Biosynthesized hematite nanoparticles mitigate drought stress by regulating nitrogen metabolism and biological nitrogen fixation in Trigonella foenum-graecum

Abstract

The widespread and increasing use of biosynthetic hematite nanoparticles (HNPs) has led to their application in agriculture. Drought poses a significant threat to crop development and production in agricultural regions around the world. Two varieties of Trigonella foenum-graecum, Afg 1 (drought tolerant) and Afg 3 (drought sensitive) were treated with 20 and 50 mgL−1 HNPs concentrations tested under 5 and 10 days drought stress with control. Both Afg 1 and Afg 3 varieties responded most efficiently at a concentration of 50 mgL−1 HNPs in mitigating drought stress. HNPs reduced proline, nitrate, and ammonia concentrations by 22.4%, 25%, and 37% respectively. They are involved in nitrogen regulation and accumulate in dose-dependent manner during drought stress, causing toxicity. HNPs were found to be important in positively regulating the activity of nitrogen metabolizing enzymes (p ≤ 0.05). Nitrate reductase, glutamine synthetase, and glutamate synthase are increased by 41%, 80%, and 63% respectively. This study suggests that HNPs enhance the ability of Trigonella foenum-graecum to maintain high nitrogen metabolism and biological nitrogen fixation. nifH gene expression increased by 21.7% under drought stress by alleviating the Fe micronutrient deficiency in plants caused by dry soil alkalinity.