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The study of plant-microbe interactions is a rapidly growing research field, with increasing attention to the role of seed-borne microbial endophytes in protecting the plant during its development from abiotic and biotic stresses. Recent evidence suggests that seed microbiota is crucial in establishing the plant microbial community, affecting its composition and structure, and influencing plant physiology and ecology. For Theobroma cacao L., the diversity and composition of vertically transmitted microbes have yet to be addressed in detail. We explored the composition and diversity of seed-borne endophytes in cacao pods of commercial genotypes (ICS95, IMC67), recently liberated genotypes from AGROSAVIA (TCS01, TCS19), and landraces from Tumaco (Colombia) (AC9, ROS1, ROS2), to evaluate microbial vertical transmission and establishment in various tissues during plant development. We observed a higher abundance of Pseudomonas and Pantoea genera in the landraces and AGROSAVIA genotypes, while the commercial genotypes presented a higher number of bacteria species but in low abundance. In addition, all the genotypes and plant tissues showed a high percentage of fungi of the genus Penicillium. These results indicate that domestication in cacao has increased bacterial endophyte diversity but has reduced their abundance. We isolated some of these seed-borne endophytes to evaluate their potential as growth promoters and found that Bacillus, Pantoea, and Pseudomonas strains presented high production of indole acetic acid and ACC deaminase activity. Our results suggest that cacao domestication could lead to the loss of essential bacteria for seedling establishment and development. This study improves our understanding of the relationship and interaction between perennial plants and seed-borne microbiota.

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High rates of fluorosis were reported worldwide as a result of human consumption of water with fluoride contents. Adjusting fluoride concentration in water as recommended by the World Health Organization (<1.5 mg L-1) is a concern and it needs to be conducted through inexpensive, but efficient techniques, such as phytoremediation. The application of phytohormones was investigated as a strategy to improve this process. Thus, the main goal of this research was to evaluate the effect of exogenous auxin and gibberellin on the tropical duckweed Eichhornia crassipes performance for fluoride phytoremediation. Definitive screening and central composite rotatable designs were used for experiments where fluoride concentration (5~15 mg L-1), phosphorus concentration (1~10 mg L-1), and pH (5~9) were assessed as well throughout 10 days. Fluoride contents were determined in solution and plant tissues by potentiometry. Higher concentrations of fluoride reflected on greater absorptions by plants, though in relative terms removal efficiencies were quite similar for all treatments (~60%). Auxin and acidic conditions favored fluoride removals per mass of plant. Fluoride accumulated mostly in leaves and auxin probably alleviated toxic effects on E. crassipes while gibberellin showed no effect. Therefore, E. crassipes could be employed as a fluoride accumulator plant for water treatment and exogenous auxin may be used to improve the process.

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The genera Bacillus belongs to the group of microorganisms that are known as plant growth-promoting bacteria, their metabolism has evolved to produce molecules that benefit the growth of the plant, and the production of 3-indole acetic acid (IAA) is part of its secondary metabolism. In this work, Bacillus subtilis was cultivated in a bioreactor to produce IAA using propionate and glucose as carbon sources in an M9-modified media; in both cases, tryptophan was added as a co-substrate. The yield of IAA using propionate is 17% higher compared to glucose. After 48 h of cultivation, the final concentration was 310 mg IAA/L using propionate and 230 mg IAA/L using glucose, with a concentration of 500 mg Trp/L. To gain more insight into propionate metabolism and its advantages, the genome-scale metabolic model of B. subtilis (iBSU 1147) and computational analysis were used to calculate flux distribution and evaluate the metabolic capabilities to produce IAA using propionate. The metabolic fluxes demonstrate that propionate uptake favors the production of precursors needed for the synthesis of the hormone, and the sensitivity analysis shows that the control of a specific growth rate has a positive impact on the production of IAA.

