What Do We Know About the Publications Related with Azospirillum? A Metadata Analysis.

Azospirillum is one of the most successful plant growth-promoting bacteria (PGPB) genera and it is considered a study model for plant-bacteria interactions. Because of that, a wide broad of topics has been boarded and discussed in a significant number of publications in the last four decades. Using the Scopus® database, we conducted a bibliographic search in order to analyze the number and type of publications, the authors responsible of these contributions, and the origin of the researchers, as well as the keywords and journals selected by the authors, among other related characteristics, with the aim to understand some less addressed details about the work done with Azospirillum worldwide since its discovery in 1925. Despite that the largest numbers of publications about this bacterium were obtained between the 1970 and 1980s, there is still a linear increase tendency in the number of published works. Understanding the mechanisms involved in the ability of these bacteria to promote growth in a wide broad of plant species under both laboratory and field conditions has been a preferential target for these published articles. This tendency could be considered a cause or consequence of the current increase in the number of commercial products formulated with Azospirillum around the world and a catalyzer for the increase of published articles along time.

The Singular Molecular Conformation of Humic Acids in Solution Influences Their Ability to Enhance Root Hydraulic Conductivity and Plant Growth.

Some studies have reported that the capacity of humic substances to improve plant growth is dependent on their ability to increase root hydraulic conductivity. It was proposed that this effect is directly related to the structural conformation in solution of these substances. To study this hypothesis, the effects on root hydraulic conductivity and growth of cucumber plants of a sedimentary humic acid and two polymers-polyacrylic acid and polyethylene glycol-presenting a molecular conformation in water solution different from that of the humic acid have been studied. The results show that whereas the humic acid caused an increase in root hydraulic conductivity and plant growth, both the polyacrylic acid and the polyethylene glycol did not modify plant growth and caused a decrease in root hydraulic conductivity. These results can be explained by the different molecular conformation in water solution of the three molecular systems. The relationships between these biological effects and the molecular conformation of the three molecular systems in water solution are discussed.

Correction to: Evaluation of growth and motility in non-photosynthetic Azospirillum brasilense exposed to red, blue, and white light.

In the original article, last name and first names of all the authors are inverted. The correct names should appears as "Romina Molina, Gastón López, Belén Rodríguez, Susana Rosas, Verónica Mora, Fabricio Cassán".

Co-treatment of an oily sludge and aged contaminated soil: permanganate oxidation followed by bioremediation.

The bioremediation of an oily sludge (321 ± 30 mg of polycyclic aromatic hydrocarbons/kgDRY SLUDGE and 13420 ± 1300 mg of aliphatic hydrocarbons/kgDRY SLUDGE) by mixture with contaminated soil (23 ± 2 mg of polycyclic aromatic hydrocarbons/kgDRY SOIL and 98 ± 10 mg of aliphatic hydrocarbons/kgDRY SOIL) was studied. Furthermore, the effect of oxidative pretreatments (persulfate and permanganate) on the performance of the global process was examined. The treatments reached contamination levels lower than the original residues, indicating the presence of synergic processes between a highly contaminated sludge and soil with a selected hydrocarbon-degrading community. Pretreatment with permanganate significantly improved biodegradation, possibly due to the increase in bioavailability and biodegradability of petroleum hydrocarbons. Two months of incubation was enough to reach the complete elimination of polycyclic aromatic hydrocarbons and 92% elimination of aliphatic hydrocarbons. Monitoring using five parameters (concentration of total petroleum hydrocarbons, total cultivable heterotrophic bacteria count, lipase and dehydrogenase activities, and polycyclic aromatic hydrocarbon-degrading bacteria count) as an approach for a preliminary scanning of the effectiveness of a treatment is proposed based on principal components analysis.

