Plant Responses to Increased Carbon Dioxide

Rising atmospheric carbon dioxide (CO 2 ) enhances carbon uptake in C 3 plants and reduces stomatal conductance in C 3 and C 4 plants. Even though leaf N declines, RuBisCO activity increases so the photosynthetic rate rises as does photosynthetic N use efficiency. The responses show high variability, and while the magnitude of this “fertilization” effect appears to be confounded with experimental conditions. Growth of C 3 plants increased by up to 25% and grain yield somewhat less. C 3 plants are more responsive that C 4 plants and legumes more responsive than grasses. Photosynthetic acclimation to high CO 2 constrains the response of current genotypes. Improved understanding of plant N dynamics and fine and cause of RuBisCO coupled to balancing sink numbers is the basis of developing crops for a carbon rich future. To do so require screening of large numbers of genotypes under high [CO 2 ] and then exploit those traits using modern biotechnology tools. This is to be done against the other abiotic challenges of drought and thermotolerance, as well as responding to a host of new biotic challenges thrown up by changing global climates.