The Effects of Phenolic Compounds on Peroxidase and Polyphenol Oxidase in Dwarf Pea (Pisum sativum var. «Little Marvel») Tissue

Abstract

Summary Ethrel (3 ppm) and ultraviolet irradiation (UV), separate and in combination with visible or dark, were applied to seeds of dwarf pea ( Pisum sativum , var. «Little Marvel») to determine their effect in the presence of sixteen different substrates, on polyphenol oxidase and peroxidase activity in 20 day-old distal root, root tip, leaf, and proximal stem tissues respectively. In terms of polyphenol oxidase activity, the enzyme is light dependent and activity is highest in visible light-exposed tissue, followed by UV plus Ethrel-treated tissues in comparison to untreated controls. Distal root and root tip tissues generally contained higher PPO activity than did the leaf or proximal stem tissues. Hydroxyanthranilic acid, catechol, and pyrogallol appear to be the most reactive substrates for PPO activity. Ethrel caused an increase in peroxidase activity in root tip and proximal stem tissues and depressed enzymic activity in distal root tissue. Leaf tissue had the highest level of peroxidase activity and etiolated tissue demonstrated higher levels of peroxidase activity than did visible lighttreated tissue. In addition to showing high specificity with the three aforementioned substrates that were cited as being specific for PPO, peroxidase activity was also specific with guaiacol and p-phenylene diamine.