Evaluation of antioxidant defense responses in Artemisia annua L. shoot cultures under silver nitrate stress

In plants, several protective systems cooperate to overcome stressful conditions such as the pollution of the medium to heavy metals. In this research, the influence of different concentrations of silver nitrate on growth index, chlorophyll content, H2O2 content, lipid peroxidation, proline content, and the activity of antioxidant enzymes in shoot culture of Artemisia annua L. were investigated. In order to show the effects of the silver as heavy metal, on the aforementioned indices, the experiment was carried out in a completely randomized design with 3 replications. The different concentrations of silver nitrate (0, 0.001, 0.01, 0.1, 1, and 2 mM) were added to liquid MS medium including Artemisia shoot. The results showed that the ratio "fresh weight/dry weight" of the treated samples in 0.1 mM concentration of silver nitrate was increased relative to the control. Chlorophyll a and b contents were increased in 0.001 mM concentration and chlorophyll a was decreased in 0.1 mM concentration in comparison to the control. Among the measured antioxidant enzymes activity, only catalase was increased in all concentrations. Silver nitrate elicitor caused proline, H2O2, and lipid peroxidation to be increased in all concentrations. This study showed that the silver led to the accumulation of H2O2 as a signal and induced the antioxidant defense in shoots.