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Organic N compounds in plant nutrition: have methodologies based on stable isotopes provided unequivocal evidence of direct N uptake?
Isotopes in Environmental and Health Studies ( IF 1.3 ) Pub Date : 2021-06-01 , DOI: 10.1080/10256016.2021.1932871
Christopher J Smith 1 , Phillip M Chalk 2
Affiliation  

ABSTRACT

During the past two decades, interest has developed in regard to the possibility that plant roots can take up organic N compounds directly, a concept which challenges the conventional wisdom that soil inorganic N forms (NH4+ and NO3) are the sole primary sources of N absorbed by plant roots. We reviewed the literature based on single or dual (15N, 13C) stable isotope labelling techniques to test the hypothesis of direct uptake. Both isotopically enriched and natural abundance approaches were reviewed. Of the methods examined, the dual enrichment technique, when combined with compound specific and position-specific stable isotope analysis, provided incontrovertible evidence for direct uptake of simple amino acids. We demonstrate that dual labelling lacks overall sensitivity due to the high C concentration in plant tissue relative to N, and the higher natural abundance of 13C cf. 15N, which limits the period of measurement due to isotope dilution, and hence an assessment of the long-term contribution of direct uptake to the N economy of plant communities.



中文翻译:

植物营养中的有机氮化合物:基于稳定同位素的方法是否提供了直接吸收氮的明确证据?

摘要

在过去的二十年中,人们对植物根系可以直接吸收有机氮化合物的可能性产生了兴趣,这一概念挑战了土壤无机氮形成的传统观点。NH4+3-) 是植物根系吸收氮的唯一主要来源。我们回顾了基于单或双(15 N,13 C)稳定同位素标记技术的文献,以测试直接吸收的假设。回顾了同位素富集方法和自然丰度方法。在检查的方法中,双重富集技术与化合物特异性和位置特异性稳定同位素分析相结合,为直接摄取简单氨基酸提供了无可争议的证据。我们证明,由于植物组织中相对于 N 的 C 浓度较高,以及13 C cf的较高天然丰度,双重标记缺乏整体敏感性。15N,由于同位素稀释而限制了测量周期,因此可以评估直接吸收对植物群落 N 经济的长期贡献。

更新日期:2021-07-20
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