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Endophytic bacteria Bacillus safensis RS95 and Pseudomonas hibiscicola RS121 were evaluated for their ability to promote the growth of rice seedlings and produce indole-acetic acid (IAA) and siderophores and to solubilize phosphates. 'Guri' rice seeds were immersed in bacterial endophyte cell suspensions (separated and two-strain mixed), as well as in Escherichia coli DH5α, phosphate-buffered saline (PBS) and water treatments (negative controls). Seeds were sown on agar-water in Petri plates placed vertically at an angle of 65°. The ability of plant growth-promoting endophytic bacteria (PGPEB) to produce IAA and siderophores was determined by Salkowski colorimetric and chrome azurol S (CAS) assays, respectively. Mineral phosphate solubilization activity was calculated by inoculating the endophytes onto medium containing insoluble phosphate. PGPEB showed a positive effect on the growth of rice seedlings, causing a mean growth of shoots and primary-roots of 60 and 67%, respectively. Bacterial strains also showed positive traits for IAA and siderophore production, as well as phosphate-solubilization activity

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ABSTRACT In the present study, 62 endophytic bacterial strains of cedar seeds (Cedrela odorata L.), collected in the municipalities of Huehuetán, Motozintla, and Pijijiapan in the state of Chiapas, Mexico were isolated. The goal was to identify characteristics of biotechnological interest such as biocontrol, promotion ofplant growth, and growth in aromatic compounds. The strains were identified by the partial sequence of the 16S ribosomal gene as belonging to the Bacillus genus. The biocontrol capacity of phytopathogenic fungi, production of indoleacetic acid (IAA), solubilization of phosphate, and growth in xenobiotic compounds (phenanthrene, benzene, anthracene, or phenol) were detected in 26 strains of the 62 isolates. 21 % of the strains inhibited the mycelial growth of Alternaria solani and Fusarium sp., and 13 % of the Phytophthora capsici oomycete. IAA production was detected in 24 isolates, phosphate solubilizing activity was identified in 18 isolates, while the ability to grow in the presence of phenanthrene and benzene was found in 26 isolates; 24 isolates grew in the presence of anthracene and only two isolates grew in phenol as the only carbon sources. This is the first report of the isolation and identification of endophytic bacteria from cedar seeds, where biotechnological characteristics were detected for biological control, promotion of plant growth, and growth in the presence of xenobiotic compounds.

RESUMEN En el presente estudio se aislaron 62 cepas bacterianas endófitas de semillas de cedro (Cedrela odorata L.) colectadas en los municipios de Huehuetán, Motozintla y Pijijiapan en el estado de Chiapas, México, con el objetivo de identificar características de interés biotecnológicas como biocontrol, promoción del crecimiento vegetal y crecimiento en compuestos aromáticos. Las cepas se identificaron por la secuencia parcial del gen 16S ribosomal como pertenecientes al género Bacillus. En 26 cepas de las 62 aisladas se detectaron la capacidad de biocontrol de hongos fitopatógenos, la producción de ácido indolacético (AIA), la solubilización de fosfato y el crecimiento en compuestos xenobióticos (fenantreno, benceno, antraceno o fenol). El 21 % de las cepas inhibió el crecimiento miceliar de Alternaria solani y Fusarium sp., y el 13 % del oomiceto Phytophthora capsici. La producción de ácido indolacético se detectó en 24 aislados y la actividad solubilizadora de fosfato se encontró en 18 aislados, mientras que la capacidad de crecer en presencia de fenantreno y benceno se manifestó en 26 aislados (24 aislados crecieron en presencia de antraceno y solo dos aislados crecieron en fenol como únicas fuentes de carbono). Es importante mencionar que este es el primer reporte del aislamiento e identificación de bacterias endófitas de semillas de cedro, en el que se detectaron características biotecnológicas para el control biológico, la promoción del crecimiento vegetal y el crecimiento en presencia de compuestos xenobióticos.

