Yu. E. Kolupaev^1,2, E. N. Firsova¹, Т. О. Yastreb¹

¹V.V. Dokuchaev Kharkiv National Agrarian University, Ukraine;
e-mail: plant_biology@ukr.net;
²V.N. Karazin Kharkiv National University, Ukraine

The participation of enzymatic systems carrying out generation and conversion of reactive oxygen species (ROS), in realization of the stress-protective effect of hydrogen sulfide (H₂S) on wheat coleoptile cells was investigated. It has been shown that the treatment of isolated coleoptiles with a 100 μM hydrogen sulfide donor sodium hydrosulfide (NaHS) caused a transient enhancement of the generation of superoxide anion radical (O₂^•–), an increase of hydrogen peroxide content and superoxide dismutase (SOD) activity in them. The increase in ROS generation was eliminated by the inhibitor of NADPH oxidase imidazole, but not by the peroxidase inhibitor sodium azide. Treatment of coleoptiles with SOD inhibitor sodium diethyldithiocarbamate (DDC) enhanced the generation of O₂^•– and neutralized the effect of increasing H₂O2 content induced by NaHS. One day after treatment with the H₂S donor, the generation of ROS decreased to a control level, while the activity of antioxidant enzymes increased markedly and the resistance of coleoptiles to damaging heating­ was increased. These effects of the hydrogen sulfide donor were eliminated by coleoptiles’ treatment with inhibitors of NADPH oxidase (imidazole) and SOD (DDC). It was concluded that both NADPH oxidase, genera­ting O₂^•– , and SOD, which turns it into H₂O₂ performing signaling functions, are involved in the formation of a signal that induces protective systems and causes an increase in heat resistance of plant cells.