Inhibition of flavohemeproteins enhances the emission and level of nitric oxide in barley root tips.

In this study, using a pharmaceutical approach, we analyzed the NO accumulation and emission from the root tips of barley seedlings and the possible mechanisms of NO catabolism. Application of flavohemeprotein inhibitors, such as azide, cyanide, diphenyleneiodonium and dicumarol, an inhibitor of the plasma membrane electron transport chain, increased the NO level in root tissue and stimulated the NO emission from root tip cells. It can be concluded that barley root tips generate and, at the same time, consume a considerable amount of NO, probably by the plasma membrane flavohemeproteins. This high NO-consuming activity of barley root tips efficiently degraded even the externally applied high concentrations of NO without marked root growth inhibition. These results suggest that the root tip cells NO consumption activity plays an important role in the regulation of NO level in barley root tips.