The effect of cadmium and mercuric chlorides on some physiological traits in two cultivars of wheat.

One of the important abiotic stresses that negatively affect cereals such as wheat is heavy metals. Soil pollution with heavy metals has become one of the major environmental concerns resulting from the industrial development and use of fertilizers containing heavy metals. One way to counteract the negative effects of heavy metals in plants which produce reactive oxygen species is the activation of antioxidant systems in plant cells. In order to study the physiological traits involved in resistance to these stresses, a factorial experiment was conducted in a completely randomized design with three replications. The first factor was wheat cultivars including Gonbad (tolerant to Fusarium) and Tajan (susceptible to Fusarium). The second factor was spraying heavy metals (mercuric chloride at concentrations of 5, 10, 15, and 20 µM, cadmium chloride at concentrations of 0.25 and 0.5 mM and control) and the third factor was sampling times after treatments (after 8 and 16 hours). The results showed that the total protein and soluble sugar contents increased with cadmium and mercuric chloride treatments. Furthermore, with increasing concentration of mercuric chloride, the catalase, peroxidase, and polyphenol oxidase activities decreased while the activities of these enzymes increased with increasing concentration of cadmium chloride. Thus, this study showed that spraying of cadmium and mercuric chloride at micro- and nano-molar concentrations can stimulate and strengthen plant antioxidant system and make plants more tolerant to heavy metals stresses.