Synergistic effects of biochar and abscisic acid improved root morphology, antioxidant defense system and decreased availability and bioaccumulation of cadmium in Triticum aestivum (L.) under cadmium stress

Biochar (BC) and abscisic acid (ABA) may deliver positive physiological effects on heavy metal-stressed plants but their interactive role for regulating cadmium (Cd) availability in agricultural soils is unclear. This study revealed that the Cd-induced oxidative stress significantly reduced the growth of wheat, physiology and antioxidant responses. Interestingly, the co-application of BC (2.5 %) and ABA (20 μmol L⁻¹) restored the growth of wheat plants by minimizing Cd accumulation and translocation than their single use. The co-application of these amendments significantly increased the tissues biomass by 36 %, total root volume (29 %), root surface area (44 %), foliar Chl-a and Chl-b by 59 % and 55 % at 10 mg kg⁻¹ Cd than control. Elevated Cd levels increased the proline, MDA and H₂O₂ contents, while BC and ABA applications ameliorated the Cd-induced oxidative injury by boosting the enzymatic activities of catalase by 46 %, ascorbate-peroxidase by 46 % and peroxidase by 37 % at 10 mg kg⁻¹ Cd. The Cd treatment also increased Cd levels in soil, root and shoot tissues of wheat plants. The co-application BC and ABA reduced DTPA-extractable soil Cd by about 3-fold at 5 mg kg⁻¹ and by about 1.8-fold at 10 mg kg⁻¹, as compared to respective controls. The combined BC + ABA treatment reduced Cd biological accumulation by 35 % and 33 %; and Cd translocation by 21 % and 9 % at 5 and 10 mg kg⁻¹ Cd levels than control. It was concluded that the combined BC+ABA application restored the growth, physiology, antioxidant enzymatic activities and minimized Cd bioaccumulation in wheat tissues.