A Mechanocomposite Based on Biogenic Silica and Green Tea Flavonoids Modulates Adaptability of Strawberry Microclones to In Vitro and Ex Vitro Conditions

The purpose was to assess effects of a mechanocomposite (MC) based on biogenic silica and green tea flavonoids in terms of alleviation of the impact of abiotic stressors on strawberry plantlets at different stages of clonal micropropagation. An experiment was set up with or without MC treatment at multiplication, in vitro rooting, and ex vitro acclimation stages. We quantified hydrogen peroxide (H 2 O 2 ) as a marker of oxidative stress along with antioxidants (non- and enzymatic), phytohormones, and biomass parameters. At the multiplication stage, MC treatment increased the level of endogenous H 2 O 2 (2.3-fold), the activity of antioxidant enzymes (superoxide dismutase, catalase, and peroxidase), and the total phenolic content. Nonetheless, the MC decreased levels of phytohormones (indole-3-acetic acid, trans-zeatin, and abscisic acid). The addition of MC at the in vitro rooting stage lowered the H 2 O 2 content 1.6-fold, while the activity of antioxidant enzymes significantly increased, compared to the MC-free group; in the MC group, the studied phytohormones showed maximum values. Effects of the MC on phenolic compounds varied. Concentrations of some compounds significantly increased, while the majority of these compounds showed a decline. At the ex vitro acclimation stage, MC treatment raised the level of H 2 O 2 in microshoots in comparison to in vitro stages (this effect was attributed to the enhancement of antioxidant enzymes’ activities), accompanied by downregulation of the phytohormones and upregulation of most of phenolic compounds. The MC-induced effects on growth and development were confirmed by greater shoot biomass. During micropropagation, MC application allows plants to overcome oxidative stress through modulation of activities of antioxidant enzymes and phytohormone levels and a realignment of the profile of phenolic compounds.