Effects of interactions between cadmium and zinc on phytochelatin and glutathione production in wheat (Triticum aestivum L.)

It has been proposed that phytochelatins (PCs) act as a biomarker for the evaluation of metal toxicity. Little attention has been paid to the effects on metal combinations and glutathione (GSH), the most abundant cellular thiol. In the present study the effects of interactions between cadmium (Cd) and zinc (Zn) on PC and GSH production were examined in wheat tissue over 14 days' exposure. The results showed that the presence of Zn alleviated Cd toxicity, accompanied by a reduction of Cd uptake. Cd and Zn exposure increased PC-SH levels in concentration-, tissue- and time-dependent manners. Of the two metals, Cd was more effective than Zn in PC-SH production. Interactions of Cd and Zn with respect to PC-SH production may be synergistic or inhibitory, strongly depending on duration of exposure and concentration of the metal combinations. Cd also stimulated GSH production in concentration-, tissue- and time-dependent manners, whereas Zn had no significant effects on GSH levels. Compared to the presence of Cd alone, the presence of Zn reduced GSH levels in a tissue-dependent manner over the growth period. The results of the study suggest that metal interactions should be highly considered in the application of PCs and GSH as potential biomarkers for the evaluation of metal toxicity, as most metal-polluted natural environments are contaminated with more than one metal.