The emergent aquatic plant, Sagittaria cuneata, is an easily-identified and commonly-found species in the Great Plains region of North America and has the potential to be a bioindicator of nitrogen (N) and phosphorus (P) because of its previously-identified leaf plasticity in response to nutrient conditions. To identify associations between leaf morphology and soil and water nutrients, we conducted: (1) a 10-week controlled experiment in which plants were grown in nutrient-enriched sediment, nutrient-enriched water, or unamended control trials, and (2) a field study where emergent leaves were collected from 15 streams of varying nutrient concentrations. Plants grown in experimentally enriched sediment were more productive than those grown in enriched water or control conditions: they produced more emergent leaves and tubers, had a larger final biomass and height, and developed emergent leaves that showed a consistent increase in size and unique change in shape over time. Emergent leaves collected from field plants also showed significant variability of leaf traits; however, this variability occurred at all scales of replication (leaf, plant, quadrat, and site), with linear mixed effects modelling indicating that random chance was likely driving this variability. Although sediment nutrients were crucial to successful growth of S. cuneata under controlled conditions, the high variability in leaf morphology under field conditions (likely due to large natural variability at the species, population, and individual scale) make leaf plasticity of S. cuneata unsuitable as a bioindicator. Our results emphasize the need to quantify within and among plant variation in leaf morphology (and to clarify sampling methods) for the many taxa of aquatic macrophytes that are phenotypically plastic and notoriously difficult to classify.

中文翻译：

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箭头（Sagittaria cuneata）作为草原溪流和湿地氮和磷的生物指示剂。

挺水水生植物慈姑 ( Sagittaria cuneata)是北美大平原地区一种易于识别且常见的物种，由于其先前已被识别，因此有可能成为氮 (N) 和磷 (P) 的生物指示剂。叶子对营养条件的可塑性。为了确定叶子形态与土壤和水养分之间的关​​联，我们进行了：(1) 为期 10 周的对照实验，其中植物在营养丰富的沉积物、营养丰富的水中生长，或未经修改的对照试验，以及 (2)现场研究，从 15 条养分浓度不同的溪流中收集了萌发的叶子。在实验富集沉积物中生长的植物比在富集水或对照条件下生长的植物生产力更高：它们产生更多的挺水叶和块茎，具有更大的最终生物量和高度，并且发育出的挺水叶表现出尺寸的持续增加和独特的变化。随着时间的推移而形成。从田间植物收集的挺水叶子也显示出叶子性状的显着变异；然而，这种变异性发生在所有复制规模（叶子、植物、样方和地点），线性混合效应模型表明随机机会可能驱动这种变异性。尽管沉积物养分对于S. cuneata在受控条件下的成功生长至关重要，但田间条件下叶片形态的高度变异性（可能是由于物种、种群和个体规模的巨大自然变异）使得 S. cuneata 的叶片可塑性不适合作为生物指示剂。我们的结果强调需要对许多表型可塑且极难分类的水生大型植物类群的叶子形态变化进行量化（并澄清采样方法）。