University of Tabriz Journal of Plant Physiology and Breeding 2008-5168 16 1 2026 02 01 Enhancement of antioxidant defense and alleviation of oxidative stress in proso millet (Panicum miliaceum L.) using rice bran-coated urea under heat conditions 55 73 21278 10.22034/jppb.2026.70780.1403 EN Shurooq Abbas Department of Plant Eco-Physiology, University of Tabriz, Tabriz, Iran. Sirous Hassannejad Department of Plant Eco-Physiology, University of Tabriz, Tabriz, Iran. Soheila Porheidar Ghafarbi Dryland Agricultural Research Institute, Agricultural Research, Education, and Extension Organization (AREEO), Maragheh, Iran. 0000-0003-0789-2534 Journal Article 2025 12 18 <strong>Objective:</strong> Heat stress triggers overproduction of reactive oxygen species, leading to oxidative damage and crop yield loss. This study investigated the efficacy of rice bran-coated urea in modulating the antioxidant defense system and mitigating oxidative membrane damage in proso millet (<em>Panicum miliaceum</em> L.) under field heat stress.<br /><strong>Methods:</strong> A two-year field experiment evaluated uncoated urea, rice bran-coated urea, gypsum-coated urea, and cement-coated urea at four nitrogen rates (0, 60, 80, and 120 kg urea ha^-¹) under optimal (spring) and heat stress (summer) conditions. The experiment was a split-plot factorial design based on a randomized complete block design with three replications. The main plot factor was the planting season (spring and summer seasons). Sub-plot factors were the factorial combination of coating type and urea-N rate. The coating factor included uncoated urea (UCU, control), rice bran-coated urea (RBCU), gypsum-coated urea (GCU), and cement-coated urea (CCU). The urea fertilizers were 0, 60, 80, or 120 kg urea ha⁻¹. At the flowering stage, the catalase (CAT) and peroxidase (POD) activity, total soluble phenol content, total soluble protein content, and malondialdehyde (MDA) concentration were measured on the youngest fully expanded leaves. Grain yield was measured at physiological maturity from a 2-m² area in the central two rows of each plot.<br /><strong>Results:</strong> Across years, RBCU at 80 kg urea ha^-¹ provided the most consistent balance between antioxidant protection and yield performance under summer heat stress. Under summer heat, RBCU significantly enhanced the enzymatic antioxidant shield, increasing CAT and POD activity, compared to the stressed uncoated urea control. It also elevated non-enzymatic defense by increasing total soluble phenols under summer heat compared with uncoated urea. This coordinated upregulation was associated with a significant containment of oxidative damage. While heat stress increased malondialdehyde content, RBCU at 80 kg urea ha^-¹ resulted in lower MDA compared with the excessive 120 kg urea ha^-¹ treatment. Concurrently, RBCU improved the total soluble protein content under stress. This physiological resilience was associated with improved agronomic performance; RBCU at 80 kg urea ha^-¹ increased grain yield compared with the unfertilized control and outperformed uncoated urea under summer conditions.<br /><strong>Conclusion</strong>: RBCU-mediated nitrogen synchronization improved redox balance and limited lipid peroxidation under field heat stress, supporting both physiological stability and yield maintenance in proso millet. https://breeding.tabrizu.ac.ir/article_21278_e3168be876481c5fc34a9445554c36e9.pdf