Desarrollo de marcadores moleculares del tipo SCAR para la identificación de Azospirillum brasilense Az39 / Development of sequence characterized amplified región markers for identification of Azospirillum brasilense Az39

Resumen Azospirillum brasilense Az39 es utilizada por empresas productoras de inoculantespara la formulación de bioinsumos en América del Sur desde hace más de 30 a˜nos. Esta cepapuede promover el crecimiento, desarrollo, así como la capacidad de tolerar diferentes tiposde estrés en las plantas inoculadas, lo que determina un aumento de la productividad de culti-vos de interés agronómico. En la actualidad, no existen protocolos en Argentina que permitanconfirmar la identidad de Az39 en productos comerciales a nivel de laboratorios de control decalidad de inoculantes. Por ello, el objetivo de este trabajo fue desarrollar una metodología enbase molecular que permita la identificación certera de A. brasilense Az39. Con la secuenciacompleta del genoma y mediante herramientas bioinformáticas, se pudieron reconocer frag-mentos de ADN presentes únicamente en el genoma de Az39. Se dise˜naron cebadores dirigidosa amplificar por PCR dichas secuencias. Como resultado se observaron los productos específicosúnicamente en la presencia de la cepa de interés. La reacción pudo detectar un título mínimode 105UFC/ml (4,5 ng/l ADN) o de 102UFC/ml (0,88 ng/l ADN) o una concentración mínimade 0,098 ng/l ADN, dependiendo del método de extracción utilizado. Los cebadores fueronevaluados en el análisis de productos comerciales obtenidos del mercado nacional, arrojandoresultados positivos, tanto en muestras directas como así también en pruebas confirmatoriasa partir de colonias aisladas de tales productos. La metodología desarrollada en este trabajo,permite la detección certera de A. brasilense Az39 en cultivos puros o mezclas complejas demicroorganismos.

Abstract Azospirillum brasilense Az39 has been used since more than 30 years by several companies in South America for biofertilizers production. This strain may promote plants growth and development, as well as the ability of inoculated plants to tolerate environmental stresses, which determines an increase in the productivity under field conditions. At present, there are no protocols in Argentina to confirm the identity of Az39 in commercial products; however, such biofertilizers are formulated almost exclusively with this strain. Therefore, the objective of this paper was to develop a molecular methodology that allows the accurate identification of A. brasilense Az39. Using the complete genome sequence and several bioinformatics tools, fragments of DNA present only in the Az39 genome were recognized. A set of PCR primers to amplify these sequences were designed, and the specific products were observed only in the strain of our interest. The sensitivity of the methodology was evaluated, where the strain could be detected up to a titer of 105 CFU/ml (4.5 ng/pl ADN) or 102 CFU/ml (0.88 ng/pl DNA) or in a minimal concentration of 0.098 ng/pl DNA, depending on the DNA extraction methodology used. Primers were tested against direct samples of commercial inoculants and cultures, in both cases there were specifics products, both in direct samples and in confirmatory tests from isolated colonies from those products. The procedure presented in this paper allows the accurate identification of A. brasilense Az39 in pure cultures, mixtures of microorganisms, and commercial biofertilizers.

[Development of sequence characterized amplified region markers for identification of Azospirillum brasilense Az39]. / Desarrollo de marcadores moleculares del tipo SCAR para la identificación de Azospirillum brasilense Az39.

Azospirillum brasilense Az39 has been used since more than 30 years by several companies in South America for biofertilizers production. This strain may promote plants growth and development, as well as the ability of inoculated plants to tolerate environmental stresses, which determines an increase in the productivity under field conditions. At present, there are no protocols in Argentina to confirm the identity of Az39 in commercial products; however, such biofertilizers are formulated almost exclusively with this strain. Therefore, the objective of this paper was to develop a molecular methodology that allows the accurate identification of A. brasilense Az39. Using the complete genome sequence and several bioinformatics tools, fragments of DNA present only in the Az39 genome were recognized. A set of PCR primers to amplify these sequences were designed, and the specific products were observed only in the strain of our interest. The sensitivity of the methodology was evaluated, where the strain could be detected up to a titer of 105 CFU/ml (4.5 ng/µl ADN) or 102 CFU/ml (0.88 ng/µl DNA) or in a minimal concentration of 0.098 ng/µl DNA, depending on the DNA extraction methodology used. Primers were tested against direct samples of commercial inoculants and cultures, in both cases there were specifics products, both in direct samples and in confirmatory tests from isolated colonies from those products. The procedure presented in this paper allows the accurate identification of A. brasilense Az39 in pure cultures, mixtures of microorganisms, and commercial biofertilizers.

