The effect of plastoquinone derivatives on barley (Hordeum vulgare L.) tolerance to zinc oxide particles of different dispersion

Abstract

The plastoquinone derivatives 10-(6'-plastoquinonyl) decyltriphenylphosphonium (SkQ1) and 10-(6'-methyl-plastoquinonyl) decyltriphenylphosphonium (SkQ3) are lipophilic cationic antioxidants which can effectively penetrate cell membranes, targeting mitochondria to provide antioxidant defense in cells. In this study, barley (Hordeum vulgare L.) grown on soil spiked with zinc oxide (ZnO) nanoparticle (NPs) stress treated with SkQ1 and SkQ3 to observe the growth rate and level of expression of oxidative stress-related genes in barley seedlings. The study reported that a concentration of 300 mgL^-1 of ZnO NPs inhibits the growth and development of the root system, while the addition of larger ZnO NPs in a similar concentration did not affect the development of the root. With the addition of SkQ1 and SkQ3, the length and weight of roots of the plants grown on soil treated with 300 mgL^-1 of ZnO NPs remain at the control level, while without the antioxidant, root length and weight decrease by 14% and 12%, respectively, compared to the control indicating an increase in plant resistance under NPs induced stress conditions. In the case of 2000 mgL^-1 of ZnO concentration, size-dependent effects were observed on the length of the roots which decreased by 41.5% and 53.8%, and the weight of the roots by 23.3% and 38.8%, respectively, compared to the control. When plants grown on soil spiked with 2000 mgL^-1 of ZnO NPs along with SkQ1 and SkQ3 treatment, an increase in root length is observed by 14.6% and 17.4%, and dry weight increases by 12.2% and 13.2%, respectively compared to the control. When a similar concentration of ZnO in the form of NPs is added, similar indicators increase by 15.5% and 14.3% in root length and 16.0% and 17.1% in root dry weight, respectively. The level of expression of antioxidant system genes in roots decreases by 10-18 times, and in leaves, it changes only slightly, which proves the effect of plastoquinone derivatives on mitochondria, which in the roots are the main suppliers of ROS.