Exploring the efficacy of ferrimagnetic chitosan beads and vermichar perlite mix on broccoli ( Brassica oleracea L.) growth under chromium stress

Brassica oleracea L. is one of the most important vegetable crops worldwide but is highly susceptible to yield losses under chromium (Cr) toxicity. This study evaluated the efficacy of ferrimagnetic chitosan beads (FMB) and vermichar-perlite mix biochar (VPM) in alleviating Cr-induced stress. A pot experiment was conducted in a completely randomized design with three replicates per treatment. Results indicated that both FMB and VPM significantly improved soil pH, reduced Cr leaching by 38.5-42.3%, and enhanced phosphorus availability up to two-fold. Under Cr-100 ppm, chlorophyll a and b increased by 8.8- and 3.8-fold, respectively, while antioxidant enzymes (SOD, POD, CAT) decreased by approximately 0.6-fold in amended soils, indicating reduced oxidative stress. Growth attributes such as root length and shoot biomass improved by 67% and 93%, respectively. Yield performance also increased markedly, with the number of pods and seeds increased by 47% and 116% under combined FMB and VPM application compared to Cr-stressed plants. Molecular docking analysis revealed a strong binding affinity of proline to peroxidase (-5.1 kcal mol⁻¹; Ki = 0.18 mM), confirming a mechanistic basis for proline-mediated antioxidant defence. Overall, the combined application of FMB and VPM showed a synergistic potential for improving crop resilience to Cr contamination.