Effect of Selenium on Morpho-Physiological, Phytochemical and Antioxidant Responses to Drought Stress in Hyssopus officinalis L

Selenium (Se), as a vital stress ameliorant, possesses a beneficial effecton moderating detrimental effects of environmental threats. Hyssopus officinalis L. is a popular medicinal herb with carminative, tonic, antiseptic, and expectorant properties and is used to remedy congestion, lung complaints, and cardiovascular disorders. The purpose of this study was to investigate the functions of Se on the morpho-physiological, phytochemical and antioxidant characteristics in Hyssopus officinalis L. subjected to PEG- induced drought stress. For this study, a completely randomized design with three replications was used. The experimental treatments included three concentrations of PEG (Control, -0.3 MPa and -0.6 MPa) as the first factor, sodium selenate at three concentrations (0, 20 and 40 mg L-1) as the second factor and their combined effects. The present study has revealed that Se-supplemented water-deficit plants showed better protection from oxidative damage and this ability was associated with enhancing secondary metabolites, antioxidant potential, osmotic regulators (proline and carbohydrate), defense-related phytohormone (ABA) and vitamine C. Increased hyssop growth under drought stress is attributed to the antioxidant property of selenium. Also, Se mitigated the negative effects of drought by improving the membrane stability index and relative water content. A single foliar selenium application was seen to be less effective than multiple treatments (Se+DS). This indicates a positive interaction or synergistic interaction between DS and Se application. According to our results, applying Se enhanced the EO content and improved EO quality by increasing hyssop’s main EO constituents. The obtained results proposed that Se promoted the morpho- physio-biochemical features of hyssop plants and supported them for cope on drought stress. Therefore, its use may be recommended under arid and semiarid regions.