Due to climate change, sessile oak (Quercus petraea) seedlings experience an increasing risk of drought during regeneration of forest stands by management practices. The present study was aimed at elucidating the potential of sessile oak seedlings originating from sites with different aridity and nitrogen (N) supply to acclimate to contrasting water availability. For this purpose, a free-air cross-exchange experiment was conducted between a dry and a humid forest stand with high and low soil N contents, respectively during two consecutive years differing in aridity before harvest. Almost all structural and physiological foliar traits analyzed did not differ consistently between seed origins during both years, when cultivated at the same site. As an exception, the arid provenance upregulated foliar Ascorbate (Asc) contents under drought, whereas the humid provenance accumulated the phenolic antioxidants vescalagine and castalagine (VC) under favorable weather conditions and consumed VC upon drought. Apparently, differences in long-term aridity at the forest sites resulted in only few genetically fixed differences in foliar traits between the provenances. However, structural and physiological traits strongly responded to soil N contents and weather conditions before harvest. Foliar N contents and its partitioning were mostly determined by the differences in soil N availability at the sites, but still were modulated by weather conditions before harvest. In the first year, differences in aridity before harvest resulted in differences between most foliar traits. In the second year, when weather conditions at both sites were considerably similar and more arid compared to the first year, differences in foliar traits were almost negligible. This pattern was observed irrespective of seed origin. These results support the view that leaves of sessile oak seedlings generally possess a high plasticity to cope with extreme differences in aridity by immediate acclimation responses that are even better developed in plants of arid origin.

中文翻译：

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无梗栎（Quercus petraea Liebl）幼苗的叶片性状主要由部位特性而不是种子起源决定。

由于气候变化，无梗橡木（Quercus petraea根据管理规范，在林分再生期间，幼苗遭受干旱的风险增加。本研究旨在阐明源自干旱和氮素供应不同的无梗橡树幼苗适应水的可利用性的潜力。为此，分别在连续的两年中，在收获前的干旱不同的情况下，分别在土壤氮含量高和低的干燥和潮湿林分之间进行了自由空气交叉交换实验。在同一地点种植的两年中，几乎所有种子的结构和生理叶片性状在两年间都没有一致的差异。作为例外，干旱的种源在干旱下上调了抗坏血酸（Asc）的含量，潮湿的种源在有利的天气条件下积累了酚类抗氧化剂维斯卡林和卡他拉汀（VC），而在干旱时消耗了VC。显然，森林地带的长期干旱差异导致各种源之间叶片性状的遗传固定差异很小。但是，结构和生理性状对土壤氮含量和收获前的天气条件有强烈的响应。叶面氮含量及其分配主要取决于土壤氮素利用率的差异，但仍受收获前天气条件的调节。在第一年，收获前的干旱差异导致大多数叶片性状之间的差异。第二年 与第一年相比，当两个地点的天气条件非常相似且更加干旱时，叶片性状的差异几乎可以忽略不计。不论种子来源如何，都观察到这种模式。这些结果支持这样的观点，即无梗橡树幼苗的叶子通常具有很高的可塑性，可以通过即时适应性反应来应对干旱方面的极端差异，而干旱地区的植物甚至可以更好地发育这种即时适应性反应。