Carbon-Nitrogen Interplay Under Drought Stress: Mechanisms of Dual Limitation and Mitigation Strategies in Plants

Abstract Drought stress significantly constrains plant growth and terrestrial ecosystem productivity by disrupting the synergistic interplay between carbon (C) assimilation and nitrogen (N) cycling. This review synthesizes evidence for a multi-tiered “C–N dual limitation” feedback loop under drought conditions, driven by the following key mechanistic disruptions: (1) impaired photosynthetic C assimilation due to combined stomatal and non-stomatal limitations; (2) suppressed soil N mineralization and reduced root N uptake; (3) drought-driven shifts in microbial community structure that weaken organic N mobilization and mycorrhizal nutrient transport; and (4) a metabolic trade-off in energy allocation, whereby ATP and NADPH are diverted from growth to antioxidant defense. To unravel the complexity of this C–N imbalance, we address three pivotal issues: (1) to dissect the interactive regulation of physiological, metabolic, and molecular processes that reinforce the feedback loop; (2) to contrast the C–N coordination strategies across C3, C4, and CAM plants, linking these differences to divergent drought resilience; (3) to evaluate pathways to mitigate this limitation, ranging from the targeting of key regulatory hubs such as TOR/SnRK1 and ABA-ROS signaling, to leveraging of rhizosphere microbial ecology, and to discuss their integration into predictive models. By integrating current insights, this review presents a coherent framework for understanding plant drought resistance and proposes actionable strategies for sustainable ecosystem management in a changing climate.