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An Egyptian rhizobacterium Azospirillum sp. isolated from Sadat city was able to produce indole acetic acid (IAA) up to (30.59 µg/ml). The isolate was identified biochemically and by 16S rRNA sequencing which showed 99.9% similarity to Azospirillum brasilense. The new isolate has been registered in Genbank with accession number MH179119.1. Extracted IAA was used as reducing or stabilizing agent of sliver nanoparticles (AgNPs). Successful fabrication of biogenic IAA-AgNPs was confirmed by Fourier Transform Infrared Spectrophotometer (FTIR) analysis of IAA which showed absorbance peak at 3434.78 cm-1 due to the N-H stretch of primary amines. Highly resolution Transmission Electron Microscopy (HR-TEM) showed AgNPs coating or capping with IAA in spherical shaped with size ranged from 6.01 to 44.02 nm. Energy dispersive X-ray (EDX) analysis revealed that Ag+ ions were attached to the surface of IAA-AgNPs particles. HR-TEM examination showed cell wall damage of Citrobacter freundii cells after exposure to IAA-AgNPs leading to cell death. In vivo results showed that C. freundii infection of rats induced significant increase in liver and kidney functions and deleterious histopathological alteration in rat's tissues. However, treatment by extracted IAA and IAA-AgNPs could normalize the biochemical and histopathological alterations occurred in infected rats. This is the first study to prove that IAA extracted from Azospirillum brasilense is a hopeful capping agent for NPs which has potential to protect against pathogenic infections, nontoxic and/or safe on rat's metabolisms.

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Strains of Bacillus thuringiensis (Bt) are commonly commercialized as bioinoculants for insect pest control, but their benefits go beyond their insecticidal property: they can act as plant growth-promoters. Auxins play a major role in the plant growth promotion. However, the mechanism of auxin production by the Bacilli group, and more specifically by Bt strains, is unclear. In previous work, the plant growth-promoting rhizobacterium (PGPR) B. thuringiensis strain RZ2MS9 increased the corn roots. This drew our attention to the strain's auxin production trait, earlier detected in vitro. Here, we demonstrate that in its genome, RZ2MS9 harbours the complete set of genes required in two pathways that are used for Indole acetic acid (IAA) production. We also detected that the strain produces almost five times more IAA during the stationary phase. The bacterial application increased the shoot dry weight of the Micro-Tom (MT) tomato by 24%. The application also modified MT root architecture, with an increase of 26% in the average lateral root length and inhibition of the axial root. At the cellular level, RZ2MS9-treated MT plants presented elongated root cortical cells with intensified mitotic activity. Altogether, these are the best characterized auxin-associated phenotypes. Besides that, no growth alteration was detected in the auxin-insensitive diageotropic (dgt) plants either with or without the RZ2MS9 inoculation. Our results suggest that auxins play an important role in the ability of B. thuringiensis RZ2MS9 to promote MT growth and provide a better understanding of the auxin production mechanism by a Bt strain.

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The aim of the study was to characterize halotolerant bacteria and to evaluate their plant growth promotion potential on chia and quinoa seedlings under saline stress. Isolated microorganisms were evaluated for nitrogen fixation, phosphate solubilization, and production of siderophores and indole acetic acid. Three strains and two consortia were selected: Halomonas sp. (SFS), Micrococcus luteus (SA211), Bacillus sp. (HX11), C1 (SA211 + SFS), and C2 (SA211 + HX11). In vitro assays using water agar and half-strength Murashige-Skoog plates showed that an increase in salinity led to an increased seedlings mortality and a decrease in germination (lower than 40%), in total length (varying between 16% and 87% decreases), root length (from 60% to 92% lesser length) and dry weight (from 7% to 86% lower weight). Also, the relative growth index (RGI) decreased for both crops in most treatments, except those with HX11 and C2. These treatments had the highest growth parameters and RGI values in presence of high salinity in chia (50 and 100 mmol/L NaCl) and quinoa (200 and 400 mmol/L NaCl). SA211, the highest producer of indole acetic acid, showed a detrimental effect and anomalous phenotype on plants. Our results suggest that Bacillus sp. HX11, with multiple plant growth promotion traits and tolerance to saline stress, has a great potential as a bioinoculant in saline conditions and could be used as a biofertilizer for crop production.

