Integrated nutrient and plant growth regulator management improves cadmium phytoextraction in Ricinus communis

Rapid industrialization and urbanization have intensified cadmium (Cd) contamination in terrestrial ecosystems. The development of sustainable and low-impact remediation approaches are therefore essential. Phytoremediation using plant species displaying high Cd tolerance offers a promising solution for Cd-extraction from contaminated soils. Current study investigated the effects of plant growth regulators (PGRs; gibberellic acid and indole-3-acetic acid) and macronutrient fertilization on growth performance, biochemical traits and Cd phytoextraction efficiency of Ricinus communis (R. communis). A controlled pot experiment was conducted using a completely randomized design with five replicates and integrating different combinations of PGRs and macronutrients treatments under Cd stress conditions. The plants, after harvest, were separated into roots, stems and leaves for comprehensive evaluation of growth and biochemical parameters. The combined treatment (NPK + GA₃ + IAA) produced the greatest increases in biomass accumulation, achieving fresh and dry weights of 3.83 and 1.53 g pot⁻¹ in roots, 1.53 and 0.61 g pot⁻¹ in shoots, 1.63 and 0.98 g pot⁻¹ in leaves, and 5.81 and 2.93 g pot⁻¹ for total plant biomass, respectively. A substantial improvement of 2.48 and 1.85 fold in the contents of Chlorophyll-a and chlorophyll-b, respectively, was recorded when compared to the control (C1) plants. Proline and total phenolics increased substantially in both roots and leaves, indicating an improved osmotic adjustment and stress-tolerance. Antioxidant enzyme activities (catalase, superoxide dismutase, and peroxidase) were significantly enhanced under the combined treatment. Moreover, Cd phytoextraction efficiency improved considerably exhibiting a maximum bioconcentration factor of 2.54. These findings demonstrate a significant enhancement in Cd-tolerance level, biomass productivity, antioxidant-mediated defense and phytoextraction potential of R. communis, henceforth, highlighting its promise for sustainable remediation of the Cd-contaminated soils.