Medicinal plants are rich sources of secondary metabolites. Lepidium sativum possesses active compounds and secondary metabolites, including polyphenol, anthocyanin and flavonoid compounds, which have special pharmaceutical and economic importance. Melatonin, as a bio-stimulator compound, has a regulatory role on the amount of secondary metabolites and plant tolerance facing environmental stresses. In this study, the effect of exogenous melatonin on secondary metabolites production on Lepidium

more »

... ativum was investigated in a completely randomized design with five melatonin treatments (0, 5, 10, 50 and 100 μM) in 3 replications. After applying each treatment, the growth rate and the content of the photosynthetic pigments, the leaf water content as well as the content of flavonoids, anthocyanins and total phenolic compounds investigated. The results indicated that seeds treated with melatonin, especially at concentrations of 50 and 100 μM, showed improvement in the growth parameters and the content of photosynthetic pigments. High levels of melatonin also increased the plant's secondary metabolites, including anthocyanins, carotenoids and plant phenolic compounds. These effects confirm the role of melatonin as a growth regulator and its impact on plant growth and resistance.