PB UPTAKE AND BIOACCESSIBILITY IN VEGETABLES GROWN ON PB-CONTAMINATED SOILS

Abstract

Lead (Pb) is an environmental pollutant that is toxic to plants and humans. A pot experiment was conducted to evaluate the effect of Pb stress on growth, oxidative status, antioxidant response, Pb uptake, and in vitro gastrointestinal bioaccessibility in root vegetables, including radish (Raphanus sativus) and turnip (Brassica rapa), and leafy vegetables, including spinach (Spinacia oleracea) and lettuce (Lactuca sativa). The vegetables were grown under four Pb treatments (CK, 200, 400, and 600 mg kg-1 soil). Growth and biomass decreased progressively at the highest Pb level (600 mg kg-1). Total chlorophyll also declined with increasing Pb concentration, with reductions of 70%, 65%, 64%, and 60% in spinach, lettuce, turnip, and radish, respectively. At 600 mg kg-1 soil, Pb contents increased most strongly in radish and turnip roots, while spinach and lettuce showed comparatively lower increases. Pb exposure increased MDA contents and altered SOD and CAT activities, indicating oxidative stress. The in vitro gastrointestinal study showed that Pb bioaccessibility varied among vegetable types and digestion phases. In the gastric phase, Pb bioaccessibility ranged from 4.3% to 23% in radish and from 4.1% to 20.3% in lettuce; in the intestinal phase, it ranged from 8% to 33% in radish and from 7.8% to 25.6% in lettuce. For spinach and turnip, gastric bioaccessibility ranged from 3.4% to 20.4% and 3.12% to 17.6%, respectively, while intestinal bioaccessibility ranged from 7.6% to 20.4% and 6.5% to 19.7%, respectively. These results indicate that Pb uptake and gastrointestinal bioaccessibility differ among vegetable species and edible parts. Because no Caco-2 cell or in vivo absorption assay was conducted, the study is interpreted in terms of bioaccessibility rather than bioavailability.