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Mapeamento de QTLs para caracteres relacionados com a fixação biológica de nitrogênio (FBN) em soja; Mapping QTLs for traits associated with biological nitrogen fixation (BNF) in soybeans

Santos, Maria Aparecida dos
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 26/01/2010 PT
Relevância na Pesquisa
66.38%
A soja, [Glycine max (L.) Merrill] é uma das espécies com maior teor protéico, contendo cerca de 40% de proteína nos grãos. Em conseqüência disso demanda alta quantidade de nitrogênio (N), o qual pode ser suprido pelo processo de fixação biológica de nitrogênio (FBN), através da simbiose com as bactérias do gênero Bradyrhizobium. No Brasil, a FBN é capaz de suprir toda a demanda de N da cultura da soja, dispensando a aplicação de fertilizantes nitrogenados. No entanto, os caracteres relacionados à FBN não têm sido diretamente considerados em programas de melhoramento genético, em função das dificuldades inerentes às avaliações dos mesmos, que requerem a destruição das plantas. O objetivo deste trabalho foi mapear os locos de caracteres quantitativos (Quantitative Trait Loci: QTLs) dos caracteres relacionados à FBN, visando identificar associações úteis para a seleção assistida por marcadores, bem como obter outras informações sobre a base genética destes caracteres em soja. Uma população composta de 157 F2:7 linhagens endogâmicas recombinantes (Recombinant Inbred Lines RILs), derivada de um cruzamento biparental, foi genotipada com 105 marcadores microssatélites, bem como avaliada para os seguintes caracteres relacionados com a FBN: número de nódulos (NN); peso seco dos nódulos (MNS); peso médio dos nódulos secos (MNS/NN) e peso seco da parte aérea (MPAS). Utilizando o método de mapeamento por intervalo composto para múltiplas características (mCIM) foram mapeados os QTLs para os quatro caracteres. Um mapa genético foi construído com um tamanho estimado em 1.263...

Eficiência de uso de fósforo por cultivares de arroz e de feijoeiro e da fixação biológica de nitrogênio por cultivares de feijoeiro; Phosphorus use efficiency by rice and common bean cultivars and biological nitrogen fixation efficiency by common bean cultivars

Franzini, Vinicius Ide
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 09/09/2010 PT
Relevância na Pesquisa
66.35%
O fósforo (P) é considerado um dos principais nutrientes que limitam a produtividade do arroz de terras altas e do feijoeiro comum no Brasil, principalmente em muitos solos da região do Cerrado. A seleção de genótipos mais eficientes no uso de P é alternativa para a redução de gastos com adubação fosfatada e cultivo em solos mais pobres em P. O nitrogênio (N) é o nutriente absorvido em quantidades mais elevadas pelo feijoeiro comum. A seleção de genótipos mais eficientes na fixação biológica de N2 (FBN) é alternativa para reduzir os gastos com fertilizantes nitrogenados. O presente trabalho constou de três experimentos realizados em casa-de-vegetação do Laboratório de Fertilidade do Solo, Centro de Energia Nuclear na Agricultura - Universidade de São Paulo (CENA/USP). Em dois estudos foram cultivadas plantas de 47 genótipos de arroz de terras altas e 50 de feijoeiro comum em amostras de Latossolo Vermelho Amarelo distrófico típico, utilizando-se a técnica com o isótopo 32P para identificar os cultivares de arroz de terras altas e de feijoeiro comum mais eficientes quanto ao uso de P, descontando-se o P proveniente das sementes, e verificar se os mais eficientes ou com maior acúmulo de P na planta apresentam menores concentrações de cobre (Cu)...

