| Abstrakt: |
A total of 21 esterase, 3 acid phosphatase and 2 leucine aminopeptidase isoenzymes, in addition to peroxidases and catalases, were demonstrated in onion seedlings by starch-gel electrophoresis. In seedlings two weeks old, the root tip and the differentiated zone show very little enzymatic activity, whereas the secondary roots, hypocotyl and cotyledon are enzymatically very active. These differences are correlated with the intensity of cell division. Some esterase isoenzymes are apparently restricted to root, others to shoot tissues. At pH 8.1, anodically moving peroxidases are totally absent from shoot tissues. A developmental study of esterase isoenzyme patterns indicated that no great differences exist between primary root tips from roots 6-18 mm long and seeds germinated for three days, whereas a sudden decrease in enzymatic activity occurs in root tips after seven days' germination when the roots are about 25 mm long. This coincides with the decrease in mitotic frequency. Actinomycin D and gamma irradiation decreased mitotic frequency almost to zero hut did not significantly affect the esterase isoenzyme pattern in root tips. This shows that the activity of these isoenzymes, at least, is not necessarily dependent on cell division hut may well he a prerequisite for it. [ABSTRACT FROM AUTHOR] |
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