Study of protein pattern, antioxidant enzymes and accumulation of cadmium in sunflower (Helianthus annuus L.) treated with cadmium and salicylic acid

In order to investigate the interaction effects of cadmium as a heavy metal and salicylic acid as an antioxidant and anti-stress substance on sunflower plants, sunflower seeds were washed with distilled water after disinfection with 1% sodium hypochlorite solution and were planted in pots containing sandy soil in a growth chamber with a temperature of 34 ℃ during the day and 25 ℃ at night, and 16/8 hours of light/dark photoperiod. This research was performed as a factorial completely randomized design with four replications under greenhouse conditions. Sunflower plants were exposed to cadmium chloride treatment (0, 50, 100, 150 and 200 µM) at two-leaf stage on a weekly basis. One week after cadmium treatment, plant leaves were sprayed with salicylic acid (0, 250 and 500 µM). After harvesting the plants, cadmium concentrations in roots and shoots were measured. Then, antioxidant enzymes were assayed. Total protein content of leaf samples was extracted and the pattern of leaf protein changes was investigated by SDS-PAGE electrophoresis. Cadmium concentration in roots and shoots increased with increasing cadmium and salicylic acid treatment. Catalase enzyme activity decreased with increasing cadmium concentration, and salicylic acid had a very small effect on its activity. The activity of superoxide dismutase, ascorbate peroxidase, and glutathione reductase enzymes increased with increasing cadmium concentration while increasing salicylic acid concentration reduced the activity of these enzymes. Leaf protein electrophoresis under cadmium and salicylic acid treatments showed differences in leaf protein intensity compared with control plants. The expression of some proteins was increased or decreased in the treated plants. Therefore, cadmium and salicylic acid treatments made changes in the amount of cadmium uptake, antioxidant enzymes activity, and the pattern of sunflower leaf proteins.