Effects of Irrigation Water Cadmium Concentration on Yield and Growth Traits of Green Pepper (Capsicum frutescens)

Cadmium is a highly toxic heavy metal and one of the most important environmental pollutants. Cadmium has a particular interest among the heavy elements due to the high mobility, solubility, and toxicity for human, plants, and other organisms. In order to study cadmium toxic effect on green pepper, a completely randomized design was performed with three levels of cadmium (0, 0.25, and 0.5 mM as cadmium chloride) in three replications under greenhouse conditions. The result showed that cadmium had a negative effect on some morphological traits of green pepper. In this regard, concentration of 0.5mM of cadmium caused significant decrease(p<0.05) in root volume, root length, leaf number, fresh weight and dry weight of shoot and root by, respectively, 45.8%, 12.2%, 18.5%, 38%, 15.3%, and 20.7 percent compared to the control. Also, results showed that increase in the levels of cadmium lowered the content of photosynthesis pigments: at the concentration of 0.5mM, cadmium caused a significant reduction(p<0.05) in chlorophyll a, b and total chlorophyll content at the rate of, respectively, 26.5%, 34.7%, and 18.2 percent relative to the control. Besides, analysis of variance showed significant reduction in the relative water content of plant tissue as affected by cadmium toxicity: this index decreased 14.5 percent compared to the control treatment. But, there was no significant difference between the two levels of cadmium treatment (p<0.05). According to the results of the present study, cadmium caused reduction of growth, damage to the plant, and had negative effect on physiological processes of green pepper. In general, the toxicity of this element varies in different plant species and cultivars, therefore, more studies will be useful on different crop varieties.