Effect of concentration and type of selenium application on the quantity and quality of essential oil of Lemon verbena (Lippia citriodora L.)

Selenium is a beneficial element with antioxidant and antiviral properties that promotes plant growth. In order to investigate the effect of selenium on some morphological, physiological and quantitative and quality of lemon essential oil, an experiment was conducted with 5 treatments and 3 replications in hydroponic culture system. Selenium in form of sodium selenate was applied either in nutrient solution or by foliar spraying at levels (0, 2.0, 5.0, 10.0 and 15µM). The results showed that selenium treatment significantly increased leaf dry weight, leaf area and total chlorophyll content in both application methods compared to the control. Application of 5 µM Se in nutrient solution and of 10µM Se by foliar spraying successfully enhanced total phenolic compounds and DPPH free radical scavenging in leaves. The lowest amount of malondialdehyde by foliar application (13.4) and addition to nutrient solution (10.7) was observed in 10 and 5 ?M treatments, respectively. Also, this element increased the amount of essential oil in the treatment levels of 5 ?M nutrient solution and 10 ?M foliar application by 94.92 and 100%, respectively, compared to the control treatment. The survey of essential oil components showed that the highest amount of oxygenated monoterpenes, especially citral (48.3%) was measured from foliar samples with a concentration of 10 ?M selenium. In fact, the results of this study showed that the selenium in low concentrations (5-10 ?M) had improving effects on growth, physiological and quantity and quality of essential oils of Lemon verbena.