The service tree (Sorbus domestica) is a wild fruit tree with immense medicinal and industrial value. This study aimed at determining the four major groups of antioxidants (flavonoids, phenolic acids and aldehydes, catechin and procyanidin) in rootstocks of Crataegus laevigata (genotypes O-LE-14 and O-LE-21), Aronia melanocarpa (genotypes O-LE-14 and O-LE-21), Chaenomeles japonica (genotype O-LE-9) and Cydonia oblonga (BA 29) (genotypes O-LE-14 and O-LE-21).Hyperoside (Quercetin 3-D-galactoside) was the most abundant flavonoid compound, since its average content in the rootstocks of Crataegus laevigata (O-LE-21) was 180.68 ± 0.04 µg·g −1 . Dihydrokaempherol was the least frequently found flavonoid compound, with an average concentration of 0.43 ± 0.01 µg·g −1 in all the rootstocks of plants considered in this study. Among the phenolic compounds, the most represented one was protocatechuic acid, with 955.92 ± 10.25 µg·g −1 in the rootstocks of Aronia melanocarpa (O-LE-14). On the other hand, the least represented p-Coumaric acid exhibited the average concentration of 0.34 ± 0.01 µg·g −1 in the plant rootstocks. Epicatechin was the most abundant catechin compound, with a content of 3196.37 ± 50.10 µg·g −1 in the rootstocks of Aronia melanocarpa (O-LE-14). The lowest represented catechin compound was epigallocatechin, with the average concentration of 0.95 ± 0.08 µg·g −1 in the screened plant rootstocks. From the procyanidin compounds, the most abundant one was procyanidin b2 in the rootstocks of Crataegus laevigata (O-LE-14), with a concentration of 5550.40 ± 99.56 µg·g −1 . On the contrary, procyanidin a2, with an average concentration of 40.35 ± 1.61 µg·g −1 , represented the least frequent procyanidin compound in all the plant rootstocks screened herein.

Even though silicon is frequent compound in soil, its use in plant nutrient media is rare. Based on known physiological role and up to now performed studies it seems that silicon has a good potential to improve growth characteristics of in vitro cultivated plants. Before practical application, however, it is always necessary to assess the optimal conditions of application with regard to the fact that plant reactions to different chemicals added to nutritional media can vary on the species or even cultivar level. The presented study evaluate effects of potassium silicate used in in vitro cultivation media on growth parameters of Prunus persica × Prunus davidiana ‘Cadaman,‘ Prunus × amygdalopersica ‘GF 677‘ and Corylus avellana ‘Tonda di Giffoni‘ genotypes, which are frequently subject of commercial in vitro multiplication. In fact, four different concentrations of potassium silicate was added to the multiplication media, control medium was left silicon-free. Three different characteristics were observed during cultivation – number of new shoots per explant, weight of a new plant and length of new shoots, from which number of new shoots per explant was considered the most important factor. In all cases a positive effects of potassium silicate on the condition and other growth parameters of treated cultures were observed. In ‘Cadaman‘ culture significant growth changes appeared on media with 20 mg.l-1 potassium silicate, which can be recommended for future applications. For ‘GF 677‘ the best results were obtained on media with 2 mg.l-1 which can be recommended for improving condition and number of shoots on new plants. For hazelnut genotype ‘Tonda di Giffoni‘ best results were obtained on media with 10 mg.l-1 of potassium silicate, but also use of 5 mg.l-1 of potassium silicate significantly improved growth parameters. Generally, presented study provides important and practically useful insights into the practical use of silicon in cultivation media designated for commercial in vitro micropropagation.