Silicon-Mitigated Effect on Zinc-Induced Stress Conditions: Epigenetic, Morphological, and Physiological Screening of Barley Plants

Plants are increasingly exposed to stress-induced factors, including heavy metals. Zinc, although it is a microelement, at high concentrations can be phytotoxic to plants by limiting their growth and development. The presented research confirmed the inhibition effect of Zn on morphological and physiological parameters in barley plants. However, the effect was Zn dose dependent (50 µM, 100 µM, and 200 µM), as well as part of the plants (above ground or roots). To mitigate the negative effects of Zn, plants were sprayed with 0.1% silicon. Silicon was proven to have a positive effect on mitigating the inhibitory effects of Zn-induced stress. In most cases, an increase in both morphological (length, elongation, fresh and dry weights, and weather content) and physiological (relative chlorophyll content and fluorescence) parameters was observed. This occurrence was dependent on the Zn dose. Epigenetic analyses confirmed differences in the DNA methylation level, both between plants subjected to stress at different strengths (50 µM, 100 µM, and 200 µM Zn) and between plants sprayed with Si or not. The differences indicate that silicon affects the epigenome of barley plants, thereby modifying the response of plants to stress factors. This modification may be the basis for plants to acquire resistance as "epigenetic memory".