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 synthesized 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 tradeoff in energy allocation, whereby Adenosine Triphosphate (ATP) and Nicotinamide Adenine Dinucleotide Phosphate Hydrogen (NADPH) are diverted from growth to antioxidant defense. To unravel the complexity of this C-N imbalance, we addressed 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 Crassulacean Acid Metabolism (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.

Key words: drought, photosynthesis, nitrogen transformation, carbon fixation, carbon–nitrogen dual limitation