Root ABA and H+-ATPase are key players in the root and shoot growth-promoting action of humic acids.

Although the ability of humic (HA) and fulvic acids (FA) to improve plant growth has been demonstrated, knowledge about the mechanisms responsible for the direct effects of HA and FA on the promotion of plant growth is scarce and fragmentary. Our study investigated the causal role of both root PM H+-ATPase activity and ABA in the SHA-promoting action on both root and shoot growth. The involvement of these processes in the regulation of shoot cytokinin concentration and activity was also studied. Our aim was to integrate such plant responses for providing new insights  to the current model on the mode of action of HA for promoting root and shoot growth. Experiments employing specific inhibitors and using Cucumis sativus L. plants show that both the root PM H+-ATPase activity and root ABA play a crucial role in the root growth-promoting action of SHA. With regard to the HA-promoting effects on shoot growth, two pathways of events triggered by the interaction of SHA with plant roots are essential for the increase in root PM H+-ATPase activity-which also mediates an increase in cytokinin concentration and action in the shoot-and the ABA-mediated increase in hydraulic conductivity (Lpr).

Regulation of IAA Biosynthesis in Azospirillum brasilense Under Environmental Stress Conditions.

Indole-3-acetic acid (IAA) is one of the most important molecules produced by Azospirillum sp., given that it affects plant growth and development. Azospirillum brasilense strains Sp245 and Az39 (pFAJ64) were pre-incubated in MMAB medium plus 100 mg/mL L-tryptophan and treated with or exposed to the following (a) abiotic and (b) biotic stress effectors: (a) 100 mM NaCl or Na2SO4, 4.0% (w/v) PEG6000, 0.5 mM H2O2, 0.1 mM abscisic acid, 0.1 mM 1-aminocyclopropane 1-carboxylic acid, 45 °C or daylight, and (b) 4.0% (v/v) filtered supernatant of Pseudomonas savastanoi (Ps) or Fusarium oxysporum (Fo), 0.1 mM salicylic acid (SA), 0.1 mM methyl jasmonic acid (MeJA), and 0.01% (w/v) chitosan (CH). After 30 and 120 min of incubation, biomass production, cell viability, IAA concentration (µg/mL), and ipdC gene expression were measured. Our results show that IAA production increases with daylight or in the presence of PEG6000, ABA, SA, CH, and Fo. On the contrary, exposure to 45 °C or treatment with H2O2, NaCl, Na2SO4, ACC, MeJA, and Ps decrease IAA biosynthesis. In this report, growth and IAA biosynthesis in A. brasilense under biotic and abiotic stress conditions are discussed from the point of view of their role in bacterial lifestyle and their potential application as bioproducts.

Shoot iron status and auxin are involved in iron deficiency-induced phytosiderophores release in wheat.

BACKGROUND: The release of phytosiderephores (PS) to the rhizosphere is the main root response to iron (Fe) deficiency in graminaceous plants. We have investigated the role of the Fe status in the shoot as well as of the signaling pathways controlled by three relevant phytoregulators - indolacetic acid (IAA), ethylene and nitric oxide (NO) - in the regulation of this root response in Fe-starved wheat plants. To this end, the PS accumulation in the nutrient solution and the root expression of the genes encoding the nicotianamine aminotransferase (TaNAAT) and ferritin (TaFER) have been evaluated in plants subjected to different treatments. RESULTS: The application of Fe to leaves of Fe-deficient plants prevented the increase in both PS root release and TaNAAT gene expression thus showing the relevant role of the shoot to root communication in the regulation of PS root release and some steps of PS biosynthesis. Experiments with specific hormone inhibitors showed that while ethylene and NO did not positively regulate Fe-deficiency induced PS root release, auxin plays an essential role in the regulation of this process. Moreover, the application of IAA to Fe-sufficient plants promoted both PS root release and TaNAAT gene expression thus indicating that auxin might be involved in the shoot to root signaling network regulating Fe-deficiency root responses in wheat. CONCLUSIONS: These results therefore indicate that PS root release in Fe-deficient wheat plants is directly modulated by the shoot Fe status through signaling pathways involving, among other possible effectors, auxin.

