MEDICAGO sativa-mediated green synthesis of Zinc nano-complex: Impacts on the phytochemical properties of Hyssopus officinalis under Alkaline stress

• Zinc nano-complex (Zn NC) improved the antioxidant enzymes activities of hyssop. • Application of Zn NC increased bioactive compounds under bicarbonate stress (BCS). • Zn NC altered the antioxidant phenolic compounds in the leaves of hyssop. • Zn NC improved the content of macro and micro elements in hyssop plant under BCS. The purpose of this study was to investigate the interaction between sodium bicarbonate stress (SBCS) (0, 10, 20, and 40 mM) and zinc nanocomplex (Zn NC) (0, 1, 2, and 4 mM) on the growth and bioactive compounds of Hyssopus officinalis L. plants at the growth stage. The application of Zn NC increased essential oil (EO) production and the biosynthesis of phenolic compounds (PCs) and flavonoids in the plant. The accumulation of these compounds amplified the plant's antioxidant capacity compared to control. Treatment with Zn NC increased these compounds significantly more than alkalinity. 2 mM and 4 mM Zn NCs increased average APX activity substantially by 37 % and 55 %, respectively. The oxidative damage and depletion of mineral nutrients in the leaves were caused by SBCS. However, Zn NC-treated plants significantly increased nitrogen, phosphorus, potassium, zinc, and iron concentrations in the bicarbonate-stressed plants. A 44 % increase in proline content with 20 mM SBCS and 4 mM Zn NCs compared to control was revealed. In alkaline soils, Zn NC can be a beneficial and environmentally acceptable zinc supply that increases plant growth and bioactive compound production. Totally, applying 2 and 4 mM Zn NC treatment can counteract the negative effects of SBCS on plant growth and nutrient uptake.