Diversidade de bactérias diazotróficas e fixação biológica do nitrogênio na Mata Atlântica; Diversity of diazotrophic bacteria and biological nitrogen fixation in Brazilian Atlantic Rainforest

Gómez, Sandra Patricia Montenegro
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 25/07/2012 PT
Relevância na Pesquisa
66.35%
O presente trabalho estudou as relações entre as taxas de fixação biológica de nitrogênio (FBN), a composição e a diversidade da comunidade de bactérias diazotróficas de vida livre em três compartimentos: solo sob a copa, filosfera e dermosfera de diferentes espécies arbóreas, sendo que dermosfera foi avaliada em apenas duas espécies. As plantas escolhidas foram Euterpe edulis (Palmito juçara) Guapira opposita (Louro-branco) e Merostachys neesii (Bambu) presentes na Floresta Ombrófila Densa (FOD) de terras baixas e montanas do Parque Estadual da Serra do Mar, no Estado de São Paulo Brasil. As taxas de FBN foram estimadas pela técnica de redução de acetileno (ARA) através da relação teórica 3:1, baseada na redução de três moles de acetileno para cada mol de N fixado, e a composição da comunidade bacteriana foi acessada pelo sequenciamento parcial do gene rRNA 16S usando pirossequenciador. Foram encontradas diferenças nas estimativas das taxas de FBN que variaram entre as espécies arbóreas e principalmente entre os substratos. Os testes de comparação de médias indicaram que, nas árvores amostradas, as taxas de FBN aumentaram na ordem: solo sob a projeção da copa, filosfera e dermosfera. A maior FBN foi observada na dermosfera de E. edulis...

Tratamento de sementes de soja com níquel para o aumento da fixação biológica e atividade da urease; Nickel soybean seed treatment for improving biological nitrogen fixation and urease activity

Franco, Guilherme de Castro
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 11/03/2015 PT
Relevância na Pesquisa
66.61%
O Níquel (Ni) é um micronutriente para as plantas, por ser componente estrutural das enzimas urease e hidrogenase, que desempenham função no metabolismo do nitrogênio (N) nas plantas leguminosas. A aplicação de Ni via tratamento de semente em soja pode potencializar o processo de fixação biológica de nitrogênio (FBN) com a finalidade de proporcionar maior produção de biomassa da parte aérea e de grãos. Objetivou-se com este trabalho avaliar o efeito da aplicação de doses de Ni, via tratamento de semente, no processo de FBN em plantas de soja, por meio da atividade de nitrogenase (ANase) e da abundância natural de 15N (? 15N?). Foi realizado um experimento em casa de vegetação, em condições controladas. O genótipo de soja BMX POTÊNCIA RR foi cultivado em solo arenoso e submetido à aplicação de 0; 45; 90; 135; 180; 360; e 540 mg kg-1 de Ni aplicado via tratamento de semente. As plantas de soja foram conduzidas até o estádio fenológico R7 (maturação dos grãos). Foram avaliadas a concentração de macro e micronutrientes nas folhas utilizadas para diagnose, determinou-se o teor de clorofila, a atividade enzimática da urease, bem como se quantificou a massa seca de nódulos, no estádio fenológico R1 (Início da floração: até 50% das plantas com flor). Foram ainda determinados: as produções de massa seca de parte aérea e de grãos...

Genetic characterization and nitrogen fixation capacity of Rhizobium strains on common bean

González, Tehuni Orlando; Campanharo, João Carlos; Lemos, Eliana Gertrudes de Macedo
Fonte: Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA) Publicador: Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA)
Tipo: Artigo de Revista Científica Formato: 1177-1184
ENG
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O objetivo deste trabalho foi a caracterização genética de quatro novas estirpes de Rhizobium e a avaliação de sua capacidade de fixação de N2 e nodulação, comparadas a estirpes comerciais e à população nativa de rizóbios de um Latossolo Vermelho. Dois experimentos foram conduzidos em blocos ao acaso, em casa de vegetação. No primeiro experimento, conduzido em tubetes com vermiculita, avaliaram-se a nodulação e a capacidade de fixação das novas estirpes, em comparação com as estirpes comerciais CIAT-899 e PRF-81 e com a população nativa do solo. Das colônias puras isoladas, extraiu-se o DNA genômico e realizou-se o seqüenciamento do espaço intergênico, para a caracterização genética das estirpes e da população nativa de rizóbios. O segundo experimento foi realizado em vasos com solo, para determinação da produtividade e da nodulação do feijoeiro, cultivar Pérola, com o uso das estirpes isoladamente ou em mistura com a PRF-81. A população nativa do solo foi identificada como Rhizobium sp. e se mostrou ineficiente na fixação de nitrogênio. Foram encontradas três espécies de Rhizobium entre as quatro novas estirpes. As estirpes LBMP-4BR e LBMP-12BR estão entre as que têm maior capacidade de nodulação e fixação de N2...

