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.

Salvia coccinea (Lamiaceae) is a promising source of potential antioxidants, and its extracts can be used in pharmaceutical industry, as well as in food products and cosmetics. Salicylic acid (SA) affects many physiological and metabolic processes in vascular plants under salinity stress. The aim of this study was to investigate the response of S. coccinea to either SA, or sodium chloride (NaCl), or a combination of both. The plants were sprayed with a solution of 0.5 or 1.0 mM SA and watered with 0, 100, 200, or 300 mM NaCl. Exogenous application of SA increased the number of branches, fresh herbal weight, and total chlorophyll content vs control plants. Salinity-exposed plants showed reduced growth, content of photosynthetic pigments total polyphenols, and antioxidant activity. However, foliar application of SA relieved the adverse effects of 100 mM NaCl, as demonstrated by increased number of branches, greater fresh herbal weight, higher content of total chlorophyll, total carotenoids, and total polyphenols, as well as antioxidant potential, detected using ferric-reducing ability of plasma (FRAP) and 2.2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), compared with untreated plants.

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.

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.

The growing market demand for plant raw materials with improved biological value promotes the extensive search for new elicitors and biostimulants. Gellan gum derivatives may enhance plant growth and development, but have never been used under stress conditions. Perilla (Perilla frutescens, Lamiaceae) is a source of valuable bioproducts for the pharmaceutical, cosmetic, and food industries. However, there is not much information on the use of biostimulators in perilla cultivation. In this work we investigated the effects of oligo-gellan and salt (100 mM NaCl) on the yield and quality of red perilla (P. frutescens var. crispa f. purpurea) leaves. Plants grown under stress showed inhibited growth, smaller biomass, their leaves contained less nitrogen, phosphorus, potassium, total polyphenol and total anthocyanins, and accumulated considerably more sodium than control plants. Treatment with oligo-gellan under non-saline conditions stimulated plant growth and the fresh weight content of the above-ground parts, enhanced the accumulation of nitrogen, potassium, magnesium and total polyphenols, and increased antioxidant activity as assessed by DPPH and ABTS assays. Oligo-gellan applied under saline conditions clearly alleviated the stress effects by limiting the loss of biomass, macronutrients, and total polyphenols. Additionally, plants pretreated with oligo-gellan and then exposed to 100 mM NaCl accumulated less sodium, produced greater amounts of photosynthetic pigments, and had greater antioxidant activity than NaCl-stressed plants. Irrespective of the experimental treatment, 50% extract effectively inhibited growth of Escherichia coli and Staphylococcus aureus. Both microorganisms were the least affected by 25% extract obtained from plants untreated with either NaCl or oligo-gellan. In conclusion, oligo-gellan promoted plant growth and enhanced the quality of red perilla leaves and efficiently alleviated the negative effects of salt stress.