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 . This has changed the way of thinking of nitric oxide, which is considered a signaling molecule that plays an important role in signal transduction pathways in plants , which involve the cyclic nucleotides (cAMP , cGMP) , hydrogen peroxide, salicylic acid or calcium ions. The concentration of NO, as the biologically active molecule must be subject to strict regulation at the site of action, which correspond to both the mechanisms leading to the generation and removal . It is known that NO is produced with the participation of nitric oxide synthase from L-arginine , with nitrite, by the action of the nitrate reductase , as well as by non-enzymatic changes ( redox reactions ) , as an intermediate in the process of nitrogen fixation , respiration or denitrification . The process involves the inactivation of a number of compounds , such as the superoxide radical ( O2 - ) , glutathione , metal ions , and transition groups niesymbiotyczna hemoglobin . Operation of NO in the body of the plant is multi-faceted and dependent upon various internal and environmental factors . Its participation has been described in some of morphogenetic processes such as contraction of the stationary phase of seed, the promotion of the germination process and aging of plants, inhibition of flowering, and programmed cell death ksylogeneza , as well as the movements of the stomata . However, the best known was his participation in immune responses to biotic ( pathogen infection ) and abiotic (drought , salinity , high temperatures, exposure to UV light , heavy metals, herbicides , injury ) . The vast majority of stress factors cause an increase in the concentration of NO, the task of reducing the harmful effects of free radicals and reaction with other signal molecules such as salicylic acid, calcium and cyclic GMP . It was also found its share in the modulation of expression of genes involved in stress responses . The purpose of this paper is to present information concerning the metabolism of nitric oxide in plant cells and participation in the reactions of plants to abiotic stress . In addition, evidence of an interaction of NO with other signal molecules in the regulation of stomatal closing in response of plants to stress dehydratacyjny.