Abstract
Lavandula genus is a considerable medicinal plant in pharmaceutical and cosmetics industries. Considering increasing threat of drought in the world, it is important to identify genotypes which can tolerate drought. It is also important to characterize quantity and quality of essential oils, and tolerance indicators of these genotypes against drought stress. Therefore, an experiment was conducted in Gorgan University of Agricultural Sciences and Natural Resources, Iran, during 2017 and 2018, to investigate these factors. It was a factorial experiment based on randomized complete block design with two treatments, three genotypes (Lavandula angustifolia cv. Hidcote, Lavandula angustifolia cv. Munstead, and Lavandula stricta), and four levels of drought stress (irrigation regimes) (I1: 100–90% (control), I2: 80–70%, I3: 60–50% and I4: 30–40% of field capacity) which was done with three repetitions. Drought increased amount of proline in leaves, antioxidant activity, activity of catalase, peroxidase, ascorbate peroxidase, and superoxide enzymes, malondialdehyde content, total flavonoids, total phenol, total sugar and essential oil percentage. The PCA analysis of different irrigation regimes showed that in the first component, the best traits are antioxidant enzymes CAT, SOD, APX, while in the second component, only the trait Catalase is the best trait. The results of PCA analysis in lavender genotypes showed that L. stricta exhibits the most affected physiological changes while trying to adjust to changes in the water status of the environment, under the imposed conditions and shows the highest resistance. But it reduced dry weight of aerial parts, relative water content of leaves, and efficacy of essential oil. Lavandula stricta genotype had the highest amount of essential oil, but the highest dry weight of the aerial parts and essential oil yield were related to L. angustifolia cv. Hidcote and L. angustifolia cv. Munstead genotypes. In all evaluated genotypes, with increasing drought stress, monoterpene compounds were decreased and sesquiterpene compounds were increased. Totally it was shown that drought effect on evaluated traits depends on genotype and nature of traits; this indicates that by choosing drought-tolerant genotypes in breeding programs, high quantity and quality of essential oil, as well as tolerance to drought stress can be achieved.
Highlights
Lavandula genus is a considerable medicinal plant in pharmaceutical and cosmetics industries
Other studies have emphasized that volatile organic compounds (VOCs) biosynthesis is mostly influenced by multiple biotic and abiotic agents and researchers have focused to modified essential oils (EO) quality and quantity through the studies of the molecular mechanisms involved in plant-environment interactions[4, 9]
Dry weight of aerial parts was significantly affected by drought stress and genotype treatments and their interactions (Table 2)
Summary
Lavandula genus is a considerable medicinal plant in pharmaceutical and cosmetics industries. It is important to characterize quantity and quality of essential oils, and tolerance indicators of these genotypes against drought stress. The results of PCA analysis in lavender genotypes showed that L. stricta exhibits the most affected physiological changes while trying to adjust to changes in the water status of the environment, under the imposed conditions and shows the highest resistance It reduced dry weight of aerial parts, relative water content of leaves, and efficacy of essential oil. Abbreviations EO Essential oil APX Ascorbate peroxidase POX Peroxidase ROS Reactive oxygen species SOD Superoxide dismutase CAT Catalase MDA Malondialdehyde LRWC Leaf relative water content DPPH 1,1-Diphenyl-2-picrylhydrazyl H Lavandula angustifolia Cv. Hidcote M Lavandula angustifolia Cv. Munstead gau.ac.ir. Other studies have emphasized that volatile organic compounds (VOCs) biosynthesis is mostly influenced by multiple biotic and abiotic agents and researchers have focused to modified EO quality and quantity through the studies of the molecular mechanisms involved in plant-environment interactions[4, 9]
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