| Abstract: | The activities of polyphenol oxidase and peroxidase per unitarea of attached tobacco leaves increased as the leaves expanded,and reached a stable level in the mature leaves. After the onsetof senescence the enzyme activities fell rapidly, but at a laterstage they showed a small rise. Enzyme activities in tissuestaken from non-senescent leaves increased during incubationat 20 °C. These increases were sensitive to inhibitors ofprotein synthesis. Enzyme activities in tissues taken from leavesin early senescence increased during incubation at 35 °Cbut not at 20 °C. These increases were very largely insensitiveto inhibitors of protein synthesis and were not apparently relatedto de novo protein synthesis. There were no increases in enzymeactivities in tissues taken from leaves in late senescence andincubated at 35 °C or 20 °C. |
