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Abstract
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Among the heavy metals, cadmium (Cd) is regarded as one of the most toxic metals. This study aimed to conduct a com- prehensive evaluation and comparison of the toxic effects of Cd of soil and air on the important biological properties of D. stramonium for the first time. Four levels of cadmium chloride (0, 75, 150 and 225 ppm) were selected for soil and foliar treatment. Cd accumulation in plant tissues, growth factors, relative water content of tissue, membrane stability index, photosynthetic pigments content, soluble carbohydrate content, total protein content, antioxidant enzyme activity, genotox- icity and DNA methylation percentage in D. stramonium was studied. The results of experiments showed that Cd uptake increased greatly with enhancing the concentration of the element. The maximal Cd concentration of shoot was 63.27 and 111.61 mg kg-1 DW in the soil and foliar treatment, respectively, when the Cd treatment was 225 ppm. The decrease in growth factors, relative water content, membrane stability index, photosynthetic pigments content and soluble carbohydrate content and the increase in total protein content and antioxidant enzyme activity were observed. The highest and the lowest changes of DNA were observed in the soil treatment group of 225 ppm (GTS = 78.20) and 75 ppm (GTS = 91.02), respec- tively. Changes in DNA band patterns reflected various types of DNA damages and mutations. In this way, it can be concluded that Cd has genotoxic effects. DNA methylation pattern showed that Cd increased the percentage of DNA methylation in the treated groups. It seems that the increased methylation could raise the tolerance to Cd.
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