Gil Quintana, ErenaLarrainzar Rodríguez, EstíbalizArrese-Igor Sánchez, CésarGonzález García, Esther2017-04-112017-04-1120130022-0957 (Print)1460-2431 (Electronic)10.1093/jxb/ers334https://academica-e.unavarra.es/handle/2454/24090Drought stress is a major factor limiting nitrogen fixation (NF) in crop production. However, the regulatory mechanism involved and the origin of the inhibition, whether local or systemic, is still controversial and so far scarcely studied in temperate forage legumes. Medicago truncatula plants were symbiotically grown with a split-root system and exposed to gradual water deprivation. Physiological parameters, NF activity, and amino acid content were measured. The partial drought treatment inhibited NF in the nodules directly exposed to drought stress. Concomitantly, in the droughted below-ground organs, amino acids accumulated prior to any drop in evapotranspiration (ET). It is concluded that drought exerts a local inhibition of NF and drives an overall accumulation of amino acids in diverse plant organs which is independent of the decrease in ET. The general increase in the majority of single amino acids in the whole plant questions the commonly accepted concept of a single amino acid acting as an N-feedback signal.application/pdfeng© 2012 The Author(s). This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly citedAmino acidsDroughtLocal regulationMedicago truncatulaN-feedback inhibitionNitrogen fixationTranspirationinfo:eu-repo/semantics/articleinfo:eu-repo/semantics/openAccess