Methyl isothiocyanate effect on physiological response and antioxidant enzyme activities in seedlings of Lepidium sativum L. under in vitro condition

One of the major tissue damage following exposure to stress in plants is caused by the oxidative stress. In this study effects of different levels of methyl isothiocyanate on biochemical parameters and antioxidant enzyme activity such as ascorbate peroxidase، catalase and guaiacol peroxidase in seedling Lepidiun sativum L. under in vitro was investigated. The seeds of Lepidium sativum (Garden Cress) were sterilized and then were cultured in MS medium. After 20 days، seedlings were treated with concentrations of 0. 01، 0. 1 and 1 mM methyl isothiocyanate (various levels of stress) under steril condition. After 3 days، results showed chlorophyll a، chlorophyll b، total chlorophyll، carotenoids and protein significantly decreased، while reduced sugar، proline and antioxidant enzymes increased in seedlings which were under oxidative stress. Thus methylisothiocyanate appears to cause oxidative stress and the activation parameters of the plant''s defenses. The maximum and minimum، respectively، at concentrations of 1 mM and 0. 01 mM methyl isothiocyanate observed.