Nitrogen supply alleviates cold stress by increasing photosynthesis and nitrogen assimilation in maize seedlings.

Cold stress (CS) inhibits the early growth of maize, leading to reduced productivity. Nitrogen (N) is an essential nutrient that stimulates maize growth and productivity, but the relationship between nitrogen availability and cold tolerance is poorly characterized. Therefore, we studied the acclimation of maize under combined CS and N treatments. Exposure to CS caused a decline in growth and N assimilation but increased abscisic acid (ABA) and carbohydrate accumulation. The application of different N concentrations from the priming stage to the recovery period resulted in the following effects: (1) High N supply alleviated CS-dependent growth inhibition, as shown by increased biomass, chlorophyll and Rubisco contents, PSII efficiency, and carbohydrate partitioning; (2) CS-induced ABA accumulation was repressed under high N, presumably due to enhanced stomatal conductance; (3) The mitigating effects of high N on CS could be due to the increased activities of N assimilation enzymes and improved redox homeostasis. After CS, the recovery ability of maize seedlings increased under high N treatment, indicating the potential role of high N in the CS tolerance of maize seedlings.