Efficiency of surfactant-enhanced bioremediation of aged polycyclic aromatic hydrocarbon-contaminated soil: Link with bioavailability and the dynamics of the bacterial community.

Shifts in the bacterial-community dynamics, bioavailability, and biodegradation of polycyclic aromatic hydrocarbons (PAHs) of chronically contaminated soil were analyzed in Triton X-100-treated microcosms at the critical micelle concentration (T-CMC) and at two sub-CMC doses. Only the sub-CMC-dose microcosms reached sorbed-PAH concentrations significantly lower than the control: 166±32 and 135±4mgkg-1 dry soil versus 266±51mgkg-1; consequently an increase in high- and low-molecular-weight PAHs biodegradation was observed. After 63days of incubation pyrosequencing data evidenced differences in diversity and composition between the surfactant-modified microcosms and the control, with those with sub-CMC doses containing a predominance of the orders Sphingomonadales, Acidobacteriales, and Gemmatimonadales (groups of known PAHs-degrading capability). The T-CMC microcosm exhibited a lower richness and diversity index with a marked predominance of the order Xanthomonadales, mainly represented by the Stenotrophomonas genus, a PAHs- and Triton X-100-degrading bacterium. In the T-CMC microcosm, whereas the initial surface tension was 35mNm-1, after 63days of incubation an increase up to 40mNm-1 was registered. The previous observation and the gas-chromatography data indicated that the surfactant may have been degraded at the CMC by a highly selective bacterial community with a consequent negative impact on PAHs biodegradation. This work obtained strong evidence for the involvement of physicochemical and biologic influences determining the different behaviors of the studied microcosms. The results reported here contribute significantly to an optimization of, surfactant-enhanced bioremediation strategies for chronically contaminated soil since the application of doses below the CMC would reduce the overall costs.

Strategies for oxidation of PAHs in aged contaminated soil by batch reactors.

Polycyclic aromatic hydrocarbons (PAH) are neutral, nonpolar and hydrophobic molecules that tend to sorb onto soil organic matter. Chemical oxidation is a good choice to avoid the limitations of bioremediation. To evaluate the efficiency of different types of oxidation (permanganate, hydrogen peroxide, and persulfate) and activation (heat, alkaline, and iron), batch reactors were prepared. The soil was contaminated with phenanthrene and pyrene (1200 ± 200 and 2800 ± 100mg per kg of dry soil, respectively) and aged for fifteen months. Treatments were prepared with 10g of contaminated dry soil and 20ml of water and incubated at room temperature for 7 days. Analyses of phenanthrene and pyrene concentrations, soil pH and electric conductivity were performed. Counts of heterotrophic cultivable bacteria on R2A medium and PAH-degraders were carried out after 7 days of treatment. The persulfate treatment at room temperature, without the addition of activators, achieved better results than treatments with the same doses of permanganate or hydrogen peroxide. All the strategies to improve persulfate treatments yielded higher degradation of pyrene than the biological control, as expected from the structural description of this compound by Clar's model. The thermal activation of persulfate (65°C for 6h) led to the degradation of more than 90% of both PAHs after 7 days of treatment.

Involvement of Hormone- and ROS-Signaling Pathways in the Beneficial Action of Humic Substances on Plants Growing under Normal and Stressing Conditions.

