Interactive effects of melatonin and light on growth parameters and biochemical markers in adventitious roots of Withania somnifera L.

Light plays a pertinent role in plant photo-morphogenesis and it is believed to have an impact on the melatonin-induced physiological functions. In the current study, different light regimes were employed with varying levels of melatonin, either singly or in combination with auxins for the growth and development of adventitious roots in Withania somnifera L. It was observed that 600 A mu M melatonin favored maximum adventitious root induction frequency (58 %) in cultures incubated under continuous dark conditions. However, adequate root growth (number and length of roots) was observed under 16 h light/8 h dark at 600 A mu M melatonin. Nevertheless, the interactive effect of light and melatonin was found stimulating for profound production of commercially important secondary metabolites. Correlation among growth parameters and biochemical markers was also observed in the current report. Data on total phenolic content and total flavonoid content were found at higher coincidence with each other and with DPPH antioxidant activity. In conclusion, exogenously applied melatonin mimics IAA activity in root growth and regulates well in 16-h light/8-h dark, thereby giving protection to plant system against light stress.