Plant growth-promoting bacteria have fundamental role in enhancing natural bioactive compounds and proved to increase the plant growth and mineral availability in soil. These phytochemicals, like phenolic and essential oils, illustrated wide range of biological properties. This study was designed to evaluate the effect of Azotobacter chroococcum (A. chroococcum) alone or in combination with slight (irrigation at 80% filed capacity) or moderate (irrigation at 60% filed capacity) drought stresses on the yield, phytochemicals, antioxidant, and the toxicity of Trachyspermum ammi (T. ammi) seeds essential oil. Overall, the application of A. chroococcum as plant growth-promoting agent together with slight drought stress significantly (p < 0.05) resulted in higher essential oil yield, total phenolic, total flavonoid, and higher antioxidant activity. The gene expression analysis in the developing seeds confirmed the up-regulation in the expression of antioxidant-related gene (SOD) and thymol synthesis gene (TSG) upon A. chroococcum bacteria treatment in combination with slight drought stress. The toxicity study showed no prominent signs of toxicity in mice upon oral administration of essential oil up to 100 mg/kg body weight for 28 days. The slight drought stress (irrigation at 80% filed capacity) together with treatment of T. ammi plant with A. chroococcum bacteria as plant growth-promoting agent could be promising approach in improving the yield and medicinal value of the T. ammi seeds essential oil.

中文翻译：

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增强 Trachyspermum ammi 种子精油的生物合成和生物活性以应对干旱和深色固氮菌刺激

植物生长促进细菌在增强天然生物活性化合物方面具有重要作用，并被证明可以增加植物生长和土壤中矿物质的有效性。这些植物化学物质，如酚类和精油，展示了广泛的生物学特性。本研究旨在评估Azotobacter chroococcum (A. chroococcum) 单独或与轻度（以 80% 耕地容量灌溉）或中度（以 60% 耕地容量灌溉）干旱胁迫对产量、植物化学物质、抗氧化剂、以及 Trachyspermum ammi (T. ammi) 种子精油的毒性。总体而言，A. chroococcum 作为植物生长促进剂的应用以及轻微的干旱胁迫显着（p < 0.05）导致更高的精油产量、总酚、总黄酮和更高的抗氧化活性。发育种子中的基因表达分析证实了在 A. chroococcum 细菌处理和轻微干旱胁迫下抗氧化相关基因 (SOD) 和百里酚合成基因 (TSG) 的表达上调。毒性研究显示，在小鼠中口服高达 100 mg/kg 体重的精油 28 天后，没有明显的毒性迹象。轻微干旱胁迫（以 80% 的田间容量灌溉）以及用 A. chroococcum 细菌作为植物生长促进剂处理 T. ammi 植物可能是提高 T. ammi 种子精油产量和药用价值的有希望的方法. 与轻微干旱胁迫相结合的 chroococcum 细菌处理。毒性研究显示，在小鼠中口服高达 100 mg/kg 体重的精油 28 天后，没有明显的毒性迹象。轻微干旱胁迫（以 80% 的田间容量灌溉）以及用 A. chroococcum 细菌作为植物生长促进剂处理 T. ammi 植物可能是提高 T. ammi 种子精油产量和药用价值的有希望的方法. 与轻微干旱胁迫相结合的 chroococcum 细菌处理。毒性研究显示，在小鼠中口服高达 100 mg/kg 体重的精油 28 天后，没有明显的毒性迹象。轻微干旱胁迫（以 80% 的田间容量灌溉）以及用 A. chroococcum 细菌作为植物生长促进剂处理 T. ammi 植物可能是提高 T. ammi 种子精油产量和药用价值的有希望的方法.