Soil salinity is one of the basic factors causing physiological, biochemical and epigenetic changes in plants. The negative effects of salt in the soil environment can be reduced by foliar application of silicon (Si). The study showed some positive effects of Si on maize plants (Zea mays L.) grown in various salinity conditions. At high soil salinity (300 and 400 mM NaCl), higher CCI content was demonstrated following the application of 0.2 and 0.3% Si. Chlorophyll fluorescence parameters (PI, F_V/F₀, F_v/F_m and RC/ABS) were higher after spraying at 0.3 and 0.4% Si, and plant gas exchange (C_i, P_N, g_s, E) was higher after spraying from 0.1 to 0.4% Si. Soil salinity determined by the level of chlorophyll a and b, and carotenoid pigments caused the accumulation of free proline in plant leaves. To detect changes in DNA methylation under salt stress and in combination with Si treatment of maize plants, the methylation-sensitive amplified polymorphism (MSAP) technique was used. The overall DNA methylation level within the 3′CCGG 5′ sequence varied among groups of plants differentially treated. Results obtained indicated alterations of DNA methylation in plants as a response to salt stress, and the effects of NaCl + Si were dose-dependent. These changes may suggest mechanisms for plant adaptation under salt stress.

Paulownia spp. are widely distributed ornamental trees with leaves abundant in secondary metabolites of high medicinal potential. Eighteen breeding clones of Paulownia spp. were tested in terms of their antioxidant activity and total polyphenolic contents. The 50% ethanolic extracts (2 g/30 mL) of leaves and petioles were compared in the screening step. Eight paulownia clones were selected for detailed analyses including HPTLC polyphenolic profile, verbascoside content and antibacterial activity against five bacteria species (S. aureus, B. cereus, E. coli, Y. enterocolitica, S. enterica). The species-specific differences in terms of antioxidant activity correlated with phenolic compounds were found mainly in the case of leaf blade extracts, the highest for P. tomentosa × P. fortunei and the lowest for P. elongata × P. fortunei clones. The P. tomentosa clones varied greatly in this regard. In the HPTLC polyphenolic profile, the occurrence of some polyphenols was proved and the specific verbascoside content was quantified (70 to 225 mg/g DW). The P. tomentosa × P. fortunei hybrids had the highest inhibitory activity, mainly against Gram-positive bacteria, whereas only slight inhibition of S. aureus growth was observed for P. elongata × P. fortunei clones. The obtained results indicate diverse suitability of paulownia clones as a source of active ingredients.

The effects of drought stress on the morphological and physiological features of highbush blueberry Brigitta Blue plants were investigated. The plants were propagated conventionally by stem cutting (SC) and tissue culture (TC). Micropropagated plants originating from axillary (TC-Ax) and adventitious (TC-Ad) shoots were separated. An additional group consisted of plants propagated several times by stem cuttings, derived from TC mother plants (TC/SC). Different concentrations of polyethylene glycol (PEG) (3% and 7%) were applied to induce drought stress. Parameters such as dry and fresh weight, water content, shoot elongation as well as chlorophyll fluorescence and content were measured. The effect of PEG treatment varied in plants of different origin. Shoot elongation was mainly inhibited in SC plants, whereas TC/SC plants exhibited a stronger reduction of photosystem II efficiency. Fm and Fv differences between TC plants propagated by axillary or adventitious shoots were also observed under control conditions. These epigenotypes also differed in shoot elongation under 7% PEG treatment. The obtained results confirmed the influence of the propagation method of highbush blueberry plants not only on morphological traits, but also on the physiological status.

The aim of the study was to examine the effects of application of plant-growth regulators (PGR) on the growth of paulownia plants and evaluate their usefulness in paulownia nurseries. The experiment was carried out on the paulownia interspecific hybrid (Paulownia elongata × Paulownia fortunei) ‘Oxytree’. Micropropagated plants grown in pots were sprayed with PGR solutions. Gibberellins (GA₃, GA₄+GA₇), 6-benzyladenine (BA), triclopyr (TPA), ethephon (ETH), daminozide (DA), prohexadione-Ca (PH), and trinexapac-ethyl (TE) were used. They were included in commercial products (Florgib 245 mg dm⁻³, Gibb plus 11 SL 5 cm³ dm⁻³, Globaryll 100 SL 1.5 cm³ dm⁻³, Topper 10 ST 200 mg dm⁻³, Agrostym 480 SL 2 cm³ dm⁻³, B-Nine 85 SG 2 g dm⁻³, Regalis plus 10 WG 2.5 g dm⁻³, Moddus 250 EC 1 cm³ dm⁻³, respectively). None of the studied preparations modified positive correlations between the longitudinal vs. transverse growth of stems and growth of leaves. Not only GA₃, GA₄+GA₇, but also BA (cytokinin) and unexpectedly TE (retardant) stimulated stem elongation and thickening. Furthermore, the effect of TE lasted longer than influence of GA_x and BA. Leaves of TE-treated plants were distinguished by a higher chlorophyll a/b ratio, and a lower relative chlorophyll content and efficiency of photosystem II (F_v/F_m, F_v/F₀). TPA strongly deformed the stems and leaves of liners. Other regulators (ETH, DA, PH) retarded the diameter growth of stems and leaf expansion. Some results obtained by GA_x, BA, and especially by TE treatment, might be beneficial for paulownia grown as ornamental and/or timber tree.

The aim of the study was to compare two methods of micropropagation of mulberry: single-node culture (“SNC”), and axillary-branching (“AxB”). The experiments were carried out on in vitro cultures for 6 successive passages. The “AxB” cultures were propagated on modified MS medium (+ 25% Ca²⁺ and Mg²⁺), supplemented with WPM vitamins, sucrose (30 g L⁻¹), and BA (1.5 mg l^-1). The “SNC” cultures were grown on cytokinin-free 1/2 MS (macro- and micronutrients) medium supplemented with WPM vitamins, IBA (0.05 mg l^-1), and sucrose (15 g l^-1). Both media (pH 5.8) were solidified with agar (7.0 g l^-1). Initiation of in vitro cultures from explants taken from adult trees and young, potted plants was feasible on both media. Cultures were established from about 1 cm long nodal explants. Generally “SNC” cultures formed one well rooted, significantly longer axillary shoot with bigger leaves than “AxB” cultures, which developed significantly more shoots and big callus at the explant base. All shoots collected from “SNC” and “AxB” cultures rooted in vivo in peat mixture and developed into similar plantlets. The single-node method based on application of cytokinin-free medium is a good alternative for the axillary-branching method for micropropagation of mountain mulberry (Morus bombycis) ‘Kenmochi”’.

Paulownia leaf extracts were tested for their bacteriostatic and antioxidant properties against six pathogenic bacteria in vegetable and fruit crops. Paulownia leaf extracts were most effective against the Clavibacter michiganensis ssp. michiganensis and Xanthomonas hortorum pv. carotae. Paulownia extracts were less effective against Agrobacterium tumefaciens, Pseudomonas syringae pv. lachrymans and Pseudomonas syringae pv. tomato. Only Erwinia carotovora was resistant to the tested plant extracts. The type of extraction solvent significantly impacts the antibacterial activity and the flavonoid and polyphenol contents of plant extracts. Acetone and alcoholic extracts had a higher content of flavonoid and polyphenolic compounds than water extracts, which resulted in their better bacteriostatic properties. The growth inhibition zones of the tested bacteria and the contents of flavonoids and polyphenols were significantly correlated. However, the bacteriostatic properties and antioxidant activity were not significantly correlated.