The purpose was to assess the effects of a biostimulant based on silicon chelates in terms of alleviation of the impact of in vivo conditions on strawberry (Fragaria × ananassa cv. ‘Solnechnaya polyanka’) in-vitro-derived plants. As a source of silicon chelates, a mechanocomposite (MC) obtained through mechanochemical processing of rice husks and green tea was used. Root treatment of plants with 0.3 g L⁻¹ of MC dissolved in tap water was performed at 2 weeks after planting. Control plants were watered with tap water. The greatest shoot height, number of roots per plant, root length, number of stolons per plant, daughter ramets per stolon, relative water content, cuticle thickness, and root and shoot biomasses were achieved with the MC supplementation. The improved parameters were associated with a higher silicon content of roots and shoots of the MC-treated plants. Leaf concentrations of hydrogen peroxide and abscisic acid were reduced by the MC. This effect was accompanied by enhanced activity of superoxide dismutase and catalase. The phenolic profile showed upregulation of p-hydroxybenzoic acid, vanillic acid, gallic acid, syringic acid, and ellagic acid derivative 2, while kaempferol rutinoside and catechins were downregulated. Thus, silicon chelates improve growth and trigger the physiological processes that enhance free-radical-scavenging activity in strawberry plants in vivo.

In this study, growth parameters of underground parts and concentrations of phenylpropanoids, phenylethanoids, flavonoids, hydroxybenzoic acids, and catechins in aqueous–ethanol extracts of 6-year-old cultivated plants of Rhodiola rosea (propagated in vitro) of Altai Mountain origin were analyzed, and differences in chemical composition among plant specimens and between plant parts (rhizome and root) were evaluated. High-performance liquid chromatography detected 13 phenolic compounds. Roots contained 1.28 times higher phenylethanoids levels (1273.72 mg/100 g) than rhizomes did. Overall, the concentration of phenylethanoids in underground organs was not high and ranged from 21.36 to 103.00 mg/100 g. High variation among R. rosea individual plants was noted both in growth characteristics and in levels of secondary metabolites under our cultivation conditions. It was found that concentrations of phenylpropanoids, phenylethanoids, and catechins significantly depend on the plant part analyzed (p ≤ 0.05). Specimen No. 4 is characterized by the highest concentration of rosavins (1230.99 mg/plant) and the lowest concentration of cinnamyl alcohol (62.87 mg/plant). Despite the wide range of values, all 10 tested specimens (underground part) met the minimum requirements of the United States Pharmacopeia (2015) for rosavins (0.3%) and of the Russia State Pharmacopoeia (2015) for the average level of rosavins (roots): (1%).

The positive effect of silicon on plants is thought to be mediated by a modification of phenolic metabolism. The purpose of the study was to evaluate the effect of a silicon-based mechanocomposite (MC) on alterations of the phenolic profile of strawberry plants in the course of development under in vitro, ex vitro, and in vivo conditions. Aqueous ethanol extracts of aboveground parts of in vitro–derived plants (Fragaria × ananassa cv. ‘Solnechnaya polyanka’) were subjected to HPLC. Nineteen individual phenolic compounds (hydroxybenzoic and hydroxycinnamic acids, catechins, ellagic acid derivatives, and flavonol glycosides) were quantified. The results revealed phenolic profiles specific to each studied stage and significant transformations of the profiles by the MC. It induced strong upregulation of hydroxycinnamic acid during in vitro rooting and of catechins and hydroxybenzoic acids during ex vitro acclimation. At ex vitro and in vivo stages, the emergence of quercetin glycosides and ellagitannins was registered, and the MC elevated their levels during ex vitro acclimation and field growth. Principal component analysis confirmed the significant effect of the MC on the phenolic profile at all stages, and this effect was the strongest during ex vitro acclimation. The results are consistent with previous reports on the modification of phenolic profiles of plants by silicon-derived biostimulants.