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This study aimed to evaluate the genetic diversity of bacterial community associated to different sugarcane genotypes, association habitat and phenological phase of the culture, as well as to isolate, to identify and to characterize your potential for plant growth-promoting. Root and rhizospheric soil samples from RB 92579 and RB 867515 varieties were collected at 120 and 300 days after regrowth (DAR). The diversity of bacterial was evaluated through of the 16S rRNA and nifH genes. We found greater genetic diversity in the root endophytic habitat at 120 DAR. We identify the genera Burkholderia sp., Pantoea sp., Erwinia sp., Stenotrophomonas sp., Enterobacter sp. and Pseudomonas sp. The genera Bacillus sp. and Dyella sp. were only identified in the variety RB 92579. We found indices above 50% for biological nitrogen fixation, production of indole acetic acid and phosphate solubilization, showing that the use of these bacteria in biotechnological products is very promising.

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Chlorothalonil is a commonly used fungicide to control the karnal bunt caused by Tilletia indica Mitra in wheat production from the Yaqui Valley, Mexico. Here, the effect of Chlorothalonil on the growth of 132 bacterial strains associated with wheat rhizosphere from the Yaqui Valley was evaluated, as well as their ability to produce indoles. Thirty-three percent of the evaluated strains were inhibited by Chlorothalonil, being Bacillus and Paenibacillus the most inhibited genera, observing an inhibition >50% of their strains. In addition, 49% of the inhibited strains showed the ability to produce indoles (>5 µg/mL), where the genus Bacillus was the most abundant (80%). The remaining strains (67%) were tolerant to the evaluated fungicide, but only 37% of those showed the ability to produce indoles, which could be considered as Plant Growth Promoting Rhizobacteria (PGPR). These results showed that Chlorothalonil is not only an antifungal compound but also inhibits the growth of bacterial strains with the ability to produce indoles. Thus, the intensive application of fungicides to agro-systems needs more validation in order to develop sustainable agricultural practices for food production.

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Few studies have evaluated endophytic bacteria in relation to plant growth promotion, nitrogen uptake and biological control. The aim of this study was to molecularly and physiologically characterize thirteen endophytic bacteria strains, evaluate their biological control properties and their ability to promote plant growth and plant N nutrition. All the strains produced indole acetic acid and promoted increase of plant biomass, N accumulative amount and N-use efficiency index. None of the strains carries the nifH gene. Four strains stimulated plant nitrate reductase activity, four solubilized phosphate, nine produced siderophores and none produced HCN. Seven strains inhibited Bipolaris sacchari growth and one was antagonistic to Ceratocystis paradoxa. The pathogens were inhibited by the production of diffusible and volatile metabolites by the bacterial strains. Moreover, this is the first study to demonstrate the effect of Delftia acidovorans on sugarcane plant growth, nitrogen metabolism improvement and antagonism to B. sacchari. The most efficient strains in promoting plant growth and exhibiting antagonistic activities towards fungal pathogens were Herbaspirillum frinsingense (IAC-BECa-152) and three Pantoea dispersa strains (IAC-BECa-128, IAC-BECa-129, and IAC-BECa-132). These bacteria show potential to be used as inoculants for sustainable agricultural management, mainly at the seedling production phase.

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Bacterial endophytes are considered to have a beneficial effect on host plants, improving their growth by different mechanisms. The objective of this study was to investigate the capacity of four endophytic Bacillus strains to solubilize iron phosphate (Fe-P), produce siderophores and indole-acetic acid (IAA) in vitro, and to evaluate their plant growth promotion ability in greenhouse conditions by inoculation into pearl millet cultivated in a P-deficient soils without P fertilization, with Araxá rock phosphate or soluble triple superphosphate. All strains solubilized Fe-P and three of them produced carboxylate-type siderophores and high levels of IAA in the presence of tryptophan. Positive effect of inoculation of some of these strains on shoot and root dry weight and the N P K content of plants cultivated in soil with no P fertilization might result from the synergistic combination of multiple plant growth promoting (PGP) traits. Specifically, while B1923 enhanced shoot and root dry weight and root N P content of plants cultivated with no P added, B2084 and B2088 strains showed positive performance on biomass production and accumulation of N P K in the shoot, indicating that they have higher potential to be microbial biofertilizer candidates for commercial applications in the absence of fertilization.

