Abstract
Nitrogen fertilization could improve the efficiency of Cd phytoextraction in contaminated soil and thus shorten the remediation time. However, limited information is available on the effect of N form on Cd phytoextraction and associated mechanisms in plants. This study examined the effect of N form on Cd accumulation, translocation, and speciation in Carpobrotus rossii and Solanum nigrum Plants were grown in nutrient solution with 5-15 μM Cd in the presence of 1000 µM NH4 (+) or NO3 (-) Plant growth and Cd uptake were measured, and Cd speciation was analyzed using synchrotron-based X-ray absorption spectroscopy. Shoot Cd accumulation was 30% greater with NH4 (+) than NO3 (-) supply. Carpobrotus rossii accumulated three times more Cd than S. nigrum. However, Cd speciation in the plants was not influenced by N form, but it did vary with species and tissues. In C. rossii, up to 91% of Cd was bound to S-containing ligands in all tissues except the xylem sap where 87-95% were Cd-OH complexes. Furthermore, the proportion of Cd-S in shoots was substantially lower in S. nigrum (44-69%) than in C. rossii (60-91%). It is concluded that the application of NH4 (+) (instead of NO3 (-)) increased shoot Cd accumulation by increasing uptake and translocation, rather than changing Cd speciation, and is potentially an effective approach for increasing Cd phytoextraction.
Highlights
Widespread in the environment, cadmium (Cd) is a non-essential element with no known physiological functions
This study examined the effect of N form on Cd accumulation, translocation, and speciation in Carpobrotus rossii and Solanum nigrum
The present study aimed to examine the effect of N form on Cd uptake and accumulation in two Australian native plant species, Carpobrotus rossii and Solanum nigrum, with both species having shown potential for Cd phytoextraction (Wei et al, 2013; Zhang et al, 2014)
Summary
Widespread in the environment, cadmium (Cd) is a non-essential element with no known physiological functions. It enters soil from a variety of sources including application of metal-containing sewage sludge, phosphate fertilizers, waste from incinerators, and other industrial wastes (Nicholson et al, 1994). Cadmium presents a risk because it accumulates readily in plants to levels that are harmful in animal and human diets. Phytoextraction reduces metal concentrations in contaminated soils through the accumulation of these metals in the above-ground biomass of plants. For this purpose, hyperaccumulators are plants that can accumulate metals to levels at
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