Effect of salicylic acid and potassium nitrate pretreatment on enhancing the sunflower tolerance in contaminated soils with cadmium

In the contaminated soils, the poor plant establishment and reduction in  plant biomass will reduce the efficiency of phytoremediation. In this study the effect of sunflower seed pretreatment with salicylic acid (100 mg/L) and potassium nitrate (2%) on its enhancing tolerance under different concentrations of cadmium (0, 50 and 100 mg/kg) were evaluated. Results showed that increasing of cadmium concentration significantly reduced the root dry weight, stem dry weight and leaf dry weight, chlorophyll a, chlorophyll b and increased carotenoids, proline content and electrolyte leakage. Seed priming with salicylic acid and potassium nitrate improved the damage effect of contaminated soil with cadmium on mentioned parameters. Under cadmium stress, potassium nitrate increased stem dry weight, leaf dry weight, chlorophyll a, aboveground cadmium concentration, and translocation factor. However, salicylic acid increased root dry weight, chlorophyll b and root cadmium concentration. Under highest concentration of cadmium, electrolyte leakage and proline content were reduced by salicylic acid (by 18%, 22%, respectively). In general it can be concluded that salicylic acid and potassium nitrate with increasing photosynthesis pigments and proline content and reducing electrolyte leakage increased of sunflower tolerance in contaminated soils with cadmium