperture on the adaxial leaf surface increased when soil moisture decreased from W to D1, while the stomatal aperture and regularity of the spatial distribution pattern of stomata decreased with decreasing soil moisture. Stomatal conductance (g_s) were 47.1% and 26.1% capacity of anatomically determined maximum anatomical conductance (g_smax) with W under a[CO₂] and e[CO₂], respectively. e[CO₂] enhanced plant recovery after re-watering through modifying stomatal traits. This study offers insights into the trade-off between stomatal traits and gas exchange for adapting plants to future climates.