The importance of soil humus in soil fertility has been well established many years ago. However, the knowledge about the whole mechanisms by which humic molecules in the rhizosphere improve plant growth remains partial and rather fragmentary. In this review we discuss the relationships between two main signaling pathway families that are affected by humic substances within the plant: one directly related to hormonal action and the other related to reactive oxygen species (ROS). In this sense, our aims are to try the integration of all these events in a more comprehensive model and underline some points in the model that remain unclear and deserve further research.

Root-Shoot Signaling crosstalk involved in the shoot growth promoting action of rhizospheric humic acids.

Numerous studies have shown the ability of humic substances to improve plant development. This action is normally reflected in an enhancement of crop yields and quality. However, the mechanisms responsible for this action of humic substances remain rather unknown. Our studies have shown that the shoot promoting action of sedimentary humic acids is dependent of its ability to increase root hydraulic conductivity through signaling pathways related to ABA, which in turn is affected in roots by humic acids in an IAA-NO dependent way. Furthermore, these studies also indicate that the primary action of humic acids in roots might also be physical, resulting from a transient mild stress caused by humic acids associated with a fouling-cleaning cycle of wall cell pores. Finally the role of alternative signal molecules, such as ROS, and corresponding signaling pathways are also discussed and modeled in the context of the above-mentioned framework.

Abscisic Acid Regulation of Root Hydraulic Conductivity and Aquaporin Gene Expression Is Crucial to the Plant Shoot Growth Enhancement Caused by Rhizosphere Humic Acids.

The physiological and metabolic mechanisms behind the humic acid-mediated plant growth enhancement are discussed in detail. Experiments using cucumber (Cucumis sativus) plants show that the shoot growth enhancement caused by a structurally well-characterized humic acid with sedimentary origin is functionally associated with significant increases in abscisic acid (ABA) root concentration and root hydraulic conductivity. Complementary experiments involving a blocking agent of cell wall pores and water root transport (polyethylenglycol) show that increases in root hydraulic conductivity are essential in the shoot growth-promoting action of the model humic acid. Further experiments involving an inhibitor of ABA biosynthesis in root and shoot (fluridone) show that the humic acid-mediated enhancement of both root hydraulic conductivity and shoot growth depended on ABA signaling pathways. These experiments also show that a significant increase in the gene expression of the main root plasma membrane aquaporins is associated with the increase of root hydraulic conductivity caused by the model humic acid. Finally, experimental data suggest that all of these actions of model humic acid on root functionality, which are linked to its beneficial action on plant shoot growth, are likely related to the conformational structure of humic acid in solution and its interaction with the cell wall at the root surface.

Remediation of phenanthrene-contaminated soil by simultaneous persulfate chemical oxidation and biodegradation processes.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous compounds with carcinogenic and/or mutagenic potential. To address the limitations of individual remediation techniques and to achieve better PAH removal efficiencies, the combination of chemical and biological treatments can be used. The degradation of phenanthrene (chosen as a model of PAH) by persulfate in freshly contaminated soil microcosms was studied to assess its impact on the biodegradation process and on soil properties. Soil microcosms contaminated with 140 mg/kgDRY SOIL of phenanthrene were treated with different persulfate (PS) concentrations 0.86-41.7 g/kgDRY SOIL and incubated for 28 days. Analyses of phenanthrene and persulfate concentrations and soil pH were performed. Cultivable heterotrophic bacterial count was carried out after 28 days of treatment. Genetic diversity analysis of the soil microcosm bacterial community was performed by PCR amplification of bacterial 16S rDNA fragments followed by denaturing gradient gel electrophoresis (DGGE). The addition of PS in low concentrations could be an interesting biostimulatory strategy that managed to shorten the lag phase of the phenanthrene biological elimination, without negative effects on the physicochemical and biological soil properties, improving the remediation treatment.

