Embothrium coccineum is a pioneer tree that produces cluster roots (CR) induced by phosphorus (P) or nitrogen (N) deficiency, but the role which both N and P play in CR formation for different E. coccineum populations is still unknown. We hypothesized that in E. coccineum, N influences the CR formation response, primarily induced by P limitation. However, this response depends on local adaptations to their specific conditions of geographic origin. Seedlings from three contrasting edaphoclimatic conditions (Northern, Central and Southern populations) were grown in hydroponic culture under high and low N supply and at five different P supply. Morphophysiological responses, including CR number, growth, biomass, P and N plant concentration, were studied. Our results showed that at high N supply, CR formation was stimulated with increased P supply, but just until it reaches a maximum of 5 μM, above this concentration CR formation decreases. However, at low N supply, a constitutive response was observed regardless of P supply. Moreover, each of these responses depends on the populations. Our study suggests that N drives CR formation induced by P supply and that a differential response exists among E. coccineum populations, that could be related to their origin edaphoclimatic conditions.

中文翻译：

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不同地理来源的 Embothrium coccineum 种群中磷和氮供应诱导簇根形成的对比反应

Embothrium coccineum 是一种由磷（P）或氮（N）缺乏诱导产生簇根（CR）的先锋树，但 N 和 P 在不同 E. coccineum 种群的 CR 形成中的作用仍然未知。我们假设在 E. coccineum 中，N 影响 CR 形成响应，主要由 P 限制引起。然而，这种反应取决于当地对其地理起源的特定条件的适应。来自三种不同土壤环境条件（北部、中部和南部种群）的幼苗在高和低氮供应和五种不同的磷供应下在水培培养中生长。研究了形态生理反应，包括 CR 数、生长、生物量、P 和 N 植物浓度。我们的结果表明，在高氮供应下，增加磷供应刺激了 CR 的形成，但直到达到最大 5 μM，高于此浓度，CR 形成才会减少。然而，在低氮供应下，无论磷供应如何，都观察到本构响应。此外，这些反应中的每一个都取决于人群。我们的研究表明 N 驱动由 P 供应诱导的 CR 形成，并且 E. coccineum 种群之间存在差异反应，这可能与其起源的土壤气候条件有关。