State of enzymatic antioxidative system and heat resistance of wheat plantlets treated by combination of 24-epibrassinolide and NO donor

The influence of 24-epibrassinolide (24-EBL) and nitric oxide donor sodium nitroprusside (SNP) on the state of antioxidative system and heat resistance of wheat (Triticum aestivum L.) plantlets has been investigated. The treatment with 24-EBL (20–200 nM) or with SNP (0.1–2.0 mM) increased the survival of plantlets after 10-min damaging heating at 46 °C in the water thermostat. The cotreatment with 20 nM of 24-EBL and 0.2 mM of SNP caused more essential protective influence in comparison with the treatment by each compound separately. At the same time, joint influence of high concentrations (200 nM of 24-EBL and 2 mM of SNP) reduced the heat resistance of plantlets. Under the influence of 24-EBL and SNP in concentrations that have protective effect, as well as their combinations, the activity of superoxide dismutase (SOD) in roots increased. After damaging heating, the highest value of SOD activity remained in the variant with cotreatment of plantlets with 20 nM of 24-EBL and 0.2 mM of SNP. The activity of catalase and guaiacol peroxidase (GPX) in plantlets roots increased under the influence of various concentrations of SNP and its combinations with 24-EBL. At the same time, 24-EBL alone did not exert the impact on the catalase activity and caused the decrease in GPX activity. The activity of these enzymes decreased in all variants of experiment after heating. The heat stress caused the increase in the content of lipid peroxidation product malonic dialdehyde. The treatment of plantlets with 24-EBL and also its combination with SNP in low concentrations removed this effect, but in high concentrations, on the contrary, increased it. The conclusion was made that intensifying of protective influence of 24-EBL and SNP on wheat plantlets at their combined application in low concentrations is substantially caused by stabilization of pro-/antioxidative balance.