Department of Primary Industries, Biosciences Research Division, Grains Innovation Park , Horsham, VIC, Australia.
Front Plant Sci. 2012 Jul 19;3:162. doi: 10.3389/fpls.2012.00162. eCollection 2012.
Increasing crop productivity to meet burgeoning human food demand is challenging under changing environmental conditions. Since industrial revolution atmospheric CO(2) levels have linearly increased. Developing crop varieties with increased utilization of CO(2) for photosynthesis is an urgent requirement to cope with the irreversible rise of atmospheric CO(2) and achieve higher food production. The primary effects of elevated CO(2) levels in most crop plants, particularly C(3) 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 CO(2). The yield potential of C(3) crops is limited by their capacity to exploit sufficient carbon. The "C fertilization" through elevated CO(2) 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 CO(2) 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 CO(2), 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 CO(2) levels and explore possibilities to overcome this limitation by improved photosynthetic capacity and enhanced nitrogen use efficiency. Opportunities of engineering nitrogen uptake, assimilatory, and responsive genes are also discussed that could ensure optimal nitrogen allocation toward expanding source and sink tissues. This might avert photosynthetic acclimation partially or completely and drive for improved crop production under elevated CO(2) levels.
在不断变化的环境条件下，提高作物生产力以满足人类不断增长的粮食需求具有挑战性。自工业革命以来，大气中的二氧化碳水平呈线性增长。开发能够更有效地利用二氧化碳进行光合作用的作物品种，是应对大气中二氧化碳不可逆转上升并实现更高粮食产量的紧迫要求。大气中二氧化碳水平升高对大多数作物（尤其是 C3 作物）的主要影响包括生物量积累增加，尽管净光合作用速率的初始刺激只是暂时的，而且植物无法维持最大刺激，这种现象称为光合作用适应。尽管有这种适应，但在高 CO2 水平下，谷物产量已知会略有增加。C3 作物的产量潜力受到其利用足够碳的能力的限制。通过升高 CO2 水平进行的“C 施肥”有可能用于大幅提高产量。Rubisco 是光合作用的限速酶，其活性在很大程度上受到大气 CO2 和氮供应的影响。此外，维持 C/N 比对于植物的各种生长和发育过程至关重要，这些过程决定着产量和种子质量。为了最大限度地利用升高的 CO2 的好处，提高植物氮库将是必要的，这是维持最佳 C/N 平衡的一部分。在这篇综述中，我们讨论了在高 CO2 水平下产量增长停滞的潜在原因，并探讨了通过提高光合作用能力和增强氮利用效率来克服这一限制的可能性。还讨论了工程氮吸收、同化和响应基因的机会，这可以确保最佳的氮分配，以扩大源和汇组织。这可能部分或完全避免光合作用适应，并在高 CO2 水平下促进作物生产的改善。
