University of Bonn, Horticultural Sciences, Institute of Crop Science and Resource Conservation (INRES), Auf dem Hügel 6, 53121, Bonn, Germany.
University of Hohenheim, Institute of Crop Science, Section Production Systems of Specialty Crops (340f), Emil-Wolff-Street 25, 70599 Stuttgart, Germany.
Tree Physiol. 2024 Oct 3;44(10). doi: 10.1093/treephys/tpae112.
Dormancy in temperate fruit trees is a mechanism of temporary growth suspension, which is vital for tree survival during winter. Studies on this phenomenon frequently employ scientific methods that aim to detect the timing of dormancy release. Dormancy release occurs when trees have been exposed to sufficient chill, allowing them to resume growth under conducive conditions. This study investigates dormancy dynamics in two apple (Malus × domestica Borkh.) cultivars, 'Nicoter' and 'Topaz', by sampling branches in an orchard over 14 weeks (2019 to 2020) and over 31 weeks (2021 to 2022) and subjecting them to a 42-day budbreak forcing period in a growth chamber. Temporal changes in budbreak percentages demonstrated dormancy progression in the studied apple cultivars and allowed the three main dormancy phases to be distinguished: paradormancy (summer dormancy), endodormancy (deep dormancy) and ecodormancy (spring dormancy), along with transition periods between them. Using these data, we explored the suitability of several alternative methods to determine endodormancy release. Tabuenca's test, which predicts dormancy release based on the differences in dry weights of buds with and without forcing, showed promise for this purpose. However, our data indicated a need for considerable adjustments and validation of this test. Bud weight and water content of buds in the orchard did not align with budbreak percentages under forcing conditions, rendering them unsuitable for determining endodormancy release in 'Nicoter' and 'Topaz'. Shoot growth cessation did not seem to be connected with either dormancy progression or dormancy depth of the studied cultivars, whereas leaf fall coincided with the beginning of the transition from endo- to ecodormancy. This work addresses methodological limitations in dormancy research and suggests considering the mean time to budbreak and budbreak synchrony as additional criteria to assess tree dormancy status.
休眠是温带果树暂时停止生长的机制，对于树木在冬季的生存至关重要。研究这一现象常采用科学方法来检测休眠的释放时间。当树木经历了足够的低温后，休眠就会被解除，从而在适宜的条件下恢复生长。本研究通过在果园中对两个苹果品种（Malus × domestica Borkh.）'Nicoter'和'Topaz'的枝条进行采样，历时 14 周（2019 年至 2020 年）和 31 周（2021 年至 2022 年），并在生长室中将其置于为期 42 天的萌芽强迫期，来研究休眠动态。萌芽百分比的时间变化表明研究苹果品种的休眠进程，并允许区分三个主要休眠阶段：前期休眠（夏季休眠）、终期休眠（深度休眠）和后期休眠（春季休眠），以及它们之间的过渡阶段。利用这些数据，我们探讨了几种替代方法来确定终期休眠释放的适用性。Tabuenca 测试，该测试根据有和无强迫的芽的干重差异来预测休眠释放，显示出对此目的的适用性。然而，我们的数据表明需要对该测试进行大量调整和验证。在果园中，芽的重量和含水量与强制条件下的萌芽百分比不一致，因此不适合用于确定'Nicoter'和'Topaz'的终期休眠释放。新梢生长停止似乎与研究品种的休眠进展或休眠深度无关，而叶片脱落与终期休眠向后期休眠的过渡开始同时发生。这项工作解决了休眠研究中的方法学限制，并建议考虑萌芽的平均时间和萌芽同步性作为评估树木休眠状态的附加标准。
