ABSTRACT
This chapter shows that an increase in the levels of certain enzymes is necessary to permit the expression of anoxic tolerance. Enzyme modifications may also occur in response to oxygen deprivation. Plant adaptations to oxygen deficit can be divided into those that allow the avoidance of oxygen deficits, such as the formation of aerenchymas, and those that permit adaptation. Under conditions of oxygen deficit, ten major and ten minor polypeptides were synthesized in maize primary roots. Enzymes induced by oxygen deficit can be divided into several groups. These are enzymes involved in the mobilization of carbohydrates; enzymes involved in glycolysis; enzymes responsible for fermentation; enzymes involved in aerenchyma formation; and enzymes implicated in pH regulation. In conclusion, the maintenance of the high glycolytic flux during anoxia that is essential for the expression of tolerance mainly depends on increasing the levels of many, if not all, the enzymes involved, through gene activation.
