Effect of Exogenous Application of Ascorbic Acid on some Physiochemical Changes in Oregano (Origanum majorana L.) under Salt Stress

The present study was conducted to evaluate the effect of Ascorbic Acid (AsA) as an important antioxidant in alleviation of salt damage in oregano (Origanum majorana L.). This research work was carried out at the Research Greenhouse of Ferdowsi University of Mashhad. Foliar application of AsA (0, 100, 200 mg/l) was carried out on the plants that were under salt stresses of 0, 50, 100 and 150 mM of NaCl. A factorial experiment, based on a Completely Randomized Design with three replications was adopted and conducted in 2010. The salinity significantly affected the plant's physiochemical characteristics (electrolyte leakage, chlorophyll content, proline, total carbohydrates, antioxidant activity, phenolic compounds) throughout the experiment. The highest electrolyte leakage occurred under the highest level of NaCl (150 mM). Electrolyte leakage decreased by 52% through exogenous application of AsA (200 mg/l), and this occurred via a protection of plasma membrane against adverse effects of salinity. AsA increased the chlorophyll content, carbohydrate and phenolic compounds respectively by 65%, 60% and 38% in comparison with control. Thus, it seems that AsA is more effective in scavenging of free radicals under severe salt stress, by an induction of antioxidant activity to an extent 5-times higher, as compared with control, and so, helps enhancement of plant survival.