Lead and nickel effect on some physiological and biochemical characteristics of Anethum graveolens L.

Soil contamination with heavy metals is one of the most important environmental problems in many parts of the world. Nickel (Ni) and lead (Pb) are heavy metals that are major contributors to environmental pollution. Since dill (Anethum graveolens L.) is cultivated as a leafy vegetable in various places, even in heavy metal-contaminated areas, this study was conducted to investigate the effects of lead and nickel on the activity of dill antioxidant enzymes and antioxidant compounds. In this study, dill seeds were planted into pots containing coco peat and perlite and treated with lead nitrate (0, 500 and 1000 μM) and nickel nitrate concentrations (0, 100 and 200 μM) in three replications. After the treatments, the length, fresh weight and dry weight of root and shoot, photosynthetic pigments content, the amount of phenolic compounds, flavonoids, anthocyanins, catalase (CAT), guaiacol peroxidase (GPX), ascorbate peroxidase (APX), superoxide dismutase (SOD) activity and the concentration of Pb and Ni in the shoot and root were evaluated. Use together of lead with nickel on the plant showed that plant length, Chlorophyll a, chlorophyll b, and total chlorophyll decreased respectively to 1.32, 1.02, and 2.03 compared to the control with values of 6.26, 4.54, and 10.32 mg / g under lead and nickel treatments. The anthocyanins, total phenols and flavonoid contents were respectively 4.7, 0.69 and 0.51 mg/g which increased by 23.5, 8.6 and 6.37 compared to the control. CAT, APX and SOD activities increased. Whereas, carotenoid content, fresh and dry weight of roots and shoots, guaiacol peroxidase activity were not affected. Simultaneous use of lead and nickel led to an increase in the amount of lead and nickel in shoot and root. The presence of lead reduces the uptake of nickel by the plant. Accordingly, it seems the plant uses antioxidant compounds such as phenols and some antioxidant enzymes to counter lead and nickel oxidative stress from. On the one hand, the treatment had no effect on fresh and dry weight and also roots and stem length decreased slightly. A number of antioxidant enzymes were activated and the antioxidant compounds increased and the more accumulation of elements in the root, it is possible that even if the plant is not resistant to these stresses, it can grow in the Pb and Ni contaminated soil without serious damage.