Aims

The relationships between nitrogen (N) and phosphorus (P) acquisition strategies among herbaceous legume species remain poorly understood, particularly in relation to how they are altered by N availability. This study aimed to investigate the relationships between N₂ fixation, plant N concentration and P acquisition through two main strategies in temperate herbaceous legumes, and to demonstrate the influences of soil N availability on these relationships.

Methods

In a field pot experiment, eight temperate herbaceous legumes were grown with or without N addition. Plant growth, plant N and P concentrations, N₂ fixation, arbuscular mycorrhizal (AM) fungal colonization and root phosphatase activity (RPA) were measured, and the relationships between N₂ fixation, plant N concentration and each P acquisition strategy were assessed under contrasting N availability.

Results

N addition increased RPA. However, AM fungal colonization showed species-specific responses to N addition, and the ratio of AM fungal colonization to root phosphatase activity was decreased by N addition. Among eight legume species, AM fungal colonization increased with N₂ fixation rate in the absence of N addition, but no relationship was observed with N addition. RPA increased with plant N concentration among legume species, regardless of N addition.

Conclusions

As two key P acquisition strategies, neither RPA nor AM fungal colonization of temperate herbaceous legumes were species-specific traits, since both were positively correlated with N₂ fixation rate and plant N concentration. In addition, the correlation between N₂ fixation and AM fungal colonization was regulated by N availability. While N enrichment intensifies the legume reliance on RPA for acquiring more P, it weakens the association of N₂ fixation in driving across species AM colonization.

中文翻译：

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富氮强化了豆科植物对根磷酸酶活性的依赖，但削弱了 N2 固定与菌根定植之间的种间相关性

宗旨

草本豆科植物中氮 (N) 和磷 (P) 获取策略之间的关系仍然知之甚少，尤其是关于它们如何被 N 可用性改变的关系。本研究旨在通过温带草本豆科植物的两种主要策略研究 N ₂固定、植物 N 浓度和 P 获取之间的关系，并证明土壤 N 可用性对这些关系的影响。

方法

在田间盆栽试验中，在添加或不添加氮的情况下种植了八种温带草本豆科植物。测量植物生长、植物 N 和 P 浓度、N ₂固定、丛枝菌根 (AM) 真菌定植和根磷酸酶活性 (RPA)，并在对比下评估N ₂固定、植物 N 浓度和每种 P 获取策略之间的关系N 可用性。

结果

N另外增加了RPA。然而，AM 真菌定植对 N 添加显示出物种特异性反应，并且 AM 真菌定植与根磷酸酶活性的比率因 N 添加而降低。在八种豆科植物中，在不添加氮的情况下，AM 真菌定植随 N ₂固定率增加，但与添加 N 没有关系。RPA 随着豆科植物中植物 N 浓度的增加而增加，而与 N 添加无关。

结论

作为两个关键的磷获取策略，温带草本豆科植物的 RPA 和 AM 真菌定植都不是物种特异性性状，因为两者都与 N ₂固定率和植物 N 浓度呈正相关。此外，N ₂固定和AM真菌定植之间的相关性受N可用性调节。虽然 N 富集加强了豆科植物对 RPA 获取更多 P 的依赖，但它削弱了 N ₂固定在驱动跨物种 AM 定植中的关联。