It is known that environmental stresses can have devastating effects on plants and represent the most limiting factors for productivity. Apart from biotic stress caused by plant pathogens, there are a number of abiotic stresses such as extremes in temperature, drought, salinity, heavy metals, radiation and mechanical wounding which have detrimental effects on plant growth and development. Certain plant species have developed various mechanisms to defence or adapt to such stress conditions.

Nitric oxide (NO) is a free radical that has been extensively studied as a substance causing air pollution and the product of metabolism of certain groups of bacteria. Ways to download it, metabolism and harmful effects on plants are well established. It turned out , however, that not only the plants respond to changes in the NO concentration in the environment, but they are in a position to produce it .