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The aim of the study was to determine the influence of jasmonic acid added to culture medium on the growth of plants and antioxidant properties of dry plant material, as well as on the antimicrobial properties of essential oils produced by the narrow-leaved lavender. For plant propagation, MS media supplemented with JA at concentrations of 0.2-1.5 mg dm−3 were used. The use of the lower JA concentrations did not influenced the growth parameters measured, whereas at the higher concentrations (1 and 1.5 mg dm−3) JA caused growth inhibition and a decrease in plant weight. With increasing JA concentration, the number of secretory trichomes decreased. Addition of 0.5 mg dm−3 JA caused an increase in secretory trichome diameter on both the adaxial and abaxial surface of leaves (83.3 and 73.2 μm, respectively). The antioxidant activity of the lavender plants propagated on media with the addition of JA (regardless of the concentration used) was higher than that of the control plants. The plants from JA-supplemented media were used to isolate essential oils, the antimicrobial activity of which was tested using the disc diffusion method at the concentrations of 10 and 50%. All the oils tested exhibited activity towards Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis and Candida albicans. The essential oils isolated from the plants propagated on the medium with 1 mg dm−3 JA were characterized by the highest antimicrobial activity against the majority of the tested microorganisms.

In the study, micropropagation of three varieties of Lavandula angustifolia was developed, and the appearance of trichomes, antioxidant activity of extracts and antimicrobial activity of essential oils isolated from plants growing in field conditions and in vitro cultures were compared. The study evaluated the number of shoots, and the height and weight of the plants grown on media with additions of BAP, KIN and 2iP. The greatest height was attained by the lavenders growing on MS medium with the addition of 1 mg dm-3 2iP - ‘Ellagance Purple’. The greatest number of shoots was developed by the ‘Ellagance Purple’ and ‘Munstead’ plants growing on the medium with 2 mg dm-3 BAP. The highest weight was attained by the plants growing on the medium with the highest concentration of BAP - 3 and 5 mg dm-3. Moreover, the present study determined the influence of media with the addition of different concentrations of IBA and media with a variable mineral composition (½, ¼, and complete composition of MS medium) and with the addition of IBA or NAA for rooting. The majority of the media used had a positive influence on the development of the root system. The longest root system was observed in ‘Ellagance Purple’ growing on the medium composed of ¼ MS with 0.2 mg dm-3 NAA. All the examined oils exhibited activity towards S. aureus, S. epidermidis, P. aeruginosa, E. coli and C. albicans. The majority of the essential oils isolated from the plants propagated in vitro exhibited stronger antimicrobial activity than the field-grown plants. The plants propagated under in vitro conditions demonstrated considerably higher antioxidant activity as compared with the field-grown plants, which was determined using the DPPH, FRAP and ABTS assay.