Effects of chitosan foliar application on some physiological and biochemical traits of thyme (Thymus vulgaris L.) under drought stress

To investigate the effects of chitosan foliar application on the various physiological and biochemical (proline, protein, antioxidant enzymes, and percentage and essential oil yield) characteristics and dry matter yield of thyme (Thymus vulgaris L.) under drought stress conditions, a split-plot experiment was conducted in a randomized complete block design with three replications in Lalehzar city, Bardsir county, Kerman province in 2019. The drought stress at four levels (35, 50, 65, and 80% of available moisture discharge) and the chitosan concentration at five levels (0, 0.2, 0.5, 1.0, and 1.5 gram chitosan per liter of acetic acid) were considered as the main and sub plots, respectively. The results showed that the drought stress increased proline, antioxidant enzymes, and percentage and essential oil yield and decreased the dry matter yield significantly. The proline, antioxidant enzymes, dry matter yield, and essential oil percentage increased significantly with increasing the chitosan concentration, which resulted in a significant increase in the essential oil yield as the most important quality index in thyme. The protein and gayacol peroxidase enzyme were not affected by chitosan foliar application. In general, the results of this research showed that the higher chitosan concentrations (1.5 gram chitosan per liter of acetic acid) were more effective in ameliorating the damages induced by the drought stress and achieving the higher yield.