Abstract:

Peroxidases are known to play important roles in plant wound healing. Biochemical analysis and histochemical localization techniques were used to assess changes and distribution of peroxidases in the recovering bark after girdling in Eucommia ulmoides Oliv. Between 4 and 21 days after girdling (DAG), peroxidases activity in the girdled trees significantly increased by 30-40 times over that in ungirdled trees. During the whole bark recovery process (from 0 to 63 DAG), the peroxidase signal was not found in the tissue regions subjected to intense cell division activity (regenerating cambial zone and phellogen). However, high peroxidase activity was detected in the callus, cortex-like, mature phloem and xylem. Interestingly, it was shown that, in maturing xylem and phloem cells, there was respectively an inward and outward peroxidase activity gradient on both sides of the cambium zone. An isoelectric-focusing electrophoresis of the extracted protein displayed two isozyme bands of peroxidase: PODⅠand PODⅡ. PODⅠwas only detected in the xylem fraction and could play a role in xylem differentiation. PODⅡ was only identified in the recovering bark portion and could be more engaged in bark regeneration process. A relationship between IAA and peroxidase is also discussed.

Key words: peroxidase, cambium, Eucommia ulmoides, girdling, regeneration, isozyme