The Effect of External Treatment of <i>Arabidopsis thaliana</i> with Plant-Derived Stilbene Compounds on Plant Resistance to Abiotic Stresses

Stilbenes are a group of plant phenolic secondary metabolites, with <i>trans</i>-resveratrol (3,5,4′-trihydroxy-<i>trans</i>-stilbene) being recognized as the most prominent and studied member. Stilbenes have a great potential for use in agriculture and medicine, as they have significant activities against plant pathogens and have valuable beneficial effects on human health. In this study, we analyzed the effects of direct application of stilbenes, stilbene precursor, and stilbene-rich extract solutions to the plant foliar surface for increasing the resistance of <i>Arabidopsis thaliana</i> to various abiotic stresses (heat, cold, drought, and soil salinity). Exogenous treatment of <i>A. thaliana</i> with stilbenes (<i>trans</i>-resveratrol, piceid, and spruce bark extract) and phenolic precursor (<i>p</i>-coumaric acid or CA) during germination resulted in considerable growth retardation of <i>A. thaliana</i> plants: a strong delay in the root and stem length of 1-week-old seedlings (in 1.3–4.5 fold) and rosette diameter of 1-month-old plants (in 1.2–1.8 fold), while the 2-month-old treated plants were not significantly different in size from the control. Plant treatments with stilbenes and CA increased the resistance of <i>A. thaliana</i> to heat and, to a lesser extent, to soil salinity (only <i>t</i>-resveratrol and spruce extract) to drought (only CA), while cold resistance was not affected. Plant treatments with stilbenes and CA resulted in a significant increase in plant resistance and survival rates under heat, with plants showing 1.5–2.3 times higher survival rates compared to untreated plants. Thus, exogenous stilbenes and a CA are able to improve plant survival under certain abiotic stresses via specific activation of the genes involved in the biosynthesis of auxins, gibberellins, abscisic acid, and some stress-related genes. The present work provides new insights into the application of stilbenes to improve plant stress tolerance.