Nodule growth and nitrogen fixation of Calopogonium mucunoides L. show low sensitivity to nitrate

Camargos, Liliane S.; Sodek, Ladaslav
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 167-174
ENG
Relevância na Pesquisa
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It is well established that nitrate is a potent inhibitor of nodulation and nitrogen fixation in legumes. The objective of this study was to demonstrate the relative insensitivity of these processes to nitrate with Calopogonium mucunoides, a tropical South American perennial legume, native to the cerrado (savannah) region. It was found that nodule number was reduced by about half in the presence of high levels of nitrate (15 mM) but nodule growth (total nodule mass per plant) and nitrogen fixation (acetylene reduction activity and xylem sap ureide levels) were not affected. Other sources of N (ammonium and urea) were also without effect at these concentrations. At even higher concentrations (30 mM), nitrate did promote significant inhibition (ca. 50%) of acetylene reduction activity, but no significant reduction in xylem sap ureides was found. The extraordinary insensitivity of nodulation and N2 fixation of C. mucunoides to nitrate suggests that this species should be useful in studies aimed at elucidating the mechanisms of nitrate inhibition of these processes. © 2010 Springer Science+Business Media B.V.

Fixação do nitrogenio em plantas de soja com o sistema radicular alagado; Nitrogen fixation in root-flooded soybean plants

Gilberto Costa Justino
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 28/01/2009 PT
Relevância na Pesquisa
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Muitos solos, principalmente aqueles com baixa capacidade de drenagem, ficam sujeitos ao alagamento após pequenos ou grandes períodos de chuva. Nestas condições, o sistema radicular das plantas sofre estresse por deficiência de O2 em função da baixa taxa de difusão deste gás na água. Quando o teor de O2 no meio fica abaixo do necessário para manter a taxa normal de respiração das raízes ocorre a hipoxia. O sistema radicular das leguminosas que possuem nódulos formados pela associação simbiótica com bactérias do gênero Rhizobium, responsáveis pela fixação de N2 atmosférico, é também adversamente afetado por hipoxia. Muitos estudos sobre alterações metabólicas em raízes, em resposta a hipoxia, têm sido feitos, porém, no caso dos nódulos e da fixação simbiótica de N2 os estudos são escassos. Há evidências de que plantas noduladas sob condições de alagamento apresentam baixas taxas de fixação, o que é atribuído principalmente à baixa disponibilidade de O2, necessário para a produção do ATP usado na fixação de N2, catalisada pela enzima nitrogenase. As técnicas disponíveis para medir a atividade da nitrogenase são inviáveis com os nódulos mantidos submersos na água, pois envolvem a passagem de substratos da enzima pelo sistema radicular...

Genetic characterization and nitrogen fixation capacity of Rhizobium strains on common bean

González,Tehuni Orlando; Campanharo,João Carlos; Lemos,Eliana Gertrudes de Macedo
Fonte: Embrapa Informação Tecnológica; Pesquisa Agropecuária Brasileira Publicador: Embrapa Informação Tecnológica; Pesquisa Agropecuária Brasileira
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2008 EN
Relevância na Pesquisa
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This study aimed to genetically characterize four new Rhizobium strains, and to evaluate their nodulation and fixation capacity compared to commercial strains and to native rhizobia population of a Brazilian Rhodic Hapludox. Two experiments were carried out in randomized blocks design, under greenhouse conditions, in 2007. In the first experiment, the nodulation and nitrogen fixation capacity of new strains were evaluated, in comparison to the commercial strains CIAT-899 and PRF-81 and to native soil population. It was carried out in plastic tubes filled with vermiculite. DNA extractions and PCR sequencing of the intergenic space were made from the isolated pure colonies, in order to genetically characterize the strains and the native rhizobia population. In the second experiment, the nodulation and productivity of common beans Perola cultivar were determined, with the use of evaluated strains, alone or in mixture with PRF-81 strain. It was carried out in pots filled with soil. The native soil population was identified as Rhizobium sp. and was inefficient in nitrogen fixation. Three different Rhizobium species were found among the four new strains. The LBMP-4BR and LBMP-12BR new strains are among the ones with greatest nodulation and fixation capacity and exhibit differential responses when mixed to PRF-81.

