Effects of ZnO nanoparticles on sulforaphane content, biochemical and morphological feathers of Lepidium draba seedlings

Lepidium draba, a perennial plant belonging to the Brassicaceae family, contains high level of the glucosinolate glucoraphanin that  after enzymatic hydrolysis produce sulforaphane. In this study, sulforaphane content, morphological and biochemical properties were analyzed of the treated L. draba seedlings which grown for 7 days in the presence of different concentrations (0 (as control), 25, 50, 100, 250, 500 and 1000 mg/L) of nano zinc oxide (nZnO). Based on the results, seed germination rate was significantly reduced in the presence of concentrations more than 100 mg/L nanoparticle, so that it reduced about 30% in the presence of the highst doses of nZnO. Root and shoot lengths of the treated seedlings were also significantly decreased in compared to the control with the increase nanoparticles concentration in the medium, So that in the presence of the hightst concentration, length of the root and shoot were reduced about 70 and 60 % respectively. Moreover, it is also shown that chlorophyll, carotenoid and flavonoid contents were significantly decreased in treatment with all nanoparticle concentrations compared to the control. In contrast, the results shown that an increase in sulforaphane content in treated seedlings with the concentrations more than 100 mg/L nanoparticle compared to the control. Catalase activity was significantly increased in treated seedlings more than 100 mg/L nZnO concentration compared to the control, so that in the presence of the highst concentration, its activity increased more than 3 factors.  The positive effects of this particle were also seen on soluble protein concentration (in the presence of all nZnO concentrations) and anthocyanin content (up to 100 mg/L nZnO concentrations) in compared to the control sample. Furthermore, the amount of the abzorbed Zn ion in the root and shoot of the treated seedlings increase with the increase nanoparticle concentration in the medium. Overall, based on the increase sulforaphane and anthocyanin contents and activity of catalase, it seems that surface adsorption or accumulation of these particles, induced oxidative stress which resulted in decreasing of seedling growth. So, it is suggested for determining the exact mechanism effects of nZnO on this plant, others physiological, biochemical and genetics parameters must be analysed.