The distribution of polyphenols, chlorogenic acid oxidase and peroxidase in different plant parts of tobacco, Nicotiana tabacum L

Abstract

Amounts of polyphenols, chlorogenic acid oxidase and peroxidase activities and isozymes in the plant parts of greenhouse-grown burley and flue-cured tobaccos, Nicotiana tabacum, have been compared. On a dry weight basis, flower parts, especially the pistil, are about 150-fold higher in phenolic content than the seed and three to five times greater than the leaf. Leaf laminae, either young or senescent, contain more polyphenols than stem, leaf midrib, pith, and root. Three geometric isomers of chlorogenic acid exist in all green tissues as well as in flower parts but only two are detected in the root. The latter contains a high proportion of scopolin and scopoletin, both of which are in low concentrations in photosynthetic tissues and completely absent in pistil. By means of ammonium sulfate fractionation, chlorogenic acid oxidase and peroxidase have been separated from the same tissue extracts. Seeds have no detectable oxidase activity. The activity of chlorogenic acid oxidase is highest in root, lower in pistil, corolla, and stem, and lowest in anther, leaf, and pith. Young leaves exhibit seven times more activity than senescent ones. On the contrary, the leaf peroxidases increase in concentration from upper to bottom stalk positions. Peroxidase content is highest in root but lowest in flower parts. Polyacrylamide gel block electrophoresis has revealed two cathodic and ten anodic isoperoxidases in the leaves varying in physiological age. Two anodic and two cathodic isoperoxidases in slow mobility are lacking in pith and reproductive organs but appear as intensive bands in root. Zymograms of chlorogenic acid oxidase are identical to that of isoperoxidase for all plant parts except pistil and corolla, which have a cathodic band migrating father away from the origin. Results suggest that the distribution patterns of polyphenols and two oxidases in the plant parts of two tobacco strains coincide with each other, and within a plant the correlation between phenolic quantity and oxidase activity varies depending upon the organs and tissues.