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Abstract Bacterial endophytes are considered to have a beneficial effect on host plants, improving their growth by different mechanisms. The objective of this study was to investigate the capacity of four endophytic Bacillus strains to solubilize iron phosphate (Fe-P), produce siderophores and indole-acetic acid (IAA) in vitro, and to evaluate their plant growth promotion ability in greenhouse conditions by inoculation into pearl millet cultivated in a P-deficient soils without P fertilization, with Araxá rock phosphate or soluble triple superphosphate. All strains solubilized Fe-P and three of them produced carboxylate-type siderophores and high levels of IAA in the presence of tryptophan. Positive effect of inoculation of some of these strains on shoot and root dry weight and the N P K content of plants cultivated in soil with no P fertilization might result from the synergistic combination of multiple plant growth promoting (PGP) traits. Specifically, while B1923 enhanced shoot and root dry weight and root N P content of plants cultivated with no P added, B2084 and B2088 strains showed positive performance on biomass production and accumulation of N P K in the shoot, indicating that they have higher potential to be microbial biofertilizer candidates for commercial applications in the absence of fertilization.

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Abstract Bacterial endophytes are considered to have a beneficial effect on host plants, improving their growth by different mechanisms. The objective of this study was to investigate the capacity of four endophytic Bacillus strains to solubilize iron phosphate (Fe-P), produce siderophores and indole-acetic acid (IAA) in vitro, and to evaluate their plant growth promotion ability in greenhouse conditions by inoculation into pearl millet cultivated in a P-deficient soils without P fertilization, with Araxá rock phosphate or soluble triple superphosphate. All strains solubilized Fe-P and three of them produced carboxylate-type siderophores and high levels of IAA in the presence of tryptophan. Positive effect of inoculation of some of these strains on shoot and root dry weight and the N P K content of plants cultivated in soil with no P fertilization might result from the synergistic combination of multiple plant growth promoting (PGP) traits. Specifically, while B1923 enhanced shoot and root dry weight and root N P content of plants cultivated with no P added, B2084 and B2088 strains showed positive performance on biomass production and accumulation of N P K in the shoot, indicating that they have higher potential to be microbial biofertilizer candidates for commercial applications in the absence of fertilization.

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Bacterial endophytes are considered to have a beneficial effect on host plants, improving their growth by different mechanisms. The objective of this study was to investigate the capacity of four endophytic Bacillus strains to solubilize iron phosphate (Fe-P), produce siderophores and indole-acetic acid (IAA) in vitro, and to evaluate their plant growth promotion ability in greenhouse conditions by inoculation into pearl millet cultivated in a P-deficient soils without P fertilization, with Araxá rock phosphate or soluble triple superphosphate. All strains solubilized Fe-P and three of them produced carboxylate-type siderophores and high levels of IAA in the presence of tryptophan. Positive effect of inoculation of some of these strains on shoot and root dry weight and the N P K content of plants cultivated in soil with no P fertilization might result from the synergistic combination of multiple plant growth promoting (PGP) traits. Specifically, while B1923 enhanced shoot and root dry weight and root N P content of plants cultivated with no P added, B2084 and B2088 strains showed positive performance on biomass production and accumulation of N P K in the shoot, indicating that they have higher potential to be microbial biofertilizer candidates for commercial applications in the absence of fertilization.(AU)