Plant densities and modulation of symbiotic nitrogen fixation in soybean

Luca,Marcos Javier de; Hungría,Mariangela
Fonte: São Paulo - Escola Superior de Agricultura "Luiz de Queiroz" Publicador: São Paulo - Escola Superior de Agricultura "Luiz de Queiroz"
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2014 EN
Relevância na Pesquisa
66.6%
Soybean nitrogen (N) demands can be supplied to a large extent via biological nitrogen fixation, but the mechanisms of source/sink regulating photosynthesis/nitrogen fixation in high yielding cultivars and current crop management arrangements need to be investigated. We investigated the modulation of symbiotic nitrogen fixation in soybean [Glycine max (L.) Merrill] at different plant densities. A field trial was performed in southern Brazil with six treatments, including non-inoculated controls without and with N-fertilizer, both at a density of 320,000 plants ha−1, and plants inoculated with Bradyrhizobium elkanii at four densities, ranging from 40,000 to 320,000 plants ha−1. Differences in nodulation, biomass production, N accumulation and partition were observed at stage R5, but not at stage V4, indicating that quantitative and qualitative factors (such as sunlight infrared/red ratio) assume increasing importance during the later stages of plant growth. Decreases in density in the inoculated treatments stimulated photosynthesis and nitrogen fixation per plant. Similar yields were obtained at the different plant densities, with decreases only at the very low density level of 40,000 plants ha−1, which was also the only treatment to show differences in seed protein and oil contents. Results confirm a fine tuning of the mechanisms of source/sink...

Evaluation of the biological nitrogen fixation contribution in sugarcane plants originated from seeds and inoculated with nitrogen-fixing endophytes

Canuto,Erineudo de Lima; Oliveira,André Luis Martinez de; Reis,Verônica Massena; Baldani,José Ivo
Fonte: Sociedade Brasileira de Microbiologia Publicador: Sociedade Brasileira de Microbiologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/11/2003 EN
Relevância na Pesquisa
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The inoculation technique with endophytic diazotrophic bacteria in sugarcane has been shown as an alternative practice to plant growth promotion. The aim of this work was to evaluate the biological nitrogen fixation (BNF) contribution by different strains of Herbaspirillum seropedicae and Gluconacetobacter diazotrophicus in sugarcane plant inoculated from seeds. The seeds were planted in pots filled with non-sterile soil, inoculated with the bacterial strains and grown 10 months outside of the greenhouse. The BNF contribution of the inoculated bacteria varied depending on the plant species used as a control. The highest BNF contribution as well as the highest populations of reisolated bacteria was observed with inoculation of H. seropedicae strains. The roots appeared to be the preferential tissues for the establishment of the inoculated species.

How many metals does it take to fix N2? A mechanistic overview of biological nitrogen fixation

Howard, James B.; Rees, Douglas C.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
66.4%
During the process of biological nitrogen fixation, the enzyme nitrogenase catalyzes the ATP-dependent reduction of dinitrogen to ammonia. Nitrogenase consists of two component metalloproteins, the iron (Fe) protein and the molybdenum-iron (MoFe) protein; the Fe protein mediates the coupling of ATP hydrolysis to interprotein electron transfer, whereas the active site of the MoFe protein contains the polynuclear FeMo cofactor, a species composed of seven iron atoms, one molybdenum atom, nine sulfur atoms, an interstitial light atom, and one homocitrate molecule. This Perspective provides an overview of biological nitrogen fixation and introduces three contributions to this special feature that address central aspects of the mechanism and assembly of nitrogenase.

Phylogenetic analysis of nodulation and nitrogen fixation genes of a brazilian collection of Bradyrhizobium strains.

