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Abstract

Globally, the risks, environmental and health-wise, posed by soil contamination with heavy metals, particularly lead (Pb) and aluminum (Al), is significant. The use of ornamental plants, in phytoextraction, as a remedy strategy against this contamination is not only aesthetically viable but also a sustainable strategy. Two ornamental species: Bougainvillea spectabilis and Zinnia elegans were evaluated in this study for their potential to extract Pb and Al from contaminated soil. The study also assessed the role of organic fertilizer (5% farmyard manure) in boosting their phytoextraction efficiency. Under controlled greenhouse conditions, plants were subjected to three concentrations (100, 200, and 300 mg kg⁻¹) each of Pb (as Pb(NO₃)₂) and Al (as AlCl₂), with or without organic amendment. Morphological, physiological, and biochemical parameters were measured six weeks post-treatment conditions. The results revealed that both Pb and Al significantly (p≤ 0.05) led to reduction in the plant height, leaf number, leaf area, and biomass in both species. These adverse effects were, however, ameliorated by the use of organic fertilizer as growth parameters were improved by up to 28%. Physiological parameters like, stomatal conductance, transpiration rate, chlorophyll fluorescence (Fv/Fm), and total chlorophyll content, were also affected negatively by the heavy metal soil contamination. These indicators, nevertheless, were also ameliorated with the of organic amendment. The increase in metal accumulation in shoots and roots was proportional with rising external concentrations. Comparatively, the shoots recorded higher accumulation than roots. The translocation factor (TF) was increased by up to 75% in B. spectabilis and 72% in Z. elegans as organic fertilizer further improved metal uptake and translocation. Taken together, these results upholds that organic fertilizer greatly promotes the growth, physiology, and metal-accumulating capability of both B. spectabilis and Z. elegans. Therefore, this investigation lends credence to the adoption of organic-amended ornamental plants as an efficient, sustainable panacea for the phytoextraction of Pb and Al from contaminated soils, while combining remediation with ecological and aesthetic advantage.

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