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ABSTRACT Rhizobium-legume symbioses play relevant roles in agriculture but have not been well studied in Ecuador. The aim of this study was to characterize the genetic and phenotypic diversity of Rhizobium isolates associated with Phaseolus vulgaris from southern Ecuador. Morpho-cultural characterization, biochemical tests and physiological analyses were conducted to authenticate and determine the diversity of bacteria Rhizobium-like isolates. The genetic diversity of the isolates was determined by molecular techniques, which consisted of bacteria DNA extraction and amplification and sequencing of the 16S rRNA gene. The nodulation parameters and nitrogen fixation for P. vulgaris under greenhouse conditions were also assessed to determine the phenotypic diversity among isolates. Furthermore, bacteria indole-acetic-acid production was evaluated by the colorimetric method. Morpho-cultural and biochemical characteristic assessments demonstrated that Rhizobium-like bacteria was associated with the P. vulgaris nodules. The diversity among the isolates, as determined by physiological analyses, revealed the potential of several isolates to grow at different pH values, salinity conditions and temperatures. Partial sequencing of the 16S rRNA gene identified the Rhizobium genus in every sampling site. From a total of 20 aligned sequences, nine species of Rhizobium were identified. Nodule formation and biomass, as well as nitrogen fixation, showed an increase in plant phenotypic parameters, which could be influenced by IAA production, especially for the strains R. mesoamericanum NAM1 and R. leguminosarum bv. viciae COL6. These results demonstrated the efficiency of native symbiotic diazotrophic strains inoculants for legume production. This work can serve as the basis for additional studies of native Rhizobium strains and to help spread the use of biofertilizers in Ecuadorian fields.

RESUMO A simbiose Rhizobium-leguminosa desempenha um relevante papel na agricultura, entretanto não tem recebido suficiente atenção de estudos científicos no Equador. O objetivo deste artigo foi caracterizar a diversidade genética e fenotípica de isolados de Rhizobium associados com Phaseolus vulgaris do sul do Equador. A caracterização morfo-cultural, testes bioquímicos e análises fisiológicas foram realizados para autenticar e determinar a diversidade de isolados de bactérias Rhizobium. A diversidade genética foi determinada por por técnicas moleculares consistindo na extração de DNA genômico bacteriano, amplificação e sequenciamento parcial do gene 16SrRNA; e parâmetros de nodulação e fixação de nitrogênio de P. vulgaris sobre condições de estufa foram testados para determinar a diversidade fenotípica entre os isolados. Além disso, a produção de ácido indolacético foi avaliada por um método colorimétrico. A análise fisiológica da diversidade entre os isolados revelou o potencial de crescimento de diversos isolados em diferentes níveis de pH, salinidade e temperatura. O sequenciamento parcial do gene 16S rRNA mostrou o gênero Rhizobium em todas os locais de amostragem. De um total de 20 sequências alinhadas, 9 espécies de Rhizobium foram identificadas. A formação de nódulos e biomassa, bem como a fixação de nitrogênio mostraram um aumento nos parâmetros fenotípicos das plantas, os quais devem ser influenciados pela produção de IAA, especialmente pelas cepas R. mesoamericanum NAM1 e R. leguminosarum bv. viciae COL6. Estes resultados demonstram a eficiência de cepas diazotróficas simbióticas nativas para produção de inoculantes para leguminosas e fornece informações valiosas e uteis para a agricultura sustentável equatoriana. Neste sentido, este trabalho deve ser um elemento essencial para a realização de futuras pesquisas aplicadas relacionadas a cepas Rhizobium nativas e espalhar o uso de biofertizantes em campos equatorianos.

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RESUMEN Con el propósito de evaluar el efecto de tres concentraciones de ácidos húmicos (AH) 1, 10, 100 mg/L contra una concentración de ácido indol acético (AIA), sobre la producción de biomasa, pigmentos, proteínas, carbohidratos y lípidos de A. platensis; se realizaron cultivos en discontinuo en medio Zarrouk 25% suplementados con AH y AIA, bajo condiciones de aireación constante y fotoperiodos de 12:12 horas, durante 30 días. Se encontró que la producción máxima de biomasa fue mayor en el cultivo suplementado con 10 mg/L de AH, comparado con el control y los cultivos suplementados con AIA. De la misma manera fue observado en este tratamiento la producción más alta de pigmentos, proteínas y carbohidratos. Por tanto, se logró incrementar el crecimiento y la producción de metabolitos de A. platensis, lo cual permite observar el uso potencial de estas sustancias como estimulantes biológicos orgánicos.