MENNA, P.; RIBEIRO, R. A.; HUNGRIA, M.
Fonte: In: INTERNATIONAL CONFERENCE ON CULTURE COLLECTIONS, 12., 2010, Florianópolis. Biological Resource Centrers: gateway to biodiversity and services for innovations in biotechnology: proceedings. [S.l]: WFCC, 2010. Publicador: In: INTERNATIONAL CONFERENCE ON CULTURE COLLECTIONS, 12., 2010, Florianópolis. Biological Resource Centrers: gateway to biodiversity and services for innovations in biotechnology: proceedings. [S.l]: WFCC, 2010.
Tipo: Resumo em anais de congresso (ALICE)
EN
Relevância na Pesquisa
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The genus Bradyrhizobium encompasses a variety of bacteria that can live in symbiotic and endophytic associations with legumes and non-legumes, and are characterized by physiological and symbiotic versatility and broad geographical distribution. In studies with Bradyrhizobium strains the comparison of phylogenies of nodulation and housekeeping genes has indicated a monophyletic origin of nodulation genes and diffusion by vertical and horizontal gene transfer, the last one probably influenced by the host plants. In previous studies with the strains analyzed in this study we have shown high diversity in the 16S rRNA, ITS rRNA, atpD, glnII, dnaK and recA housekeeping genes (Menna et al., 2006, 2009). However, despite indications of great genetic variability within the Bradyrhizobium genus, little is known about the phylogeny of the nodulation and nitrogen fixation genes. In this study the nodulation genes nodY/K, nodA and nodZ and the nitrogen fixation gene nifH of forty Bradyrhizobium strains were sequenced and analyzed. The great majority of the strains are from tropical regions and were isolated from members of the three subfamilies and nine tribes of the family Leguminosae (=Fabaceae). In all phylogenetic trees a high level of genetic diversity was observed and several clusters were correlated with the subfamilies of the host plants. One example was with the symbionts of Glycine max and Acacia sp....

Genetic characterization and nitrogen fixation capacity of Rhizobium strains on common bean.

GONZÁLEZ, T.O.; CAMPANHARO, J.C.; LEMOS, E.G. de M.
Fonte: Pesquisa Agropecuária Brasileira, Brasilia, DF, v. 43, n.9, p.1177-1184, set. 2008. Publicador: Pesquisa Agropecuária Brasileira, Brasilia, DF, v. 43, n.9, p.1177-1184, set. 2008.
Tipo: Artigo em periódico indexado (ALICE)
EN
Relevância na Pesquisa
66.47%
This study aimed to genetically characterize four new Rhizobium strains, and to evaluate their nodulation and fixation capacity compared to commercial strains and to native rhizobia population of a Brazilian Rhodic Hapludox. Two experiments were carried out in randomized blocks design, under greenhouse conditions, in 2007. In the first experiment, the nodulation and nitrogen fixation capacity of new strains were evaluated, in comparison to the commercial strains CIAT-899 and PRF-81 and to native soil population. It was carried out in plastic tubes filled with vermiculite. DNA extractions and PCR sequencing of the intergenic space were made from the isolated pure colonies, in order to genetically characterize the strains and the native rhizobia population. In the second experiment, the nodulation and productivity of common beans Perola cultivar were determined, with the use of evaluated strains, alone or in mixture with PRF-81 strain. It was carried out in pots filled with soil. The native soil population was identified as Rhizobium sp. and was inefficient in nitrogen fixation. Three different Rhizobium species were found among the four new strains. The LBMP-4BR and LBMP-12BR new strains are among the ones with greatest nodulation and fixation capacity and exhibit differential responses when mixed to PRF-81.; 2008

