INRA, UMRA 547 PIAF, site INRA de Crouelle, 234 avenue du Brézet, 63100 Clermont-Ferrand Cedex 02, France.
Tree Physiol. 2010 Dec;30(12):1555-69. doi: 10.1093/treephys/tpq087. Epub 2010 Oct 28.
It has been hypothesized that the increase in temperature in this century could lead to an increase in frost damage to plant tissues. Several models have been proposed to describe the development of cold hardiness, but never taking into account extreme climatic and/or physiological events. Our results on walnut tree (Juglans regia L.) show that cold hardiness was best correlated with average daily temperatures minimal temperatures over the last 15 days before sampling (T(min 15 days)), indicating that the freezing tolerance depended on the tree's climatic history. Moreover, this study also shows that the accumulation of sucrose and the water content (WC) decrease are an essential step towards cold hardiness. Thus, a simple linear model based on climatic (T(min 15 days)) and physiological (soluble sugars, WC) explanatory variables was developed to predict the cold hardiness level in walnut stem at any time during the leafless period. Each of the three input variables can be assigned a specific role contributing to the simulated function, cold hardiness. The extent and robustness of this relation was assessed on extreme physiological events on walnut trees bearing three main branches. On each tree, one branch was defoliated to limit the local carbohydrate and transpiration, one was girdled to increase local carbohydrate and prevent carbohydrate export and the third one was kept untreated as control. As expected, these treatments impacted both local carbon reserves and WC in the stems born by each main branch in comparison with the control on the same tree. The impact of these treatments on stem's freezing tolerance, as evaluated by an electrolyte leakage method (LT₅₀), confirmed the direct impact of soluble sugar and WC on cold hardiness over a wide range of carbohydrate and WC. This is discussed in relation to the branch autonomy theory for carbon but also for water during summer growth and winter periods. The present study demonstrates the importance of physiological parameters in the prediction of cold hardiness and proposes a way to model cold hardiness with extreme climatic and/or physiological events.
有人假设，本世纪温度的升高可能导致植物组织的霜害增加。已经提出了几种模型来描述抗寒性的发展，但从未考虑过极端的气候和/或生理事件。我们对核桃树（Juglans regia L.）的研究结果表明，抗寒性与采样前 15 天的平均日温和最低温度（T(min 15 天)）密切相关，这表明抗冻性取决于树木的气候历史。此外，这项研究还表明，蔗糖的积累和含水量（WC）的降低是抗寒性形成的关键步骤。因此，开发了一个基于气候（T(min 15 天））和生理（可溶性糖、WC）解释变量的简单线性模型，以预测无叶期内任何时间核桃树干的抗寒性水平。三个输入变量中的每一个都可以分配一个特定的角色，为模拟函数（抗寒性）做出贡献。在核桃树上进行了三个主要分枝的极端生理事件的评估中，评估了这种关系的程度和稳健性。在每棵树上，一个分枝被去除以限制局部碳水化合物和蒸腾作用，一个分枝被环割以增加局部碳水化合物并防止碳水化合物输出，第三个分枝保持未处理作为对照。正如预期的那样，与同一树上的对照相比，这些处理对每个主分枝产生的茎中局部碳储量和 WC 都有影响。用电解质泄漏法（LT₅₀）评估这些处理对茎的抗冻性的影响，证实了可溶性糖和 WC 对广泛的碳水化合物和 WC 范围内抗寒性的直接影响。这与夏季生长和冬季期间碳的分枝自主性理论以及水的分枝自主性理论有关。本研究证明了生理参数在预测抗寒性中的重要性，并提出了一种利用极端气候和/或生理事件来建模抗寒性的方法。
