Summary: The participation of oxidative enzymes (cytochrome P450-containing monooxygenase, peroxidase and phenoloxidase) in oxidation of model organic xenobiotic – nitrobenzene was investigated. The intracellular localization of above mentioned enzymes were revealed. The contribution of each enzyme in xenobiotic oxidation was established. It has been shown that during reaction another may replace one oxidative system. It was concluded that during xenobiotic hydroxylation the coordination of oxidative enzymatic systems may carried out both by principle of inter replacement of different systems and by modify of cytochrome P450 activity that depended on plant cultivated regimes (illumination), aging, infection and xenobiotic influence.