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Increasing crop productivity to meet burgeoning human food demand is challenging under changing environmental conditions. Since industrial revolution atmospheric CO₂ levels have linearly increased. Developing crop varieties with increased utilization of CO₂ for photosynthesis is an urgent requirement to cope with the irreversible rise of atmospheric CO₂ and achieve higher food production. The primary effects of elevated CO₂ levels in most crop plants, particularly C₃ plants, include increased biomass accumulation, although initial stimulation of net photosynthesis rate is only temporal and plants fail to sustain the maximal stimulation, a phenomenon known as photosynthesis acclimation. Despite this acclimation, grain yield is known to marginally increase under elevated CO₂. The yield potential of C₃ crops is limited by their capacity to exploit sufficient carbon. The “C fertilization” through elevated CO₂ levels could potentially be used for substantial yield increase. Rubisco is the rate-limiting enzyme in photosynthesis and its activity is largely affected by atmospheric CO₂ and nitrogen availability. In addition, maintenance of the C/N ratio is pivotal for various growth and development processes in plants governing yield and seed quality. For maximizing the benefits of elevated CO₂, raising plant nitrogen pools will be necessary as part of maintaining an optimal C/N balance. In this review, we discuss potential causes for the stagnation in yield increases under elevated CO₂ levels and explore possibilities to overcome this limitation by improved photosynthetic capacity and enhanced nitrogen use efficiency. Opportunities of engineering nitrogen …