Nitrogen fertilizer modulated the effect of drought priming on photosynthesis, antioxidant defense, nitrogen metabolism, yield in summer maize

Introduction: Post-anthesis drought stress is a major constraint on the growth and yield formation of summer maize. Although drought priming can alleviate drought stress damage, whether increased nitrogen (N) application can enhance this beneficial regulation remains unclear. Methods: This study aimed to explore the regulatory mechanisms underlying the combined effects of drought priming and N fertilizer on photosynthetic characteristics, antioxidant systems, N metabolism, root morphology, and yield formation in summer maize. Results and discussion: ) by 13.8%, 38.1%, and 32.4%, respectively, and effectively improved the chlorophyll, flavonoid, and anthocyanin indices. N fertilizer enhanced the priming-induced activation of the antioxidant system, with the N2P treatment increasing superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities by 28.9%-57.1%. Under the regulation of priming and N fertilizer, the expression of N metabolism-related genes remained at relatively high levels, leading to significantly elevated nitrate reductase (NR) activity and aboveground N accumulation. Meanwhile, root length density, root surface area density, and root dry weight density increased by 31.6%, 22.5%, and 13.9%, respectively. These coordinated improvements in physiology and morphology optimized the yield components, thus resulting in a 16.2% grain yield advantage for N2P treatment over N1D, while achieving the highest drought tolerance. Collectively, drought priming combined with N2 application effectively improved maize yield by synergistically improving N metabolism, protecting the photosynthetic system, enhancing antioxidant capacity, and promoting root architecture development. This provides an agronomic strategy to obtain stable, high-yield, and efficient resource use in summer maize in arid areas.