Analysis of phytochelatins and Hg-phytochelatin complexes in Hordeum vulgare plants stressed with Hg and Cd: HPLC study with amperometric detection

Abstract

Several parameters related to metal stress have been studied in Hordeum vulgare plants treated with Cd and Hg at different doses to provide new insights concerning toxicity and resistance mechanisms produced by these metals. To the best of our knowledge, for the first time the simultaneous stress by Hg and Cd has been investigated. Growth inhibition has been evaluated showing clear symptoms of phytotoxicity in metal stressed plants. Hg and Cd content evidenced the ability of this plant species to uptake and accumulate toxic metals in its tissues. Moreover, when both metals were present, regardless of their concentration, a lower uptake of Hg was observed leading us to conclude that Hordeum vulgare plants have less affinity for Hg when there is cadmium competing in the media. To explore a way of following toxic metal stress response in plants, HPLC with amperometric detection has been used to study different thiols: gluthatione (GSH), its fragments and several phytochelatins (PC2–5). The accumulation mechanism of these metals could be explained by the formation of PCs and their Hg complexes, which play an important role in metal detoxification. As expected, Cd was shown to be a greater PC inductor than Hg. PC2 might be used as a marker of metal stress in plants because it increases according to the concentration of metals supplied to the plant.