For the first time in the history of mankind, man has a realistic possibility of countering millenia of apparently selfish exploitation of nature by the application of scientific knowledge to devise effective remediation schemes. This review concerns the potential of phytoremediation, i.e. the use of plants to neutralize harmful toxic substances. The broad strategy of the plant when confronted by a xenobiotic is to oxidize it, thereby enabling its insertion into standard metabolic cycles (including its ultimate degradation carbon dioxide). Compounds which cannot be oxidized are rendered harmless by conjugation to hydrophilic compounds available within the cell, which not only decreases the toxicity of the xenobiotic, but facilitates its movement to depositories such as the vacuole. The oxidative enzymes act not only to oxidize xenobiotics, but also to hydroxylate them so that they can be conjugated. Hydroxylation is catalyzed by metalloenzymes: cytochrome P450-containing monooxygenases, peroxidases and copper-containing polyphenoloxidases. Cytochrome P450 is characterized by very low specificity, enabling it to treat an extraordinarily wide range of organic compounds. Under certain conditions plant microsomal cytochrome P450 loses its monooxygenase activity and becomes a peroxidase: this switching is an example of the sophisticated ability of plants to adapt to stress.

Keywords: conjugation, cytochrome P450, malate dehydrogenase, monooxygenases, oxidative enzymes, peroxidase, polyphenoloxidase, xenobiotics, ultrastructural reorganization