Bioindication of heavy metal contamination in vegetable gardens

Private vegetable gardens are often contaminated with elevated levels of heavy metals (HM). Bioindication, using the visible symptoms developing in leaves, can provide simple, cost-effective and reliable detection of soil pollution. In this experiment five species of vegetables from different families were exposed to soil contaminated with HM dust given as copper / zinc / cadmium/ lead = 640 /3000 /10 /90 mgkg-1 vs. uncontaminated control soil (copper / zinc / cadmium/ lead=28 / 97 /0.1 /37 mgkg-1) to study HM uptake and stress reactions and validate markers of HM intoxi cation within each species. Each vegetable reacted specifically to the HM exposure. Characteristic leaf symptoms were found in Raphanus and Phaseolus associated with a reduced shoot:root biomass ratio, higher content of HM and cytochemical localisation of zinc matching reactions for stress, defence and detoxification. They were primarily attributed to the direct effects of zinc and the mixed indirect effects of all HM. Thus, two out of the five species showed a usable and promising bioindication potential to monitor HM pollution in vegetable gardens. In urbanized environments, bioindication using vegetables showing leaf symptoms can help to raise public awareness regarding food safety.