Biochar and vermicompost modulated Pb toxicity in summer savory (Satureja Hortensis L.) plants through inducing physiological and biochemical changes

The primary environmental factor affecting the biochemical attributes of plants is soil pollution by heavy metals. The detrimental effects of heavy metals on plants can be lessened by soil amendments. The goal of the current research was to determine the potential of biochar (BC) and vermicompost (VC) as soil amendments in reducing Pb toxicity in summer savory (Satureja Hortensis L.) though physiological and biochemical modifications. Therefore, the pot experiment was conducted with Pb toxicity (control (non-Pb), 300, and 600 mg kg soil−1) and soil amendments (control, 2 % BC, 10 % VC, and 1 % BC + 5 % VC) based on a completely randomized design. The results showed that Pb toxicity at 600 mg kg soil−1 led to significant decreases in shoot weight (41 %), root weight (25 %), leaf relative water content (20 %), and chlorophyll content (39 %) compared to the control. However, it resulted in increases in malondialdehyde (61 %) and electrolyte leakage (49 %) when BC and VC were not applied. The results showed that Pb toxicity at 600 mg kg soil−1 led to decreases in shoot weight (41 %), root weight (25 %), leaf relative water content (20 %), and chlorophyll content (39 %), but increases in malondialdehyde (61 %), and electrolyte leakage (49 %) compared to the control in the treatments without BC and VC application. However, BC and VC, particularly their combination were more effective in improving plant growth. The interaction of Pb at 300 mg kg−1 and combined BC and VC resulted in higher total phenolic content, total flavonoid content, essential oil (EO) content, and EO yield with 29, 62, and 39, and 35 % raises compared with the control. Agglomerative hierarchical clustering revealed that Pb at 300 and 600 mg kg soil−1 differed from the control, and that combined VC and BC significantly varied from their individual values. Combining BC and VC is more effective than using them separately in alleviating Pb toxicity, as it enhances plant growth and secondary metabolite production. The results have the potential to benefit the improvement of summer savory resistance in Pb-polluted soils.