Do olive vegetative buds undergo a real dormant state in winter?

Abstract

Understanding the mechanisms regulating vegetative and reproductive growth is important for modelling purposes, as the partitioning of carbohydrates is dependent on phenology. In olive trees, floral buds undergo a winter endodormant state that is released once they have been exposed to long enough periods of chilling temperatures. Similarly, the apical vegetative buds stop their activity during winter, but it is unknown so far whether growth cessation is triggered by endodormancy or by unfavourable low temperature conditions (ecodormancy). The aim of the present work was to shed some light on this issue. To this end, an experiment was carried out in Córdoba (Spain) with young potted 'Arbequina' olive trees. Plants were grouped in sets of three individuals that were transferred to a greenhouse with an optimal temperature for growth at different dates over the course of a winter (from late November to early March). The activity of vegetative buds was assessed weekly by counting the number of new leaf pairs generated on market shoots. In all cases, apical buds resumed their activity fairly soon after their entry into the greenhouse (‹2-3 weeks), but both the time for bud brake and rate of new leaf appearance was influenced by the date of entry. In particular, bud break took longer and subsequent growth rates were lower for the plants transferred into the greenhouse in early winter than for those plants moved to the greenhouse on later dates. It is concluded that olive apical buds undergo an easily-reversible endodormant state in winter.