Biological Nitrogen Fixation in Agricultural Systems

Metuzals, Jessica
Fonte: Quens University Publicador: Quens University
EN
Relevância na Pesquisa
66.46%
The purpose of this research paper is to assess the effectiveness of Biological Nitrogen Fixation (BNF) as an alternative source of nitrogen (N) in agricultural systems. N is found ubiquitously in the atmosphere, yet often it is the most limiting nutrient for plant growth. Biological Nitrogen Fixation (BNF) is the process by which microorganisms convert atmospheric nitrogen into its plant usable form. The production and transport of chemical fertilizers consumes large amounts of fossil fuels and releases potent greenhouse gases. BNF is a sustainable alternative to conventional N fertilizers that derives its energy from renewable energy sources and enhances nutrient cycling within the soil environment. This paper compares the potential BNF rates of pulses, N2 fixing trees and green manures and limitations. Through comparative analysis, results indicated that methods of utilization are abundant and diverse, thereby facilitating BNF incorporation in a wide range of agricultural systems. Furthermore, social and economic aspects revealed that there is no one size fits all approach. The case studies showed that overall nutrient budgets must be considered to ensure net positive effects and the future of soil nutrient management strategies necessitates integrative approaches.

Variation in the sensitivity of nodulation and nitrogen fixation to nitrate in annual "Medicago" species / by Hossein Heidari Sharif Abad.

Heidari Sharif Abad, Hossein
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado Formato: 119908 bytes; application/pdf
Publicado em //1994 EN
Relevância na Pesquisa
66.35%
Annual species of Medicago, or medics, are important pasture legumes in the neutral to alkaline soils of southern Australia but their nodulation and nitrogen fixation processes are retarded by soil nitrate. This study ascertains whether an observed tolerance to nitrate among medic species can be substantiated, and attempts to understand the underlying factors responsible.; Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, (1995); Bibliography: leaves 153-179.; xvi, 179 leaves : ill. (some col.) ; 30 cm.; Title page, contents and abstract only. The complete thesis in print form is available from the University Library.

The impact of acetohydroxyacid synthase inhibiting herbicides on symbiotic nitrogen fixation of grain and pasture legumes.

Farquharson, Ryan L.
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2010
Relevância na Pesquisa
66.66%
Group B herbicides inhibit the acetohydroxyacid synthase (AHAS - also known as acetolactate synthase) enzyme in the pathway of branched chain amino acid synthesis. These herbicides have gained widespread use in Australia, however potential impacts on nitrogen fixation by legumes have not been comprehensively assessed. Group B herbicides recommended for in-crop application to grain and pasture legume species were assessed for impacts on growth, nodulation and nitrogen fixation. Although it was demonstrated that nitrogen fixation can be affected by these herbicides, the range of responses indicated that multiple mechanisms could be responsible. These could include a reduction nitrogen fixation directly coupled to reduced plant growth; more specific and direct disruption of nitrogen fixation related to the inhibition of nodulation; or other mechanisms yet to be defined that could include affects on the rhizobia. To begin to understand these mechanisms, a herbicide tolerant Medicago littoralis cultivar ‘FEH-1’ was compared to Herald. Decreased nodulation, nitrogen fixation and acetylene reduction activity due to herbicide application were primarily related to the susceptibility of the plant to the herbicide. Thus herbicide tolerant legumes have the potential to alleviate suboptimal nitrogen fixation due to group B herbicides. A proteomics study of the response of root tips of model legume Medicago truncatula A17 to flumetsulam and metsulfuron methyl was conducted to identify more specifically the herbicide impacts on plant physiology. An increased abundance of stress response proteins and a decline in the abundance of some metabolic proteins was found...

Phosphorus availability and elevated CO2 affect biological nitrogen fixation and nutrient fluxes in a clover-dominated sward

Edwards, Everard; McCaffery, Stephanie; Evans, John
Fonte: Cambridge University Press Publicador: Cambridge University Press
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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• The response of biological nitrogen fixation (BNF) to elevated CO2 was examined in white clover (Trifolium repens)-dominated swards under both high and low phosphorus availability. • Mixed swards of clover and buffalo grass (Stenotaphrum secundatum)

