Trade-offs determine plant responses to ozone pollution.

Tropospheric ozone (O3) triggers interconnected plant responses across physiological, whole-plant, and ecological scales. This review presents trade-offs as a unifying framework for understanding these responses. Stomatal closure limits both O3 entry and carbon gain, creating an avoidance-photosynthesis trade-off and influencing water relations. Resulting carbon constraints drive allocation trade-offs between growth and defense and between roots and shoots. These shifts cascade to trophic interactions, altering plant-insect and plant-microbe dynamics. In agriculture, differential sensitivity of grain biomass and nutrient accumulation produces an apparent yield-quality trade-off. This framework explains how O3 interacts with other global changes, with outcomes varying by stress intensity and plant type. Deciphering this hierarchy of interconnected trade-offs is crucial for predicting future impacts and guiding crop breeding and conservation.