Alterations in the pattern of peroxidase isoenzymes and transient increases in its activity and in H2O2 levels take place during the dormancy cycle of grapevine buds: The effect of hydrogen cyanamide

Abstract

Polymorphism of peroxidase (Px) and changes in its activity and in H 2O2 content were studied in buds of grapevine during dormancy. Three isoforms of Px were detected in bud-extracts, two basic and one acidic, however, the pattern of Px isoenzyme changed with the progress of dormancy. Thus, basic Px isoenzymes disappeared from extracts previous to the onset of bud-break, while acidic isoenzymes remained relatively unaltered throughout the whole dormancy period. Furthermore, transient increases in the activity of Px and in the content of H2O2 occurred previous to endodormancy release, when buds were fully dormant. Hydrogen cyanamide (H2CN2), a potent bud breaking agent in grapevines advanced as expected budbreak, but also advanced the occurrence of Px and H2O2 peaks and the changes in Px isoenzymes pattern. The results suggests that H2O2 could function as a signalling molecule inducing endodormancy release, and changes in Px polymorphism could be a useful marker to study endo/ecodormanc