Growth and Some Physiological Activities of Pepper (Capsicum annuum L.) in Response to Cadmium Stress and Mycorrhizal Symbiosis

A greenhouse experiment was conducted to investigate the effects of mycorrhial fungus (Glomus mosseae) on cadmium (Cd) toxicity in pepper (Capsicum annuum L. cv. Zhongjiao 105) plants. Half of plants were inoculated with arbuscular mycorrhizal fungi (AMF). Cd was supplied in the form of cadmium chloride at 0.0, 0.1 and 0.5 mM through irrigation water in the soil. Mycorrhizal colonization was higher in the control than in cadmium-treated soil. Dry weights of root and shoot of mycorrhizal (M) plants were higher than non mycorrhizal (NM) ones in both control and cadmium treatments. Measurements of Cd concentration indicated that M plants immobilized more Cd in the root and partitioned less Cd to the shoots. Cd decreased the leaf chlorophyll content, total sugar and total protein contents, and the concentrations of phosphorous and magnesium. M plants had greater contents of chlorophyll, total sugar, total protein and P and Mg concentrations than NM plants. Moreover, increasing the Cd concentration caused an increase in malondialdehyde (MDA) content in leaves of pepper plants; however, M plants showed a lower MDA content than NM plants. Cd decreased the activity of superoxide dismutase (SOD) in leaves of NM and M plants, on the other hand, it increased the activity of peroxidase (POD) and ascorbate peroxidase (APX) in leaves of NM and M plants. APX was stimulated more than POD in M plants versus NM plants, suggesting that APX is a major player in H2O2-scavenging in M plants. The study suggests that mycorrhization with G. mosseae can be a suitable way to induce Cd-stress resistance in pepper plants.