Key message

Local adaptation largely segregates between traits affecting light responses and water relations, but population-level differences in stomatal conductance when growth is unconstrained converge among populations under water stress.

Abstract

Warming temperatures and altered precipitation patterns threaten plant populations worldwide. European beech (Fagus sylvatica) is a species that expresses both high phenotypic plasticity and local adaptation among populations. Beech seedlings’ susceptibility to prolonged drought may be dictated by their immediate light environment. We tested whether seedlings of four beech provenances, from contrasting edaphoclimatic environments, expressed differences in trait responses to imposed water stress under sun and shade treatments. Populations from the southern range margin were expected to display greater water-stress tolerance and core populations’ faster growth rates in the absence of abiotic limitations. Both high light and water stress induced differences in trait responses among provenances, but traits that failed to respond to our experimental treatments likewise did not segregate at the provenance level. Hence, those traits responding to light, e.g., increasing leaf flavonol index and leaf mass area, also tended to differ among provenances. Similarly, there was evidence of local adaptation among provenances in traits, like midday leaf water potential, responding to water stress. Exceptionally, there was a three way interaction water- × -light- × -provenance for stomatal conductance which converged among provenances under water stress. Leaf chlorophyll content also varied both with light and water in a provenance-specific manner. We found core provenances’ growth traits to outperform others under favourable conditions, whereas southern and high-elevation populations displayed traits adapted to tolerate high irradiance. Only stomatal conductance produced a complementary interactive response between light- × -water across provenances, whereas other traits responded less to combined water stress and high irradiance than to either treatment alone.

中文翻译：

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欧洲山毛榉边缘种群和核心种群的幼苗对干旱和阴凉的反应不同

关键信息

局部适应主要在影响光响应和水分关系的性状之间隔离，但是当水分不受限制地生长时，在水分胁迫下种群间气孔导度的种群水平差异会趋于一致。

抽象

气温升高和降水模式改变威胁着全世界的植物种群。欧洲榉木（水青冈）是一种既表现出高表型可塑性，又在种群之间局部适应的物种。山毛榉幼苗对长时间干旱的敏感性可能取决于它们的直接光照环境。我们测试了来自四个山毛榉种源的幼苗，是否来自相反的水生气候环境，在阳光和阴凉处理下对施加的水分胁迫的性状响应是否有所不同。在没有非生物限制的情况下，预计南部山脉边缘的种群将表现出更大的耐水压力，核心种群的生长速度更快。高强度光照和水分胁迫均会导致种源之间的性状响应差异，但是未能对我们的实验处理产生响应的性状在种源水平上也没有分离。因此，那些对光有反应的特征，例如 叶黄酮指数和叶质量面积的增加，在种源之间也趋于不同。同样，有证据表明，中部种源之间的局部适应对水分胁迫产生了响应，例如中午叶片水势。例外地，在水分胁迫下，气孔传导的水-×-光-×-三种交互作用方式在种源之间收敛。叶片的叶绿素含量也随光和水的不同而以出处特定的方式变化。我们发现，在有利条件下，核心种源的生长特性要优于其他种，而南部和高海拔种群显示出的特性适合于高辐照度。只有气孔电导产生了不同来源的轻水之间的互补相互作用，