Abstract
Contents 34 I. 34 II. 36 III. 37 IV. 37 V. 38 38 References 38 SUMMARY: Characterizing plant responses to past, present and future changes in atmospheric carbon dioxide concentration ([CO(2) ]) is critical for understanding and predicting the consequences of global change over evolutionary and ecological timescales. Previous CO(2) studies have provided great insights into the effects of rising [CO(2) ] on leaf-level gas exchange, carbohydrate dynamics and plant growth. However, scaling CO(2) effects across biological levels, especially in field settings, has proved challenging. Moreover, many questions remain about the fundamental molecular mechanisms driving plant responses to [CO(2) ] and other global change factors. Here we discuss three examples of topics in which significant questions in CO(2) research remain unresolved: (1) mechanisms of CO(2) effects on plant developmental transitions; (2) implications of rising [CO(2) ] for integrated plant-water dynamics and drought tolerance; and (3) CO(2) effects on symbiotic interactions and eco-evolutionary feedbacks. Addressing these and other key questions in CO(2) research will require collaborations across scientific disciplines and new approaches that link molecular mechanisms to complex physiological and ecological interactions across spatiotemporal scales.