Background

The highly diversified flora in the Brazilian Cerrado (savanna) region is attributed to several factors, including the high concentrations of metals in soils, especially Al in widespread Ferralsols and Ni in soils derived from ultramafic rocks. We hypothesized that adaptation mechanisms are responsible for the genetic diversity of the following native plant species that are found in the abovementioned environments: Euploca salicoides (ES), Justicia lanstyakii (JL), and Oxalis hirsutissima (OH).

Objectives

We aimed to analyse the main edaphic factors that differentiate ultramafic from Al-rich environments, and act as drivers of the evolution of physiological mechanisms underlying plant adaptation to these harsh environments.

Methods

We analysed the chemical attributes of four ultramafic soils (SAP5, SAP7, SAP9, LAT) and an Al-rich soil (CAM), and the elemental composition and DNA of the three species growing in both environments. ES was used as a model species to analyse changes in the levels of non-structural carbohydrates (NSCs) and Ni localization in plant leaves.

Results

The soil types presented significant differences in available nutrients and heavy metals. The DNA sampled from the same species from ultramafic sites was genetically closer, but different from that in the Al-rich sites. In ultramafic soils, ES accessions had high levels of NSCs and Ni accumulated in trichomes.

Conclusions

The genetic diversity observed in plants growing in both areas is probably related to plant adaptation to the contrasting edaphic conditions of these environments. The raffinose production and Ni allocation to trichomes are mechanisms employed by ES to overcome metal toxification in ultramafic environments.

中文翻译：

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土壤因子作为巴西热带稀树草原恶劣环境中本土植物物种的遗传选择因子和适应驱动因子

背景

巴西塞拉多（稀树草原）地区高度多样化的植物群归因于几个因素，包括土壤中金属的高浓度，尤其是广泛分布的铁质溶胶中的铝和源自超镁铁质岩石的土壤中的镍。我们假设适应机制是导致在上述环境中发现的以下本地植物物种的遗传多样性的原因：Euploca salicoides (ES )、Justicia lanstyakii (JL) 和Oxalis hirsutissima (OH)。

目标

我们旨在分析区分超镁铁质与富铝环境的主要土壤因素，并作为植物适应这些恶劣环境的生理机制进化的驱动力。

方法

我们分析了四种超镁铁质土壤（SAP5、SAP7、SAP9、LAT）和富含铝的土壤（CAM）的化学属性，以及在这两种环境中生长的三种物种的元素组成和 DNA。ES被用作模型物种来分析植物叶片中非结构性碳水化合物（NSCs）和Ni定位水平的变化。

结果

土壤类型在有效养分和重金属方面存在显着差异。从超镁铁矿地点采集的同一物种的 DNA 在遗传上更接近，但与富含铝的地点的 DNA 不同。在超镁铁质土壤中，ES 种质在毛状体中积累了高水平的 NSC 和 Ni。

结论

在这两个地区生长的植物中观察到的遗传多样性可能与植物对这些环境的对比土壤条件的适应有关。棉子糖的产生和 Ni 分配给毛状体是 ES 用于克服超镁铁质环境中金属中毒的机制。