Synergistic effect of arbuscular mycorrhizal fungi, biochar and seaweed extract for improving the copper tolerance in hemp

Contamination of soil with copper (Cu) is widespread because of industrialization, use of copper-based fertilizers and natural weathering of rocks. Copper (Cu) toxicity in agricultural lands is a growing global concern, but not a single study has been conducted till now on its alleviation by the synergistic effect of arbuscular mycorrhizal fungi (AMF), biochar (BC) and seaweed extract (SWE) in hemp. For this purpose, pot trial was conducted to evaluate various treatments i.e., BC addition [with BC and without BC] and soil application of AMF and various levels of SWE (T0 = control, T1 = AMF 10 g per pot, T2 = SWE 1 g L-1; T3 = SWE 3 g L-1; T4 = T1 + T2; T5 = T1 + T3) on the hemp productivity and Cu accumulation grown under artificially spiked Cu stressed soil (300 mg kg- 1). Finding revealed that spiking of Cu significantly modulates the growth, biomass, photosynthetic and Cu accumulation attributes of hemp plant. A linear decrease in the leaves dry weight (45.50 %), stem diameter (21.70 %), total chlorophyll contents (54.33 %) while increase in the enzymatic antioxidants, oxidative stress and Cu accumulation attributes was noticed under Cu stressed soil. The simultaneous application of BC, AMF and SWE resulted in substantial enhancements in growth and biomass traits in comparison to untreated Cuexposed plants. Synergistic approach of all the biostimulants application effectively reduced hydrogen per oxide (H2O2) production (50.83 %), proline accumulation (45.66 %) and generation of malondialdehyde (43.43 %), while increasing osmolytes accumulation i.e., soluble sugars (52.75 %) and soluble protein (87.15 %) in comparison with control. Furthermore, the synergistic effect of all biostimulants minimized the Cu accumulation in the hemp. Specifically, the cumulative impact Cu stress was mitigated by combined approach BC, AMF and SWE treatments, which increased growth, biomass, antioxidant enzyme activity, and osmoprotectants levels by limiting Cu accumulation. The combined novel approach of BC, AMF and SWE holds a practical approach for the alleviation of Cu stress for hemp production. This approach provides a comprehensive solution for successful hemp cultivation in Cu-contaminated soil, and thus, for remediating Cu contaminated soil.