Biostimulant-driven enhancement of bioactive compounds in salt-stressed sweet basil (Ocimum basilicum L.)

Basil (Ocimum basilicum L.) is a medicinal and aromatic plant renowned for its bioactive compounds, including phenolics, flavonoids, and essential oils. This study aimed to assess the effects of NaCl-induced salt stress on basil and explore comprehensively for the first time the potential mitigating impacts of various biostimulants. A controlled pot experiment was conducted with NaCl concentrations of 0, 50, and 100 mmol, alongside treatments of Bacillus megaterium (BM), Frateuria aurantia (FA), ascorbic acid (AA), and gibberellic acid (GA). The results showed that BM at 50 mmol NaCl significantly enhanced total antioxidant activity (150.40 mg TE g⁻¹) and total phenolic content (242.17 mg GA 100 g⁻¹). GA at non-saline conditions resulted in the highest carotenoid content (3.42 µg g⁻¹ FW), while BM under non-saline conditions achieved the highest flavonoid content (93.33 mg QE 100 g⁻¹). BM and AA treatments significantly increased salicylic and rosmarinic acids, underscoring the biostimulants' role in enhancing basil's biochemical resilience. Furthermore, biostimulants positively influenced morphological parameters such as plant height, root length, herbal weight, and root weight, with GA and BM treatments exhibiting superior performances under varying salt conditions. The correlation analysis indicated complex interactions among the bioactive compounds, providing insights into their potential roles in basil's biochemical response to saline conditions. These findings underscored the potential of biostimulants to mitigate the adverse effects of salt stress, thereby enhancing basil's resilience and productivity in saline environments.