Potential role of nitrogen supplementation in alleviating flooding stress

Flooding is one of the most damaging abiotic stresses, affecting seventeen million square kilometers of land surface per year, and it is expected to increase in severity in many parts of the world with climate change. Therefore, understanding the mechanisms by which plants cope with flooding stress is important for the development of new flood-tolerant cultivars. The aim of this study was to investigate the effects of different nitrogen doses [no-nitrogen(N0), 100 kg ha-1 (N10), and 200 kg ha-1 (N20)], on the physiological responses of plants under flooding stress. In this context, spinach plants were subjected to flooding stress, and several physiological, biochemical, and nutritional parameters were investigated. The results showed that flooding stress caused a decrease in aboveground fresh and dry weight of spinach, while chlorophyll a (Cl a), b (Cl b), and total chlorophyll (TCl), as well as carotenoid, protein, and proline contents, increased. In addition, the uptake of the macronutrients N, P, K, and Mg increased during flooding stress. N application under flooding stress alleviated its negative effects and suppressed the induction of H2O2 through increased proline biosynthesis. Similarly, Cl a, Cl b, and TCl levels minimized the negative effects of flooding stress. In conclusion, different N doses improved spinach plant parameters and alleviated the effects of flooding stress, with N10 application in particular N10 improved biomass by 22% under flooding producing significant results in suppressing the detrimental effects of stress.