Alteration in chemical form and subcellular distribution of cadmium in maize (Zea mays L.) after NTA-assisted remediation of a spiked calcareous soil

Phytoremediation has been proposed as a cost-effective method for removing potentially toxic elements (PTEs) from the soil. In this regard, biodegradable chelating agents can be used without harming the environment to increase the efficiency of phytoremediation. In the present work, a greenhouse experiment was conducted to investigate the effect of nitrilotriacetic acid (NTA; 0, 15, and 30 mmol L −1 per pot) on the uptake, chemical forms, and subcellular distribution of Cd in maize ( Zea mays L.) grown in Cd-spiked soils (0, 25, and 50 mg Cd kg −1 soil) under leaching conditions. NTA application decreased biomass production (18–33%) yet enhanced Cd concentrations in shoots and roots of maize by more than 50%. Subcellular fractionation of NTA-applied Cd-containing leaves indicated that 41–53% of the Cd was localized in cell walls ( F CW ), 33–39% in soluble fraction ( F S ), and 13–19% in cellular organelles ( F O ). Moreover, NTA enhanced inorganic ( F E ), water-soluble ( F W ), and pectates and proteins-integrated Cd ( F NaCl ) forms, but reduced the insoluble forms ( F HAc and F HCl ). The increase of F NaCl may possibly help the plant to adapt to Cd stress. Also, NTA decreased soil DTPA-extractable Cd significantly, due to the increase in Cd leached and Cd absorbed by plants. The use of NTA can significantly increase the phytoremediation potential of maize, but it may also increase Cd toxicity in plants exposed to high amounts of Cd. Therefore, it is important to determine the optimal amount of chelator for enhancing phytoremediation.