Effect of Foliar Spray of Gibberellin on the Incidence of Internal Browing in Roots of Japanese Radish

Abstract

Effects of GA₃, uniconazole, and the their combination treatments on the incidence of internal root browning, polyphenol contents, and polyphenol oxidase activity in roots of Japanese radish were investigated.
1. Foliar sprays of 50 to 150 ppm GA₃ reduced the incidence of internal root browning; the most effective concentration was 100 ppm GA₃. Foliar sprays of 10 and 20 ppm uniconazole increased the incidence of internal root browning. Polyphenol contents and polyphenol oxidase activity in roots were decreased by GA₃ but increased by uniconazole.
2. The combined treatment of GA₃ applied to leaves and of super phosphate applied to the Ando soil decreased the incidence of internal root browning more effectively than did each as a single treatment. Polyphenol contents and polyphenol oxidase activity in roots were lower in a combined and single treatments than in untreated control.
These results suggest that the internal root browning of Japanese radish can be controlled by exogenous GA₃ and by super phosphate which lower the polyphenol contents and polyphenol oxidase activity in the roots.