Physiological roles have been proposed for several of these enzymes which include a hormone controlled transmembrane WADH oxidase, an iron chelate reductase, nitrate reductase, cyt b 5 reductase and peroxidase. The auxin stimulated oxidase has been proposed to be involved in control of cell elongation or proliferation and the iron chelate reductase in iron uptake. The peroxidase may be important in defense against pathogens