Effect of mixed cadmium, copper, nickel and zinc on seed germination and seedling growth of safflower

Elevated levels of heavy metals in contaminated soils are widely spread and concerns have been raised over the potential risks to humans, animals and agricultural crops. This study was conducted to evaluate the effect of mixed cadmium, copper, nickel and zinc on seed germination and seedling growth of safflower under controlled light and temperature conditions. Treatments were included 0 (control), 60, 120, and 180 mg kg(-1) which were made by equal amounts of cadmium (1/4), copper (1/4), nickel (1/4), and zinc (1/4). The heavy metal mixture treatment showed toxic effects on seed germination and seedling growth of safflower. Increasing the concentration of heavy metal mixture to 180 mg kg(-1) showed a significant decrease in seed germination as compared to control treatment (p<0.01). Heavy metal mixture concentration of 60 mg kg(-1) reduced shoot fresh and dry weight (p<0.01). Root fresh and dry weight was diversely affected by the heavy metal treatment. However, the heavy metal mixture concentration of 180 mg kg(-1) produced the lowest amount of both root fresh and dry weight. A negative response of root and shoot length of safflower to heavy metal mixture application relative to control treatment was observed at 120 mg kg(-1) (p<0.01). The study suggests that cultivation of safflower in metal polluted soils should be avoided or appropriate control measures be adopted to maintain the heavy metal content of the soil below the damage threshold level. The heavy metal mixture treatment of 60 mg kg(-1) exhibited the lowest percentage of tolerance in germination and seedling growth characteristics of safflower as compared to control.