Journal of Plant Process and Function

Heavy metals are a major environmental problem and have caused serious concerns because of characteristics of carcinogenesis, non-degradability and biological accumulation. Major part of this material is absorbed by plants and leads to inactivation of some enzyme, decreased protein production and disrupting variety of reactions and many cellular functions and growth and development cessation. The aim of this study was to evaluate the treatment effects of mercuric chloride and cadmium chloride on total soluble protein, soluble sugars content, concentration of proline, lysine and methionine amino acids with catalase, peroxidase and polyphenol oxidase activity in Tajan and the Gonbad wheat cultivars. The Seedlings were treated in three leaflets stage with mercuric chloride at concentrations of 5, 10, 15 and 20 µM and cadmium chloride at concentrations of 0.5 and 0.25 mM as well as control. The experiment were conducted as factorial in a completely randomized design with three replications. The results showed that in both Gonbad and Tajan cultivars, mercuric chloride treatment significantly decreased the total soluble sugars content and polyphenol oxidase and increased the amount of protein, proline, lysine and methionine compared to control. In Gonabd, with increasing concentrations of cadmium chloride, total protein, soluble sugar and lysine contents increased but proline and methionine contents reduced. But inTajan cultivar opposite result was obtained. Tajan is therefore more tolerant than Gonbad. Also in Gonabd cultivar, with concentration increasing of mercury, catalase and peroxidase activity were reduced but in Tajan increased activity of these enzymes. With increasing concentration of cadmium activity were reduced compared to control enzymes. Thus, this study showed that treatment with cadmium chloride and mercury chloride at micromolar and millimolar levels is able to stimulate plant defense mechanisms and makes plants more tolerant against stress.