title: X-ray microanalytical studies of mineral elements in the tripartite symbiosis between lima bean, N2-fixing bacteria and mycorrhizal fungi.
abstract: The symbiosis between legumes, arbuscular mycorrhizal (AM) fungi, and N2-fixing bacteria (NFB) provides mutual nutritional gains. However, assessing the nutritional status of the microorganisms is a difficult task. A methodology that could assess this status, in situ, could assist managing these organisms in agriculture. This study used X-ray microanalyses to quantify and locate mineral elements in structures formed in a tripartite symbiosis. Lima bean (Phaseolus lunatus L. Walp) was cultivated in pots under greenhouse conditions, to which we have added AM fungal isolates (Glomus macrocarpum and Acaulospora colombiana) and NFB (Bradyrhizobium japonicum) inocula. Uninoculated control plants were also included. Symbionts were evaluated at the onset of flowering. Quantification of the mineral elements in the symbiotic components was performed using energy dispersive X-ray spectroscopy (EDX) and a scanning electron microscopy (SEM) was used to identify structures. EDX analysis detected 13 elements with the most abundant being N, Ca, and Se, occurring in all tissues, Fe in roots, Ni and Al in epidermis and P and Mo in nodules. Elemental quantification in fungal structures was not possible. The distribution of elements was related to their symbiotic function. X-ray microanalysis can be efficiently applied for nutritional diagnosis in tripartite symbiosis.
authors.affiliation: Department of Soil Science, Federal University of Lavras (UFLA), University Campus, 372000-000, Lavras, Minas Gerais, Brazil.
authors.forename: Bruna Wurr
authors.initials: BW
authors.lastname: Rodak
authors.affiliation: Department of Soil Science, Federal University of Lavras (UFLA), University Campus, 372000-000, Lavras, Minas Gerais, Brazil. Electronic address: doug20106@gmail.com.
authors.forename: Douglas Siqueira
authors.initials: DS
authors.lastname: Freitas
authors.affiliation: Department of Soil Science, Federal University of Lavras (UFLA), University Campus, 372000-000, Lavras, Minas Gerais, Brazil.
authors.forename: Soraya Marx
authors.initials: SM
authors.lastname: Bamberg
authors.affiliation: Department of Soil Science, Federal University of Lavras (UFLA), University Campus, 372000-000, Lavras, Minas Gerais, Brazil.
authors.forename: Marco Aurélio Carbone
authors.initials: MA
authors.lastname: Carneiro
authors.affiliation: Department of Soil Science, Federal University of Lavras (UFLA), University Campus, 372000-000, Lavras, Minas Gerais, Brazil.
authors.forename: Luiz Roberto Guimarães
authors.initials: LR
authors.lastname: Guilherme
mesh_terms: D004577:Electron Probe Microanalysis; D007887:Fabaceae / Q000737:chemistry / Q000382:microbiology*; D008855:Microscopy, Electron, Scanning; D038821:Mycorrhizae / Q000302:isolation & purification*; D000072738:Nitrogen-Fixing Bacteria / Q000302:isolation & purification*; D010316:Particle Size; D018517:Plant Roots / Q000737:chemistry / Q000382:microbiology; D013052:Spectrometry, X-Ray Emission; D013559:Symbiosis; D014131:Trace Elements / Q000032:analysis*
chemical_list: D014131:Trace Elements
keywords: Distribution; EDX mapping; Nutritional status; Phaseolus lunatus; Quantification; SEM micrographs