Peroxisomes in higher plant cells are known to differentiate into at least three different classes, namely, glyoxysomes, leaf peroxisomes, and unspecialized peroxisomes, depending on the cell types. In germinating fatty seedlings, glyoxysomes that first appear in the etiolated cotyledonary cells are functionally transformed into leaf peroxisomes during greening. Subsequently, the organelles are transformed back into glyoxysomes during senescence of the cotyledons. Flexibility of function is a distinct feature of plant peroxisomes. This article briefly describes recent studies of the regulatory mechanisms involved in the changes of the function of plant peroxisomes.