Grapevine axillary meristems coordinate inner energy depletion and vascular tissue synthesis during budbreak

Bud dormancy in woody perennials is a complex physiological process regulated by seasonal environmental fluctuations. Both water status and energy reserve molecules are involved in the process of bud dormancy release, although their pre­cise roles remain a subject of ongoing debate. This study aimed to investigate the role of energy reserve molecules and the formation of vascular tissue in the grapevine during and after budbreak. Histochemical, microscopy, and biochemical techniques were employed to monitor the pattern of vascular tissue formation in the bud meristem and surrounding cane tissues, as well as the utilisation of reserve molecules, such as starch. Our findings revealed that starch reserves were rapidly consumed, a process associated with increased alpha-amylase activity. Furthermore, we observed the formation of new vascular tissues starting from the onset of budbreak until stage EL7, at which point functional connections between the emerging shoot and cane were established, ensuring the initiation of water transport.