Cytokinins Contribute to Realization of Nitric Oxide Growth-Stimulating and Protective Effects on Wheat Plants

We investigated effects of sodium nitroprusside (SNP), the donor of nitric oxide (NO), on the growth and hormonal system of wheat plants (Triticum aestivum L.) in normal conditions and after salt stress (2% NaCl). During germination of seeds treated with SNP (50-500 mu M), we obtained the SNP concentration (200 mu M) optimal for stimulation of seedling growth estimated by increase in seed germination capacity and seedlings' linear sizes and their fresh and dry biomass. A comparative analysis of SNP (200 mu M) effects, after seed germination in the medium with SNP or pretreatment of 3-day-old seedlings, showed SNP ability to increase the wheat plant resistance to subsequent effects of sodium chloride salinity at both treatment methods. Protective SNP effects appeared in the reduction of stress inhibitory action on seedling growth rates and significant reduction in the level of lipid peroxidation and exosmosis of electrolytes. An important contribution to realization of the growth-stimulating and protective effects of NO is associated with its ability to influence the state of the hormonal system of wheat plants due to an increase in the concentration of hormones of a cytokinin nature under normal conditions and the prevention of a decrease in their level under stress.