Effect of stress modifiers on physiological, antioxidant activity and yield characteristics of Thymus vulgaris L under water-deficit stress

To investigate the effect of stress modulators on physiological, antioxidant and yield characteristics of thyme in drought stress conditions, factorial experiment is performed in the form of a randomized complete block design with ۱۰ treatments and ۳ replications in ۲۰۱۹-۲۰۲۰ growing season. Factors included stress modulators at ۵ levels (zinc, amino acid, humic acid, seaweed and control) and irrigation regimen at ۲ levels (irrigation every week and irrigation every two weeks). Based on the results, the interaction of the irrigation every week and humic acid produced the highest total phenol (۲۷.۹۰ mg g-۱ DW), total flavonoids (۱.۴۷ mg g-۱ DW), essential oil yield (۱.۱۸ Kg ha-۱), biological yield (۱۷۸۰.۵۰ Kg ha-۱) and grain yield (۳۷۶.۹۴ Kg ha-۱). Whereas, proline content was higher in the interaction of the irrigation every two weeks conditions and the control plants. Moreover, the simple effects of irrigation every week and humic acid and seaweed treatments showed the highest total chlorophyll (۲.۷۶ mg g-۱ FW) and carotenoid contents (۱.۱۲ mg g-۱ FW), relative water content (۷۸.۴۸ %), the content of phosphorus (۰.۶۶ mg g-۱ DW) and potassium (۱۸.۲۶ mg g-۱ DW), essential oil (۰.۱۷%), oil percentage (۲۵.۹۷%) and oil yield (۱۵۵.۲۸ Kg ha-۱) among which amino acid and zinc with a slight difference had similar effects. The spraying plants with humic acid, seaweed and amino acid in irrigation every week conditions had higher antioxidant activity. So regarding these traits, it is recommended that stress modifiers such as humic acid, seaweed and amino acid can help organic crops expand under water-deficit stress.

Keywords:

Antioxidant , Humic acid , Seaweed , Irrigation , Sustainable agriculture