Seed priming with melatonin effects on growth, essential oil compounds and antioxidant activity of basil (Ocimum basilicum L.) under salinity stress

Melatonin has been reported to exhibit significant functions in plant growth and development in response stress conditions. Along with the present study, the effects of melatonin priming on plant growth and development, essential oil, phenolic acids and antioxidant activities of basil (Ocimum basilicum L.) under salinity were examined. In this context, the seeds were firstly primed with 1 and 10 μM melatonin and subsequently plants were exposed to salinity stress from 100 mM NaCl. The results showed that salinity decreased all growth parameters except leaf number and melatonin treatments were effective in all parameters under stress groupsbut depending on the dose applied. According to GC–MS/FID results, of the major compounds, eugenol and methly eugenol exhibited decreases whereas linalool increased under salinity. Furthermore, rosmarinic acid, cichoric acid and caffeic acid were identified as major phenolics with HPLC analyses. Under salinity, rosmarinic acid was not detected, cichoric and caffeic acids were decreased while 10 μM melatonin treatments increased all phenolic acids. Salt stress and melatonin applications except salinity with 10 μM melatonin decreased DPPH antioxidant activity, total phenolics and total flavonoids. The salinity with 10 μM melatonin addition favoured for total phenolics and flavonoids.