Metabolic Changes in Sweet Potato Roots Induced by Gamma Radiation in Response to Cutting

Sweet potato roots were irradiated with 5 to 120 krads of cobalt-60 gamma rays, and then cut into disks, which were incubated under aerobic conditions. The effects of gamma radiation on metabolic changes in the tissue in response to cutting were investigated. The polyphenol content and activities of o-diphenol oxidase, peroxidase, and phenyalanine ammonialyase increased greatly in both nonirradiated and irradiated samples after cutting. Following irradiation with 60 krads or more the polyphenol content and peroxidase activity in response to cutting was significantly stimulated over the nonirradiated sample. On the contrary, formation of lignin-like substance was inhibited. No significant effect on o-diphenol oxidase was observed at any dose tested. In samples irradiated with 90 krads an increase in phenylalanine ammonia-lyase was correlated with the increase in polyphenol content.