During the early stages of root induction in hypocotyls of mung bean cuttings, four new peroxidase isoenzymes are formed in that part of the cutting that produces roots. These isoenzymes are in addition to and different from the three already present in the hypocotyl. Forty-eight hr is required for the change to take place from the original three to seven isoenzymes. The change in isoenzyme pattern and root initiation itself are retarded when streptomycin is applied during the very early stages of root induction. However, during the latter part of the first 24-hr period after the cutting is made and when some of the new isoenzymes have already been formed, the rooting process becomes insensitive to this antibiotic. Cytologically, the occurrence of cell division is paralleled by the formation of the four new peroxidase isoenzymes. The delay in the occurrence of cell division caused by the presence of streptomycin is paralleled by a similar delay in the formation of the four new isoenzymes.
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