The effect of exogenously applied plant growth regulators and zinc on some physiological characteristics and essential oil constituents of Moldavian balm (Dracocephalum moldavica L.) under water stress

Esmaeil Rezaei-Chiyaneh; Hassan Mahdavikia; Hashem Hadi; Hadi Alipour; Muhittin Kulak; Gianluca Caruso; Kadambot H M Siddique

doi:10.1007/s12298-021-01084-1

The effect of exogenously applied plant growth regulators and zinc on some physiological characteristics and essential oil constituents of Moldavian balm (Dracocephalum moldavica L.) under water stress

Physiol Mol Biol Plants. 2021 Oct;27(10):2201-2214. doi: 10.1007/s12298-021-01084-1. Epub 2021 Oct 13.

Authors

Esmaeil Rezaei-Chiyaneh¹, Hassan Mahdavikia², Hashem Hadi¹, Hadi Alipour¹, Muhittin Kulak³, Gianluca Caruso⁴, Kadambot H M Siddique⁵

Affiliations

¹ Department of Plant Production and Genetics, Faculty of Agriculture and Natural Resources, Urmia University, Urmia, Iran.
² Department of Medicinal Plants, Shahid Bakeri Higher Education Center of Miandoab, Urmia University, Urmia, Iran.
³ Department of Herbal and Animal Production, Vocational School of Technical Sciences, Igdir University, 76000 Igdir, Turkey.
⁴ Department of Agricultural Sciences, University of Naples Federico II, 80055 Naples, Italy.
⁵ The UWA Institute of Agriculture, The University of Western Australia, Perth, WA 6009 Australia.

Abstract

Cost-effective exogenous application of some antioxidant, viz. salicylic acid (SA) and ascorbic acid (AA), and essential micronutrient elements like Zn might alleviate the harmful impacts of drought stress. Here, we evaluated the interaction of foliar-sprayed SA (1 mM), AA (10 mM), and Zn (3 g L^-1) and irrigation regime (normal irrigation, moderate water stress, and severe water stress) by assaying an array of agronomic, physiological, analytical and biochemical parameters of Moldavian balm (Dracocephalum moldavica L.). Accordingly, the SA and AA treatments reduced the harmful effects of moderate and severe drought stress. Well-watered plants applied with Zn had the highest biomass yield (4642.5 kg ha^-1). Severe water stress decreased plant biomass, essential oil (EO) content, EO yield, relative water content, and chlorophyll a content by 37.6%, 23.3%, 47.5%, 35.3%, and 53%, respectively, relative to normal irrigation. Plants treated with Zn under moderate drought stress had the highest EO content. Moderate and severe water stress increased enzymatic antioxidant (catalase, superoxide dismutase, and peroxidase) activities and total soluble sugars and proline contents. In terms of EO composition, SA-treated plants under moderate water stress contained the most geraniol (22.8%) and geranial (26.3%), while Zn-treated plants under severe water stress contained the most geranyl acetate (48.2%). This study demonstrated that foliar application of Zn and SA significantly improves EO productivity and quality in Moldavian balm under moderate water stress. The relevant findings were supported by heatmap clustering, revealing that irrigation regime had main effect on the essential oil compounds and biochemical and physiological parameters.

Supplementary information: The online version contains supplementary material available at 10.1007/s12298-021-01084-1.

Keywords: Biomass yield; Geranyl acetate; Secondary metabolites; Soluble sugars; Superoxide dismutase; Water deficit.