Green-synthesized Graphene Oxide Nanoparticles Alleviate Oxidative Stress and Enhance Cr and Pb Phytostabilization in Crassula Ovata

Heavy metal (HM) stress causes severe physiological damage in plants, limiting their potential for phytoremediation. This study investigated the ability of green-synthesized graphene oxide nanoparticles (GONPs) to mitigate chromium (Cr) and lead (Pb) stress in the succulent Crassula ovata. GONPs were sustainably produced from banana peel waste and characterized using FT-IR, SEM, and EDX. Plants were cultivated for 60 days in contaminated urban soil, with GONPs applied at 100 and 150 mg L⁻¹ via soil and foliar routes. Soil application at 150 mg L⁻¹ most effectively alleviated metal toxicity, significantly increasing plant biomass and promoting substantial recovery of chlorophyll content relative to unstressed controls. This recovery was associated with a marked reduction in oxidative stress, with malondialdehyde (MDA) content decreasing by 22.2% and CaCl₂-extractable Cr and Pb fractions declining by 68.2% and 71.5%, respectively, under soil-applied GONPs. Anatomical analysis showed that GONPs restored tissue compactness and cellular integrity in roots and shoots, which were compromised by metal stress. Furthermore, GONPs amendment enhanced the root sequestration of Cr and Pb while reducing their translocation to shoots, confirming a phytostabilization mechanism. This was supported by a sharp decline (over 70%) in the bioavailable metal fractions in the soil. These findings demonstrate a circular-economy-based phytostabilization strategy, where green-synthesized GONPs simultaneously reduce metal toxicity and enhance plant resilience, offering a sustainable solution for rehabilitating contaminated urban soils using a non-food ornamental plant.