ABSTRACT The purpose of this research was to evaluate the effect of three concentrations of humic acids (HA) 1, 10, 100 mg/L against a concentration of indole acetic acid (IAA) on production of biomass, pigments, proteins, carbohydrates and lipids of A. platensis. Cultures discontinuous in Zarrouk 25% medium supplemented with HA and IAA under conditions of aeration constant and photoperiod from 12:12 hours, during 30 days were made. It was found that the maximum biomass production was higher in the culture supplemented with 10 mg / L of AH, compared to the control and cultures supplemented with AIA. In the same way the highest production of pigments, proteins and carbohydrates were observed in this treatment. Therefore, the growth and production of metabolites of A. platensis was increased, which makes it possible to observe the potential use of these substances as organic biological stimulants.

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Melatonin is an environmentally friendly-molecule with a potent free radical scavenger and antioxidant capacity. Two pot experiments were conducted during two successive winter seasons (2011/2012 and 2012/2013) at the wire-house of the National Research Centre, Dokki, Cairo, Egypt to study the potentiality of melatonin (100 mM and 500 mM) in alleviating the harmful effect of diluted seawater at a relatively low and high concentrations (3.85 dS/m and 7.69 dS/m, respectively) on the performance of faba bean plants. The results revealed that irrigation of faba bean plants with diluted seawater reduced growth parameters (plant height, leaves number/plant, fresh and dry weights of plant), relative water content (RWC), photosynthetic pigments (chlorophylls a, b and carotenoids), indole acetic acid, total carbohydrate, K+,Ca+2, as well as the ratios of K+/Na+ and Ca+2/Na+. Thiswasaccompanied by significant increases in phenolic content, compatible solutes (total soluble carbohydrate, free amino acids, proline), Na+ and Cl- relative to the control plants (untreated plants). On the other hand, melatonin treatments improved growth parameters, RWC, photosynthetic pigments, total carbohydrate, total phenolic content, indole acetic acid, K+,Ca+2 as well as K+/Na+ and Ca+2/Na+ ratios, either in the plants irrigated with tap water or with diluted seawater, as compared with corresponding controls. Meanwhile, melatonin treatments reduced the levels of compatible solutes, as well as Na+ and Cl- contents, relative to those of corresponding controls. Salinity stress and/ or melatonin treatments induced the production of new protein bands that did not occur in the control plants. Melatonin at 500 mM had a more pronounced effect in alleviating the adverse effects of the two salinity levels under study on the performance of faba bean plants than 100 mM melatonin.

La melatonina es una molécula ambientalmente amigable con una potente capacidad antioxidante y de trampa de radicales libres. Dos experimentos en materas fueron realizados en dos inviernos consecutivos (2011/2012 y 2012/2013) en instalaciones del Centro Nacional de Investigaciones, Dokki, Cairo, Egipto, para estudiar el potencial de la melatonina (100 mM and 500 mM) para disminuir los efectos nocivos del agua de mar diluida a concentraciones relativamente bajas y altas (3,85 dS/m and 7,69 dS/m, respectivamente). Los resultados mostraron que la irrigación de plantas de haba con agua de mar diluida reduce los parámetros de crecimiento (altura de la planta, número de hojas/planta, peso fresco y seco de la planta), el contenido relativo de agua (RWC), los pigmentos fotosintéticos (clorofilas a, b y carotenoides), el ácido indo lacético, los carbohidratos totales, K+, Ca+2, al igual que las relaciones K+/Na+ y Ca2+/Na+. Esto fue acompañado por un incremento significativo en el contenido de fenoles, solutos compatibles (carbohidratos solubles totales, aminoácidos libres, prolina), Na+ y Cl- en comparación con las plantas control (plantas no tratadas). De otro lado, los tratamientos con melatonina mejoraron los parámetros de crecimiento, RWC, los pigmentos fotosintéticos, carbohidratos totales, contenido fenólico total, ácido indo acético, K+,Ca+2 al igual que las relaciones K+/Na+ y Ca+2/Na+ , tanto en las plantas irrigadas con agua dulce de la llave como en las irrigadas con agua de mar diluida en comparación con los controles correspondientes. De otro lado, los tratamientos con melatonina redujeron los niveles de solutos compatibles, al igual que los contenidos de Na+ y Cl-, en comparación con los controles. El estrés por salinidad y/o los tratamientos con melatonina indujeron la producción de nuevas bandas de proteínas que no estuvieron presentes en las plantas control. El tratamiento de melatonina 500 mM tuvo un efecto más pronunciado que el tratamiento de 100 mM en disminuir los efectos adversos de los dos niveles de salinidad estudiados sobre el comportamiento de las plantas de haba.

