Cherry Fruit Growth: Localization of Indoleacetic Acid Oxidase and Inhibitors in the Seed

Abstract

Abstract The distribution of indoleacetic acid (IAA) oxidase activity was determined in seeds of sour cherry (Prunus cerasus L. cv. Montmorency) fruits in mid-Stage II of development, 32 days after full bloom. The greatest activity was found in the integument tissue. No IAA oxidase activity was detected in the embryo or endosperm. When polyvinylpolypyrrolidone (PVP) was added to the extraction buffer (0.2 m acetate, pH 4.0), a trace of activity was detected in the embryo, but not in the endosperm. Inhibitors of IAA oxidase were coextracted with the enzyme and occurred in the greatest quantity in the integument tissue, an intermediate level in the embryo, and only a trace in the endosperm. The inhibitor from the integument and embryo tissues exhibited different kinetics when increasing concentrations were assayed against IAA oxidase isolated from the integuments. The possible significance of IAA oxidase and inhibitor distribution in the seed is discussed in relation to sour cherry fruit growth.