Individual and Interactive Effects of Elevated Ozone and Temperature on Plant Responses

From the preindustrial era to the present day, the tropospheric ozone (O-3) concentration has increased dramatically in much of the industrialized world due to anthropogenic activities. O-3 is the most harmful air pollutant to plants. Global surface temperatures are expected to increase with rising O-3 concentration. Plants are directly affected by temperature and O-3. Elevated O-3 can impair physiological processes, as well as cause the accumulation of reactive oxygen species (ROS), leading to decreased plant growth. Temperature is another important factor influencing plant development. Here, we summarize how O-3 and temperature elevation can affect plant physiological and biochemical characteristics, and discuss results from studies investigating plant responses to these factors. In this review, we focused on the interactions between elevated O-3 and temperature on plant responses, because neither factor acts independently. Temperature has great potential to significantly influence stomatal movement and O-3 uptake. For this reason, the combined influence of both factors can yield significantly different results than those of a single factor. Plant responses to the combined effects of elevated temperature and O-3 are still controversial. We attribute the substantial uncertainty of these combined effects primarily to differences in methodological approaches.