Tumor del estroma gastrointestinal y resolución laparoscópica: a propósito de un caso / Gastrointestinal tumor laparoscopic resolution: a case report

Paciente femenina 80 años acude por presentar epigastralgia, pirosis de 2 meses de evolución, se realiza endoscopia superior evidenciando lesión con compresión extrínseca en curvatura menor del estómago, biopsia negativa para malignidad, tomografía de abdomen y pelvis: tumor de 5 cm en curvatura y epiplón menor, eco endoscopia con punción: tumor que afecta pared muscular gástrica sin afección de mucosa sin extensión a órganos vecinos, punción: lesión fusocelular benigna, se plantea diagnóstico leiomioma vs. tumor del estroma gastrointestinal gástrico; se practica gastrectomía parcial vertical laparoscópica, márgenes macroscópicos negativos, evolución posoperatoria satisfactoria; biopsia definitiva: tumor del estroma gastrointestinal gástrico de bajo riesgo márgenes de 1 cm libres, valoración conjunta con medicina oncológica se decide en vista de las características biológicas resección quirúrgica completa, y edad de la paciente no amerita tratamiento adyuvante por lo que se mantiene en observación. La resección laparoscópica en el tratamiento de estos tumores gástricos es efectiva

Feminine patient 80 years present epigastralgia and pirosis 2 months of evolution, superior endoscopy is don edemonstrating an extrinsic lesion with compression in smaller curvature of stomach, whose negative biopsy for malignity, tomography of abdomen and pelvis reports 5 cm approximately tumor in smaller curvature and epiplon, endoscopic ultrasound with puncture reports: gastric muscular wall tumor without affection of mucosa without neighboring organ extension affects, and puncture injury:fusocelular benign, reason we considers: gastric diagnosis leiomioma vs. gastrointestinal stomach tumor; is taken a laparoscopic vertical partial gastrectomy, with margins macroscopic negatives, with satisfactory evolution post operating, definitive biopsy reports: tumor low risk with free margins of 1 cm; because for a complete surgical resection, in evaluation with oncologic medicine, decided in view of characteristics and age of the patient does not deserve adjuvant treatment reason why she stays in observation. Laparoscopic resection on this stomach tumor it’s an effective treatment

Adrenalectomía laparoscópica en Adenoma virilizante a propósito de un caso / Laparoscopy adrenalectomy in virilizant adenoma: a case report

Presentar un caso clínico. Paciente femenina de 40 años de edad IIIG IIIP enfermedad actual en 2007 con amenorrea, signos de virilización, fascie cushinoide, por lo cual acude a facultativo. Estudia con un perfil hormonal reportando en abril de 2009: prolactina 7,83, T3, T4, TSH sin alteraciones, estradiol elevado 280, progesterona en 0,4, FSH 9,7 LH 6,5, ultrasonido abdominopélvico reportando quiste de ovario izquierdo simple de 36 mm x 33 mm x 28 mm, volumen de 17,5 cm³, TAC abdomino-pélvica reporta imagen heterogénea capta contraste, contornos definidos en fosa suprarrenal derecha 4,8 cm de diámetro, sugestiva de adenoma suprarrenal, se aprecian aumento de volumen uterino sugestivo de fibromatosis y quiste de ovario derecho simple, catecolaminas urinarias y ácido vanidilmandélico normales, se decide tomar conducta quirúrgica definitiva, por lo que se solicita pre operatorio y el 17-02-10 fue llevada a adrenalectomía laparoscópica, con diagnóstico de adenoma suprarrenal virilizante. La biopsia definitiva reportó tumor epitelial benigno de células corticales adrenales (Adenoma adrenal cortical), sin invasión capsular necrosis ni pleomorfismos sin indicios de malignidad. La paciente fue dada de alta a las 24 horas, con posoperatorio inmediato satisfactorio, Presentando sangrado menstrual 1 mes posterior a la cirugía y reversión posquirúrgico de los signos de virilización. Los adenomas suprarrenales virilizantes son una patología rara pero cuando se presenta la clínica es inequívoca, se recomienda el abordaje laparoscópica de estas lesiones en pacientes bien seleccionados ya que el beneficio es indiscutible

