Abstract

Plants acquire multiple resources from the environment and may need to adjust and/or balance their respective resource-use efficiencies to maximize grow and survival, in a locally adaptive manner. In this study, tissue and whole-plant carbon (C) isotopic composition (δ¹³C) and carbon/nitrogen (C/N) ratios provided long-term measures of use efficiencies for water (WUE) and nitrogen (NUE), and a nitrogen (N) isotopic composition (δ¹⁵N)-based mass balance model was used to estimate traits related to N uptake and assimilation in heart-leaved willow (Salix eriocephala Michx.). In an initial common garden experiment consisting of 34 populations, we found population-level variation in δ¹³C, C/N ratio and δ¹⁵N, indicating different patterns in WUE, NUE and N uptake and assimilation. Although there was no relationship between foliar δ¹³C and C/N ratios among populations, there was a significant negative correlation between these measures across all individuals, implying a genetic and/or plastic trade-off between WUE and NUE not associated with local adaptation. To eliminate any environmental effect, we grew a subset of 21 genotypes hydroponically with nitrate as the sole N source and detected significant variation in δ¹³C, δ¹⁵N and C/N ratios. Variation in δ¹⁵N was mainly due to genotypic differences in the nitrate efflux/influx ratio (E/I) at the root. Both experiments suggested clinal variation in δ¹⁵N (and thus N uptake efficiency) with latitude of origin, which may relate to water availability and could contribute to global patterns in ecosystem δ¹⁵N. There was a tendency for genotypes with higher WUE to come from more water-replete sites with shorter and cooler growing seasons. We found that δ¹³C, C/N ratio and E/I were not inter-correlated, suggesting that the selection of growth, WUE, NUE and N uptake efficiency can occur without trade-off.

中文翻译：

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C和N同位素鉴别的基因型变异表明心叶柳的局部适应

摘要

植物从环境中获取多种资源，可能需要调整和/或平衡它们各自的资源利用效率，以适应当地情况，最大限度地提高生长和生存。在这项研究中，组织和整株植物的碳 (C) 同位素组成 (δ ¹³ C) 和碳/氮 (C/N) 比率提供了水 (WUE) 和氮 (NUE) 使用效率的长期衡量标准，以及使用基于氮 (N) 同位素组成 (δ ¹⁵ N) 的质量平衡模型来估计心叶柳 ( Salix eriocephala Michx.) 中与 N 吸收和同化相关的性状。^{在一个由 34 个种群组成的初始普通花园实验中，我们发现 δ 13} C、C/N 比和 δ ¹⁵的种群水平变化N，表示 WUE、NUE 和 N 吸收和同化的不同模式。尽管群体之间的叶面 δ ¹³ C 和 C/N 比率之间没有关系，但这些测量值在所有个体之间存在显着负相关，这意味着 WUE 和 NUE 之间的遗传和/或塑料权衡与局部适应无关. 为了消除任何环境影响，我们用硝酸盐作为唯一的 N 源水培培养了 21 种基因型的子集，并检测到 δ ¹³ C、δ ¹⁵ N 和 C/N 比率的显着变化。δ ¹⁵ N 的变化主要是由于硝酸盐流出/流入比（E / I） 在根。两项实验均表明 δ ¹⁵ N（以及因此 N 吸收效率）随起源纬度的临床变化，这可能与水的可用性有关，并可能有助于生态系统 δ ¹⁵ N 的全球模式。具有更高 WUE 的基因型趋向于出现来自生长季节较短和较冷的更多水充足的地点。我们发现 δ ¹³ C、C/N 比和E / I没有相互关联，这表明生长、WUE、NUE 和 N 吸收效率的选择可以在没有权衡的情况下发生。