Although improving photosynthetic efficiency is widely recognized as an underutilized strategy to increase crop yields, research in this area is strongly biased towards species with C3 photosynthesis relative to C4 species. Here, we outline potential strategies for improving C4 photosynthesis to increase yields in crops by reviewing the major bottlenecks limiting the C4 NADP-malic enzyme pathway under optimal and suboptimal conditions. Recent experimental results demonstrate that steady-state C4 photosynthesis under non-stressed conditions can be enhanced by increasing Rubisco content or electron transport capacity, both of which may also stimulate CO2 assimilation at supraoptimal temperatures. Several additional putative bottlenecks for photosynthetic performance under drought, heat, or chilling stress or during photosynthetic induction await further experimental verification. Based on source–sink interactions in maize, sugarcane, and sorghum, alleviating these photosynthetic bottlenecks during establishment and growth of the harvestable parts are likely to improve yield. The expected benefits are also shown to be augmented by the increasing trend in planting density, which increases the impact of photosynthetic source limitation on crop yields.

中文翻译：

---

改善 C4 光合作用以提高最佳和次优条件下的生产力


尽管提高光合作用效率被广泛认为是一种未充分利用的提高作物产量的策略，但该领域的研究强烈偏向于具有 C3 光合作用的物种（相对于 C4 物种）。在这里，我们通过回顾在最佳和次优条件下限制 C4 NADP-苹果酸酶途径的主要瓶颈，概述了改善 C4 光合作用以提高作物产量的潜在策略。最近的实验结果表明，非胁迫条件下的稳态 C4 光合作用可以通过增加 Rubisco 含量或电子传输能力来增强，这两者也可能刺激超适温度下的 CO2 同化。在干旱、热或冷胁迫下或光合诱导过程中光合作用性能的几个其他假定瓶颈有待进一步的实验验证。根据玉米、甘蔗和高粱的源库相互作用，缓解可收获部分建立和生长过程中的这些光合作用瓶颈可能会提高产量。种植密度的增加趋势也增强了预期效益，这增加了光合源限制对作物产量的影响。