Present a clinical case. Feminine of 40 years old IIIG IIIP initial start disease in 2007 with amenorrhoea, virilization signs, cushin fascies. Goes to facultative that studies with hormonal profile reporting in April of 2009: Prolactin 7.83, T3 T4 TSH without alterations, estradiol 280, progesterone in 0,4, FSH 9.7 LH 6.5, pelvic and abdominal ultrasound reporting cyst simple left ovary of 36 mm x33 mm x 28 mm and volume of 17.5 cm³, abdominal and pelvic TAC that reports heterogeneous image that catches contrast, contours defined in right adrenal grave 4.8 cm of diameter, suggestive of adrenal adenoma, also increase uterine volume of fibromatosis and cyst of straight simple ovary, urinary catecholamines and normal vanidilmandelic acid are appraised, reason by which it is decided to take definitive surgical treatment, reason why asks for pre operating studies and the 02-17-10 was taken to laparoscopic adrenectomy, with diagnosis of virilizant adrenal adenoma. The definitive biopsy report benign epithelial tumor of adrenal cortical cells (cortical adrenal adenoma), without capsular invasion necrosis non pleomorphic, without malignant suspicious items. The patient egresses to the 24 hours after surgery, with an immediate satisfactory post-operative, Presenting/displaying menstrual bleeding 1 month subsequent to the surgery and postsurgical reversion of the signs of virilization. The virilizant adrenal adenomas are a rare pathology but when the clinic appears is unequivocal, laparoscopic boarding of these injuries in selected patients is good recommended since the benefit is unquestionable

Phenol depletion by thermally activated peroxydisulfate at 70°C.

The ability of thermal activated peroxydisulfate (PS) of mineralizing phenol at 70°C from contaminated waters is investigated. Phenol in concentrations of 10(-4) to 5×10(-4)M is quantitatively depleted by 5×10(-3) to 10(-2)M activated PS in 15 min of reaction. However, mineralization of the organic carbon is not observed. Instead, an insoluble phenol polymer-type product is formed. A reaction mechanism including the formation of phenoxyl radicals and validated by computer simulations is proposed. High molecular weight phenolic products are formed by phenoxyl radical H-abstraction reactions. This is not the case for the room temperature degradation of phenol by sulfate radicals where sulfate addition to the aromatic ring mainly leads to the generation of hydroxycyclohexadienyl radicals leading to hydroxybenzenes and oxidized open chain products. Therefore, a change in the reaction mechanism is observed with increasing temperature, and thermal activation of PS at 70°C does not lead to the mineralization of phenol. Thus PS activation at 70°C may be considered a potential method to reduce the load of phenol in polluted waters by polymerization.

Auxin: a major player in the shoot-to-root regulation of root Fe-stress physiological responses to Fe deficiency in cucumber plants.

The aim of this study was to investigate the effects of IAA and ABA in the shoot-to-root regulation of the expression of the main Fe-stress physiological root responses in cucumber plants subjected to shoot Fe functional deficiency. Changes in the expression of the genes CsFRO1, CsIRT1, CsHA1 and CsHA2 (coding for Fe(III)-chelate reductase (FCR), the Fe(II) transporter and H+-ATPase, respectively) and in the enzyme activity of FCR and the acidification capacity were measured. We studied first the ability of exogenous applications of IAA and ABA to induce these Fe-stress root responses in plants grown in Fe-sufficient conditions. The results showed that IAA was able to activate these responses at the transcriptional and functional levels, whereas the results with ABA were less conclusive. Thereafter, we explored the role of IAA in plants with or without shoot Fe functional deficiency in the presence of two types of IAA inhibitors, affecting either IAA polar transport (TIBA) or IAA functionality (PCIB). The results showed that IAA is involved in the regulation at the transcriptional and functional levels of both Fe root acquisition (FCR, Fe(II) transport) and rhizosphere acidification (H+-ATPase), although through different, and probably complementary, mechanisms. These results suggest that IAA is involved in the shoot-to-root regulation of the expression of Fe-stress physiological root responses.