A BIOCHEMICAL AND CYTOCHEMICAL STUDY OF THE CUTICLE-ASSOCIATED PEROXIDASES IN LUPINUS

A biochemical and cytochemical study of peroxidases (EC 1.11.1.7) associated with the outermost cell layers of Lupinus albus hypocotyls has been performed. Cytochemical investigations showed that in the epidermis of lupin hypocotyls, peroxidatic activities could be detected mainly at the level of the endoplasmic reticulum, Golgi apparatus, ground substance of the cytoplasm, intercellular spaces between adjacent epidermal cells, and in the cuticle layer. No peroxidatic reactions were seen at the level of either the radial or the tangential walls. The cuticle peroxidatic reaction was due to two acidic isoperoxidases, also found in cell walls of vascular tissues, and was further characterized through a study of its catalytic activities. These studies showed that cuticle-associated peroxidases were able to oxidize genistein, but unable to oxidize ascorbic acid. These results suggest that extracellular peroxidases associated with the outermost cell layers of lupin hypocotyls are involved more in the metabolism of isoflavones of the cuticle layer than in the growth responses of the whole organ. © 1991 Annals of Botany Company.