GENERATION OF NITRIC OXIDE AND ITS ROLE UNDER STRESS CONDITIONS IN PLANTS

Nitric oxide is one of reactive nitrogen species. This form of nitrogen can influence the plant organism both positively and negatively. This work provides available information on the effect of nitric oxide donors on the plant organism. At low concentrations • NO can operate as a signaling molecule with a wide range of regulatory functions. • NO is involved in the response of plants to stressful environmental factors, both biotic and abiotic nature. Specifically, • NO increases plant resistance at exposure to salt stress, heavy metal ions, pathogens, increases tolerance to sudden decrease or increase of the ambient temperature. In this work the mechanisms of nitric oxide formation in various plant organelles are described. Plant organisms also can be affected environmentally derived • NO. Nitrate reductase and NO-synthase are the enzymes involved in • NO formation. Nitric oxide is released from the peroxisomes, chloroplasts and mitochondria. Nitrite can be reduced to nitric oxide in the plant mitochondria. Inhibitors of the mitochondrial electron transport chain (ETC) also inhibit • NO production. That indicate that the electrons from mitochondrial ETC can participate in reduction of nitrite. In peroxisomes • NO is formed by the action of the enzyme NO-synthase. Also non-enzymatic reduction of nitrite in apoplast space as one of the ways of • NO formation in plants, especially in roots, was described. The increase of nitric oxide release can be observed under treatment by herbicides and nitrate fertilizers. In addition, reactive nitrogen species can be received by plants from the environment, particularly as nitric oxide. This review paper presents generalized scheme of effect of nitric oxide and its transformations in plants.