Palladium (Pd) is part of the platinum group elements (PGE) and has been shown to be progressively accumulating in roadside soil as a result of ongoing emissions from automotive catalytic converters. The accumulation of Pd is an issue of concern due to the potential impacts on the terrestrial ecosystems along the roadside, such as home vegetable gardens.
Therefore, our study aimed to assess the localisation of Pd in dwarf pea (Pisum sativum) in different aged leaves and the metal-induced impacts on its growth. Plants were cultivated hydroponically in Pd concentrations ranging from 0.1 to 50 ppm. Plant morphology (plant height, leaf colour and leaf area) and health spectral indices (e.g., Normalized Digital Vegetation Index) were measured on days 10, 17, 24 using MicroScan PlantEye. After 24 days, roots, young leaves, old leaves, florets and pods were harvested separately from each of the plants and analysed for Pd using ICP-MS.
The results showed that Pd has significant impacts on the growth of P. sativum at high concentrations (10, 50 ppm). Excess Pd resulted in reduced biomass, leaf area, root volume and length, earlier flower-to-pod conversion, and increased chlorophyll content. However, a stimulatory effect on roots was observed in Pd treatment at low concentrations (0.1 and 1 ppm). Pd were accumulated in the plant, reaching over 18 ppm in young leaves and 28 ppm in old leaves in 50 ppm Pd treatment. Furthermore, it was shown that older leaves bioconcentrate more Pd than younger leaves.The negative impacts of Pd on plant growth together with evidence of Pd accumulation suggested potential contamination of food plants and the risk of entering the food chain.