Effects of melatonin pretreatment on germination and growth of Malva parviflora (L.) seedlings under cadmium stress

Cadmium (Cd), as a heavy metal, is one of the most important environmental pollutants. This toxic metal affects the plant physiology due to induction of oxidative stress and reduces germination and seedling growth. Melatonin is an animal hormone that has recently been recognized as a growth regulator and stimulant, as well as an antioxidant in the plants. Some studies have shown that melatonin content increases under various biotic and abiotic stresses to increase the plant tolerance against stress conditions. This study was conducted to survey the effect of the melatonin on germination and growth of Malva parviflora L. seedlings under Cd treatment. The seeds were surface sterilized with 20% sodium hypochlorite and washed three times with distilled water. After pretreatment with different levels of melatonin including 0 (control), 10, 25, 50, 100 and 200 μM, 25 seeds were sown at regular intervals in petri dishes containing 50 μM cadmium nitrate and incubated at 25 ± 2 °C. The experiment was performed in 4 replicates for each treatment for 8 days. Germination parameters were daily evaluated. At the end of the eighth day, the results showed that Cd treatment leads to a reduction in the germination percentage and rate, root and shoot length, fresh weight and seed vigor. All the melatonin pretreatments resulted in a significant increase in mentioned indexes in Cd-exposed seedlings. However, the highest germination percentage and rate and seedling length were observed in pretreated seeds with 10 μM melatonin. Results of this study suggest that seed pretreatment with melatonin, especially at the concentrations less than 25 μM, could reduce the effects of Cd toxicity and improve germination and growth in M. parviflora seedlings.

Keywords:

Melatonin , Cadmium , Seedling establishment , Malva parviflora