Anna Febrero

Detection and Quantification of Unbound Phytochelatin 2 in Plant Extracts of Brassica napus Grown with Different Levels of Mercury

The mercury (Hg) accumulation mechanism was studied in rape (Brassica napus) plants grown under a Hg concentration gradient (0 μm–1,000 μm). Hg mainly accumulated in roots. Therefore, the presence of phytochelatins (PCs) was studied in the roots of the plants. The high stability of the PC-Hg multicomplexes (mPC-nHg) seems to be the main reason for the lack of previous Hg-PC characterization studies. We propose a modification of the method to detect and quantify unbound PC of Hg in plant extracts via high-performance liquid chromatography coupled to electrospray tandem mass spectrometry and inductively coupled plasma mass spectrometry in parallel. We separated the PC from the Hg by adding the chelating agent sodium 2,3-dimercaptopropanesulfonate monohydrate. We only detected the presence of PC after the addition of the chelating agent. Some multicomplexes mPC-nHg could be formed but, due to their large sizes, could not be detected. In this study, only PC2 was observed in plant samples. Hg accumulation was correlated with PC2 concentration (r2 = 0.98).

Physiological responses of Eichhornia crassipes [Mart.] Solms to the combined exposure to excess nutrients and Hg

In the present study the physiological response of water hyacinth (Eichhornia crassipes [Mart.] Solms) to the combined exposure of excess nutrients and Hg was examined. Young water hyacinth plants were exposed to a range of HgCl2 and KNO3 concentrations. After eight weeks, submerged plant tissues reached an Hg concentration of 4 mg g-1. The accumulation of P and S was reduced by the addition of HgCl2, and also the P and K concentrations in emerged and submerged parts decreased. In contrast, the addition of HgCl2 increased Ca and Mg concentrations in submerged parts. Furthermore, the concentration ratios of submerged/emerged parts for Ca, Mg and P were also reduced by the addition of HgCl2. The interaction of HgCl2 and KNO3 was synergistic and decreased Fv/Fm, total chlorophyll content and P and Mn concentrations in emerged parts. In submerged plant parts Ca concentration increased and K content stabilized as a result of the above interaction. However, the total accumulation of Hg per plant was not reduced, thereby confirming the water hyacinth as a promising candidate for the heavy metal phytoremediation of eutrophic waters.