The effect of foliar application of abscisic acid on increasing drought stress tolerance in Lavandula angustifolia cv. Munstead Organic

The medicinal plant Lavender (Lavandula angustifolia) is cultivated all over the world due to its economic and ornamental potential and its wide application in the cosmetic and pharmaceutical industries. To investigate the effect of abscisic acid foliar application on increasing drought stress tolerance in Munstead Organic cultivar, a factorial experiment was conducted in a randomized complete block with three replications in the Faculty of Plant Production of Gorgan University of Agricultural Sciences and Natural Resources, Iran in year 2016-2017. Experimental treatments were considered at four levels of irrigation regimes (including 90-100, 70-80, 50-60, and 30-40% of field capacity(FC)) and three levels of abscisic acid foliar application (including zero, 15, and 30 mM/l). Data analysis showed that the highest percentage of the essential oil (1.18%) was obtained in 15 μM abscisic acid and 30-40%FC. While the highest yield of the essential oil (0.055 g/plant) was related to the application of 30 μM abscisic acid in 70-80%FC. The category of the essential oil components also showed that out of 26 identified components, six compounds were hydrocarbon monoterpene, 10 compounds were oxygen monoterpene, six compounds were hydrogen peroxide and four components were oxygen sedimentation. With increasing drought, stress, the amount of hydrocarbon and oxygen monoterpene compounds decreased, but hydrocarbon and oxygen sesquiterpene compounds increased. The results also showed that the highest amount of limonene (10%) was obtained from adding 15 μM abscisic acid in irrigation of 70-80%FC. The highest amounts of camphor (10.47%) and bernoulli (51.58%) were achieved in complete irrigation and non-use of abscisic acid. However, the highest amounts of cariofillenoxide (7.80%) and α-Muurolene (24.90%) was observed in 30 μM abscisic acid and 60-50%FC and in 30 μM abscisic acid and 30-40%FC, respectively. Overall, it was found that foliar application of abscisic acid under drought stress 30-40%FC, could increase the percentage of the essential oils and sesquiterpene compounds to cope with drought conditions in lavender.