The introduction of edible flowers into our menu and their consumption significantly increases as a result of decorative, taste or aroma qualities. Current research on the chemical composition of edible flowers indicates a high content of vitamins, mineral compounds, essential oils, fibre, mucilage and other compounds characterized by a very high antioxidant activity. The aim of the experiment was to compare the nutritional value and antioxidant activity of three annual and two perennial ornamental plant species with edible flowers: Mimulus x hybridus L. ‘Magic Yellow’ and ‘Magic Red’, Antirrhinum majus L. ‘Cavalier’, Dianthus chinensis L. ‘Chianti’, Hemerocallis x hybrida Hort. and Monarda didyma L. Among the edible flower species compared in the study, M. didyma L. showed the highest nutritional value and antioxidant activity (DPPH and ABTS). While flowers of D. chinensis L. ‘Chianti’ were characterized by highest content of antioxidants such as L-ascorbic acid, total anthocyanins, total polyphenols and ferric reducing antioxidant power (FRAP), H. × hybrida and A.  majus L. ‘Cavalier’ flowers – by the highest content of total soluble sugars and sugar/acid ratio, and M. × hybridus L. ‘Magic Red’ and ‘Magic Yellow’ – by the highest content of total carotenoids.

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Biopolymers have become increasingly popular as biostimulators of plant growth. One of them, oligo-alginate, is a molecule that regulates plant biological processes and may be used in horticultural practice as a plant growth regulator. Biostimulators are mainly used to improve plant tolerance to abiotic stresses, including salinity. The aim of the study was to assess the effects of salinity and oligo-alginate of various molecular masses on the growth and physiological activity of Eucomis autumnalis. The species is an ornamental and medicinal plant that has been used for a long time in the traditional medicine of South Africa. The bulbs of E. autumnalis were coated using depolymerized sodium alginate of molecular mass 32,000; 42,000, and 64,000 g mol−1. All of these oligo-alginates fractions stimulated plant growth, and the effect was the strongest for the fraction of 32,000 g mol−1. This fraction was then selected for the second stage of the study, when plants were exposed to salt stress evoked by the presence of 100 mM NaCl. We found that the oligo-alginate coating mitigated the negative effects of salinity. Plants treated with the oligomer and watered with NaCl showed smaller reduction in the weight of the above-ground parts and bulbs, pigment content and antioxidant activity as compared with those not treated with the oligo-alginate. The study demonstrated for the first time that low molecular mass oligo-alginate may be used as plant biostimulator that limits negative effects of salinity in E. autumnalis.

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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 . 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.