Effect of salicylic acid application on some growth traits of Lemon verbena (Lippia citriodora) under salinity stress

The citriodora Lippia is a shrub of the Verbenaceae family which cultivated in many countries due to its high economic importance. The leaves of this plant as usable part of the plant have essential oils.This essential oil is very valuable in the perfume industry. In addition, the dry leaves of this plant are used as a herbal tea. One of the problems in Iran's soils is the presence of salt stress, which is one of the major limiting factors for agricultural production. Due to the economic significance of Lemon verbena, and the salinity problem that could restrict the cultivation of this plant, this study was conducted.

In this study, the effect of different concentrations of salicylic acid on salinity tolerance Lemon verbena were investigated. Factors included salinity in four levels (0, 50, 100 and 150 mM sodium chloride) and salicylic acid at three levels (0, 0.5, 1 mM) with 3 replications.

The results showed that salinity effect on all parameters was significant except for the relative water content of leaves. The effect of salicylic acid on all parameters except leaf dry weight, leaf relative water content and activity of peroxidase enzyme was significant. In salinity stress conditions, leaf dry weight, stem height, chlorophyll content decreased significantly. The percentage of weight loss in treatments 50, 100 and 150 mM was 10.36, 24.4 and 30.12%, respectively. The highest amount of proline, carbohydrate, antioxidant enzymes and ion leakage was observed in severe stress treatments. So that the highest ion leakage (78.77%) belonged to salinity 150 mM and the lowest amount (52.55%) was obtained in no salinity conditions. The difference between treatments of salinity of 50 and 100 mM was not statistically significant. Application of salicylic acid increased stem height, activity of antioxidant enzymes, chlorophyll, carbohydrate, proline and essential oil percentage. The concentration of 1 mM salicylic acid significantly increased stem height, soluble sugars, chlorophyll content and proline and reduced the amount of ion leakage of seedlings in Lemon verbena compared to non-foliar application. The highest activity of catalase (95.09 u / mg.fw-1) and peroxidase (26.47 u / mg.fw-1) was observed in salinity of 150 mM and concentration of 1 mM salicylic acid. In terms of essential oil content, the results showed that with increasing salinity up to 100 mM, the percentage of essential oil increased. That is, salinity up to 100 mM concentration did not have a negative effect on the essential oil content and even increased it. But with increasing salinity to 150 mM, essential oil content decreased.In general, salicylic acid spraying, especially concentration of 1 mM, could reduce the effect of salinity stress on Lemon verbena seedlings.

In general, salicylic acid spraying, especially concentration of 1 mM, could reduce the effect of salinity stress on Lemon verbena seedlings.