Variability in symbiotic nitrogen fixation in common bean

Rodiño Míguez, Ana Paula; Santalla Ferradás, Marta; González Fernández, Ana María; Drevon, Jean-Jacques; Ron Pedreira, Antonio Miguel de
Fonte: Bean Improvement Cooperative Publicador: Bean Improvement Cooperative
Tipo: Artículo Formato: 259109 bytes; application/pdf
ENG
Relevância na Pesquisa
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Yield responses of bean are often limited by the nitrogen deficiency, being the most common limiting factor for the growth of the plants. Common bean (Phaseolus vulgaris L.) is often considered as a poor N2-fixing legume. Thus, it is often cultivated with a complement of mineral nitrogenous fertilization to correct this deficiency and to raise the yields. The symbiotic nitrogen fixation (SNF) provides an ecologically acceptable alternative to the high applications of nitrogenous fertilizers, especially in Europe, and an economic alternative to the limited access to these fertilizers in the developing countries. The objectives of the work are i) to study the genotypic diversity represented by local populations of bean, ii) to identify those populations which can be useful to improve SNF potential as well as iii) to determine the degree of genetic diversity of the native populations of rhizobia that nodulate P. vulgaris in the soils of Galicia and their potential to fix N2 with local populations of bean.; Research was supported by the projects INTRAMURAL CSIC 200110E016 and PHASEORHIZ FP6-510564 from the EU. The authors thank the Xunta de Galicia for funding.; Peer reviewed

Nitrogen Fixation By Corona Discharge On The Early Precambrian Earth

Nna Mvondo, Delphine; Navarro-González, Rafael; Raulin, François; Coll, Patrice
Fonte: Springer Publicador: Springer
Tipo: Artículo Formato: 332124 bytes; application/pdf
ENG
Relevância na Pesquisa
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9 pages, 3 figures.; The original publication is available at www.springerlink.com; We report the first experimental study of nitrogen fixation by corona discharge on the anoxic primitive Earth. The energy yields of nitric oxide (NO) and nitrous oxide (N2O) were experimentally determined over a wide range of CO2-N2 mixtures simulating the evolution of the Earth's atmosphere during the Hadean and Archean eras (from 4.5 ba to 2.5 ba). NO, the principal form of fixed nitrogen in lightning and coronal discharge in early Earth, is produced ten times less efficiently in the latter type of electrical discharge with an estimated maximum annual production rate of the order of 10^10 g/yr. For N2O the maximum production rate was estimated to be ∼109 g/yr. These low rates of syntheses indicate that corona discharges as point discharges on the clouds and ground did not play a significant role in the overall pool of reactive nitrogen needed for the emergence and sustainability of life.; This paper describes research supported by the National Autonomous University of Mexico (DGAPA-IN102796), the National Council of Science and Technology of Mexico (CONACyT 32531-T), the French-Mexican scientific research program ECOS/CONACyT-SEP-ANNUIES (M97U01).; Peer reviewed

A possible nitrogen crisis for Archaean life due to reduced nitrogen fixation by lightning

Navarro-González, Rafael; McKay, Christopher P.; Nna Mvondo, Delphine
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artículo Formato: 174057 bytes; application/pdf
ENG
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4 pages, 2 figures.-- PMID: 11452304 [PubMed].; Nitrogen is an essential element for life and is often the limiting nutrient for terrestrial ecosystems. As most nitrogen is locked in the kinetically stable form, N2, in the Earth's atmosphere, processes that can fix N2 into biologically available forms —such as nitrate and ammonia— control the supply of nitrogen for organisms. On the early Earth, nitrogen is thought to have been fixed abiotically, as nitric oxide formed during lightning discharge. The advent of biological nitrogen fixation suggests that at some point the demand for fixed nitrogen exceeded the supply from abiotic sources, but the timing and causes of the onset of biological nitrogen fixation remain unclear. Here we report an experimental simulation of nitrogen fixation by lightning over a range of Hadean (4.5–3.8 Gyr ago) and Archaean (3.8–2.5 Gyr ago) atmospheric compositions, from predominantly carbon dioxide to predominantly dinitrogen (but always without oxygen). We infer that, as atmospheric CO2 decreased over the Archaean period, the production of nitric oxide from lightning discharge decreased by two orders of magnitude until about 2.2 Gyr. After this time, the rise in oxygen (or methane) concentrations probably initiated other abiotic sources of nitrogen. Although the temporary reduction in nitric oxide production may have lasted for only 100 Myr or less...