The effect of N form (NO 3 − versus NH 4 + ) on growth and uptake of Cd and Zn by the hyperaccumulator Thlaspi caerulescens (Ganges ecotype) was investigated in hydroponic and rhizobox experiments. In the hydroponic experiments, NO 3 − or NH 4 + was supplied to plants with the pH of the nutrient solution being unbuffered or buffered at around 6.0. A moderately contaminated soil was used in the rhizobox experiment with or without additions of NO 3 − , NH 4 + or NH 4 + + DCD (dicyanodiamide, a nitrification inhibitor). A higher biomass was obtained when N was supplied as NO 3 − in both experiments, indicating that T. caerulescens prefers NO 3 − over NH 4 + . In the hydroponic experiments, supplying NO 3 − resulted in a doubling of Cd concentration in the shoots compared with the NH 4 + treatment, regardless whether solution pH was buffered or not. The form of N also had a noticeable effect on root Zn concentrations. In the rhizosphere box experiment, rhizosphere pH was markedly influenced by the N treatment. The acidification in the NH 4 + and NH 4 + + DCD treatments increased the concentrations of extractable Cd and Zn, both of which showed a considerable depletion in the rhizosphere. However, total uptake of Cd and Zn were highest in the NO 3 − treatment, despite the fact that concentrations of extractable Cd and Zn in the rhizosphere were the lowest in this treatment. The results showed that supplying N as NO 3 − promoted growth and phytoextraction of Cd and Zn by T. caerulescens compared with NH 4 + .

No abstract

No abstract

No abstract