Future agricultural productivity is threatened by simultaneous changes in atmospheric composition and climate, including rising CO₂, elevated tropospheric ozone, and more frequent droughts. These factors rarely occur in isolation; their interactions can strongly influence photosynthetic processes, carbon allocation, and overall crop performance. Understanding responses across scales—from cellular biochemistry to canopy-level fluxes—is essential for developing resilient crop systems capable of sustaining yields in a changing environment. Here, we focus on maize, a C₄ crop widely grown for global food and feed production.
In this study, we evaluated maize responses to combined CO₂, ozone, and drought stress under field conditions. At the leaf scale, portable gas exchange systems and biochemical assays were used to quantify Rubisco activity, electron transport rates, carbohydrate metabolism, and antioxidant enzyme function. These data were paired with measurements of stomatal behavior to assess water-use efficiency under stress. At the canopy scale, eddy covariance flux towers and remote sensing provided continuous data on carbon exchange, energy balance, and conductance across growing seasons. Because maize uses C₄ photosynthesis, its responses to elevated CO₂ and interacting stresses provide insight into how C₄ crops may perform under future climate conditions.
Our findings demonstrate that elevated CO₂ enhances photosynthetic carbon assimilation but does not fully compensate for ozone-induced reductions, particularly when drought intensifies stomatal closure and limits carbohydrate export. Some cultivars maintained photosynthetic capacity through strong antioxidant defenses and stable Rubisco function, while others exhibited large declines in canopy carbon gain.
These results underscore the importance of selecting and breeding crop varieties with combined biochemical, physiological, and structural resilience. By linking canopy-scale dynamics with underlying metabolic traits, this research highlights pathways for improving crop productivity and food security under the multifactorial stressors of future climates.
