EDTA reduces the physiological damage of lead on cardoon plants grown hydroponically

Abstract
Cardoon seedlings (Cynara cardunculus L.) were grown hydroponically in nutrient solution and exposed to lead (Pb ²⁺: ImM) in the presence of a range of different EDTA concentrations (EDTANa ₂: 0, 0.5, 1 or 2mM). Analyses were performed to establish whether the coordination of Pb ²⁺ transport by EDTA enhances the mobility of this metal within the plant and to determine the toxic effects of these treatments during a phytoextraction process. Net photosynthesis, transpiration rate and stomatal conductance decreased dramatically in plants treated with Pb ²⁺ or Pb-EDTA at doses below 1 mM. ln these treatments, most of the Pb ²⁺ accumulated in the roots, alld only a very low amount of it was translocated to the shoots. Increasing the EDTA doses up to Pb ²⁺ equimolarity, increased the Pb ²⁺ shoot content more than 10-fold without any physiological evidence of toxicity. The treatment with higher doses of EDTA (Pb ²⁺ 1 mM + EDTA 2 mM) did not show toxicity symptoms, but the Pb ²⁺ concentration in the aboveground tissues decreased when compared with the equimolar treatment. The interaction with the absorption of some essential cations such as Ca ²⁺ and phytotoxicity on chelated-assisted phytoextraction is discussed.