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Indole-3-acetic acid (IAA) bound is considered a storage molecule and is inactive. However, some studies have proposed an additional possible regulatory mechanism based on the ability of lectins to form complexes with IAA. We report the first crystal structure of ConM in complex with IAA at 2.15 Å resolution. Based on a tetrameric model of the complex, we hypothesize how the lectin controls the availability of IAA during the early seedling stages, indicating a possible new physiological role for these proteins. A free indole group is also bound to the protein. The ConM interaction with different forms of IAA is a strategy to render the phytohormone unavailable to the cell. Thus, this new physiological role proposed for legume lectins might be a novel mechanism by which IAA levels are decreased in addition to the destruction and formation of new complexes in the later stages of seed germination.

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A cana-de-açúcar é uma fonte importante de alimento e bioenergia. Assim, o estudo da interação com bactérias endofíticas que fixam o nitrogênio atmosférico (FBN) e produzem o ácido indol acético (AIA) vem sendo amplamente explorado. Porém, devido à sensibilidade bacteriana, tanto a produção de AIA, como a FBN, podem sofrer o impacto de fatores edafoclimáticos. O objetivo deste trabalho foi avaliar a influência de diferentes concentrações de NaCl sobre o crescimento bacteriano, a FBN e a produção de AIA in vitro de linhagens bacterianas do gênero Burkholderia, isoladas endofiticamente de plantas de cana-de-açúcar, cultivadas no estado de Pernambuco. Para tanto, duas linhagens bacterianas endofíticas das espécies Burkholderia gladioli e B. heleia foram inoculadas em meio TSA (com L-triptofano) acrescido de cinco concentrações de NaCl: 0,1; 1; 10; 25 e 50 g.L-1 e incubadas sob agitação. O crescimento bacteriano e a produção de AIA foram avaliados através de um espectrofotômetro por 48 horas. Para o teste de fixação de nitrogênio, as linhagens foram inoculadas em meio LGI-P semi-sólido acrescido de cinco concentrações de NaCl: 0,1; 1; 10; 25 e 50 g.L1 e incubadas a 28ºC por 10 dias. Foi possível observar que altas concentrações de NaCl influenciaram negativamente o crescimento bacteriano e a produção do AIA in vitro por B. glaidoli e B. heleia. E que, concentrações de NaCl acima de 25 g.L-1 inibiram a capacidade de fixar nitrogênio, de ambas as linhagens.

The sugarcane is an important source of food and bioenergy. So, the study of its interaction with endophytic bacteria that fix atmospheric nitrogen (BNF) and produce indole acetic acid (IAA) has been widely explored. However, due to bacterial sensitivity, both the production of IAA as the BNF may suffer the impact of soil and climatic factors. The goal of this study was to evaluate the influence of the NaCl different concentrations on the bacterial growth, on the BNF and on the IAA production in vitro by endophytic bacterial strains of the genus Burkholderia isolated from sugarcane plants grown in the Pernambuco State. In this study, two endophytic bacterial strains of Burkholderia gladioli and B. heleia species were inoculated in TSA (with L-tryptophan) added of five NaCl concentrations: 0.1, 1, 10, 25 and 50 g.L-1 and incubated under agitation. Bacterial growth and IAA production were assessed using a spectrophotometer for 48 hours. The nitrogen fixation test was carried out by the inoculation of the bacteria in semi-solid LGP-I added of five NaCl concentrations: 0.1, 1, 10, 25 and 50 g.L-1 and incubated at 28°C during 10 days. It was observed that high concentrations of NaCl influenced negatively the bacterial growth and indole acetic acid production in vitro by B. glaidoli and B. heleia. Nevertheless, NaCl concentrations above 25 g.L-1 inhibited the ability to fix nitrogen in both strains.

Assuntos