N- or/and P-deprived Coccomyxa chodatii SAG 216–2 extracts instigated mercury tolerance of germinated wheat seedlings

Purpose This research studies the alleviation potential of N- or/and P- deprived Coccomyxa chodatii SAG 216–2 extracts as biostimulants on mercury stress (10 and 30 mg L −1 ) of wheat seedlings. Materials The study includes the interactive effect of mercury and biostimulants on growth, reactive nitrogen and oxygen species, membrane stability, and antioxidant activity in wheat seedlings. Results The imposed toxic effects of Hg-stress on the studied parameters were to a great extent less noticeable under different algal extracts, and the magnitude of augmentation was P-deprived extract > P-&N-deprived extract > N-deprived extract > Normal algal extract. Higher Hg-tolerance modulated by algal extracts, especially P-deprived extract, was associated with high antioxidant capacity and ferric reducing power. These activities could instigate the antioxidant system (enzymatic and non-enzymatic) under Hg-stress. Furthermore, the algal extracts broadly alleviated wheat chelating mechanism deterioration by Hg-stress via enhancing phytochelatins, reduced glutathione, and metallothioneins. Thus, the applied algal extracts retarded Hg accumulation in wheat tissues exposed to Hg stress. In addition, the nitrosative stress induced by Hg-stress in terms of high nitric oxide content was minimized by various algal extracts. All these regulations by algal extracts are reflected in high membrane stability as denoted by the reduction of lipid peroxidation, lipoxygenase, and methylglyoxal as a sign of reducing oxidative damage and reactive oxygen species (ROS). Conclusion Thus, we recommended using the macronutrient-deprived algal extracts of Coccomyxa chodatii SAG 216–2 as potential biostimulants of wheat growth under Hg-stress and may be under other stresses.