Study of some oxidative parameters induced by drought stress in Nigella sativa under hydroponic culture

Drought stress is one of the main stresses that inhibits the growth of plants due to mainly disturbance of the balance between production of reactive oxygen species and antioxidant defense and thereby causing oxidative stress. Evaluation of medicinal plants tolerance to drought stress in order to plant them in dry region is very important. In this research, oxidative parameters of drought stress induced by different concentration of polyethylene glycol solutions in Nigella plant were investigated. To control experimental conditions including the inhibitory effects of the other factors such as soil nutrition the hydroponic medium was used. In this study, drought stress significantly increased the H2O2 content, lipid peroxidation and lipoxygenase activity which were showed the oxidative stress induced by drought in Nigella plants. Study of the defense mechanisms, through the measurement of the antioxidant enzymes activities indicated that drought stress increased the activity of ascorbate peroxidase, catalase and guaiacol peroxidase. However in this research, we observed that the increment in drought level had no significant effects on catalase and guaiacol peroxidase activity. It seemed that in this investigation the increment of proline might be related to both osmotic and antioxidant characteristic of this compound. Increase of lipid peroxidation and H2O2 content in drought stress showed that the scavenging and quenching of ROS were out of the plant ability and the induction of plant defense mechanism against oxidative damages was not effective.