Mitigation of cadmium-induced stress in maize via synergistic application of biochar and gibberellic acid to enhance morpho-physiological and biochemical traits

Abstract Cadmium (Cd), being a heavy metal, tends to accumulate in soils primarily through industrial activities, agricultural practices, and atmospheric deposition. Maize, being a staple crop for many regions, is particularly vulnerable to Cd contamination, leading to compromised growth, reduced yields, and potential health risks for consumers. Biochar (BC), a carbon-rich material derived from the pyrolysis of organic matter has been shown to improve soil structure, nutrient retention and microbial activity. The choice of biochar as an ameliorative agent stems from its well-documented capacity to enhance soil quality and mitigate heavy metal stress. The study aims to contribute to the understanding of the efficacy of biochar in combination with GA 3 , a plant growth regulator known for its role in promoting various physiological processes, in mitigating the adverse effects of Cd stress. The detailed investigation into morpho-physiological attributes and biochemical responses under controlled laboratory conditions provides valuable insights into the potential benefits of these interventions. The experimental design consisted of three replicates in a complete randomized design (CRD), wherein soil, each containing 10 kg was subjected to varying concentrations of cadmium (0, 8 and 16 mg/kg) and biochar (0.75% w/w base). Twelve different treatment combinations were applied, involving the cultivation of 36 maize plants in soil contaminated with Cd (T1: Control (No Cd stress; T2: Mild Cd stress (8 mg Cd/kg soil); T3: Severe Cd stress (16 mg Cd/kg soil); T4: 10 ppm GA 3 (No Cd stress); T5: 10 ppm GA 3 + Mild Cd stress; T6: 10 ppm GA 3 + Severe Cd stress; T7: 0.75% Biochar (No Cd stress); T8: 0.75% Biochar + Mild Cd stress; T9: 0.75% Biochar + Severe Cd stress; T10: 10 ppm GA 3 + 0.75% Biochar (No Cd stress); T11: 10 ppm GA 3 + 0.75% Biochar + Mild Cd stress; T12: 10 ppm GA3 + 0.75% Biochar + Severe Cd stress). The combined application of GA 3 and BC significantly enhanced multiple parameters including germination (27.83%), root length (59.53%), shoot length (20.49%), leaf protein (121.53%), root protein (99.93%), shoot protein (33.65%), leaf phenolics (47.90%), root phenolics (25.82%), shoot phenolics (25.85%), leaf chlorophyll a (57.03%), leaf chlorophyll b (23.19%), total chlorophyll (43.77%), leaf malondialdehyde (125.07%), root malondialdehyde (78.03%) and shoot malondialdehyde (131.16%) across various Cd levels compared to the control group. The synergistic effect of GA 3 and BC manifested in optimal leaf protein and malondialdehyde levels indicating induced tolerance and mitigation of Cd detrimental impact on plant growth. The enriched soils showed resistance to heavy metal toxicity emphasizing the potential of BC and GA 3 as viable strategy for enhancing maize growth. The application of biochar and gibberellic acid emerges as an effective means to mitigate cadmium-induced stress in maize, presenting a promising avenue for sustainable agricultural practices.