Tirame no ambiente: efeito de substâncias húmicas e iões Cu(II)

Doutoramento em QuímicaEm Portugal, o tirame é um dos fungicidas mais utilizados, cujas vendas aumentaram significativamente nos últimos anos, sendo também um dos fungicidas mais utilizados em todo o mundo. No entanto, em comparação com outros pesticidas, existe falta de informação na literatura sobre o seu comportamento em sistemas ambientais, nomeadamente, no que diz respeito à sua degradação no solo ou em águas e produtos a que dá origem. Neste contexto, o objetivo deste trabalho foi estudar a influência das substâncias húmicas e iões cobre no comportamento e destino do tirame no meio ambiente. Foram realizados vários estudos para analisar o comportamento do tirame em solos com diferentes conteúdos de matéria orgânica e de iões cobre, e em águas naturais, estudando como as substâncias húmicas, os iões cobre e a luz solar podem afetar a sua degradação. Os estudos de adsorção-desadsorção do tirame nos solos revelaram que a matéria orgânica do solo e o conteúdo de cobre afetavam os processos de adsorção-desadsorção do tirame, influenciando a sua lixiviação e persistência no solo. De facto, verificou-se que o teor de cobre do solo tinha um efeito bastante marcante no processo de adsorçãodesadsorção do tirame. Verificou-se a ocorrência de reações entre o tirame e os iões cobre, cuja extensão durante os estudos de adsorção pode ser fortemente dependente do teor de cobre do solo e da concentração inicial de tirame em solução. Assim, a escolha do tempo de equilíbrio em estudos de adsorção e a determinação das isotérmicas de adsorção ao solo torna-se uma tarefa difícil. Além disso, os complexos formados com o cobre existente no solo são persistentes, não sendo facilmente lixiviados para as águas subterrâneas. Conclui-se que os iões cobre(II) podem contribuir para a imobilização do tirame no solo e o aumento da persistência dos seus resíduos ligados ao cobre. A partir de estudos de recuperação do tirame em águas naturais verificou-se a ocorrência de uma rápida degradação do tirame, devido provavelmente aos iões metálicos, nomeadamente, iões cobre. Verificou-se que dependendo da razão tirame:Cu podiam ocorrer dois processos: (i) complexação entre o tirame e o cobre, quando não há excesso de iões cobre, sendo o complexo formado mais persistente que o tirame; (ii) ou, quando há um grande excesso de iões cobre, a degradação do tirame e a estabilização dos produtos de degradação por complexação, podendo formar-se complexos que permanecem sem alteração em solução durante pelo menos dois meses. No geral, foi possível, pela primeira vez, identificar alguns dos complexos de cobre formados ao longo do tempo. Por fim, estudou-se a cinética de fotodegradação do tirame em solução aquosa sob a ação da luz solar e identificaram-se, pela primeira vez, três fotoprodutos. Verificou-se um aumento da velocidade de fotodegradação do tirame na presença de substâncias húmicas. Assim, podemos concluir que a matéria orgânica, os iões cobre(II) e a luz solar têm um efeito importante no comportamento do tirame no meio ambiente. Contudo, os iões cobre têm um efeito mais marcante na degradação e persistência dos produtos que são formados.In Portugal thiram is one of the most used fungicides, whose sales have increased significantly along the years and it is also one of the most used fungicides all over the world. However, comparing to other pesticides, there is a lack of information in the literature about the behaviour of thiram in environmental systems, namely, in what concerns its degradation in soil or in water systems and products formed. In this context, the aim of this work was to assess the influence of humic substances and copper ions on the behaviour and fate of thiram in the environment. Different studies were performed to assess the behaviour of thiram in soils, with different organic amendments and with different copper contents, and in natural water, studding how humic substances, copper ions and sunlight can affect its degradation. Adsorption-desorption studies of thiram onto soil revealed that organic mater and soil copper contents affect thiram adsorption-desorption processes, influencing its leachability and persistence in soil. In fact, soil copper content has a marked effect on the sorption process of thiram onto soil. Reactions between thiram and copper ions occur and the extent of their occurrence during adsorption studies may be strongly dependent on the soil copper content and on the initial thiram concentration in solution making the choice of the equilibration time for batch sorption studies and adsorption isotherms determination a difficult task. The complexes formed with copper in soil are persistent, and they are not easily leached from soil to groundwater. Thus, we can conclude that copper may contribute to the immobilization of thiram in soil. Thiram recovery from natural waters showed rapid thiram degradation in environmental matrices, probably due to metal ions, namely copper. Depending on the Thi:Cu ratio two processes can occur: (i) when there is no excess of copper ions there will be the complexation between thiram and copper ions and the complex formed is more persistence than thiram; (ii) in the presence of a large excess of copper ions, which is the more probable situation in natural waters, thiram degradation can occur and then the degradation products are stabilized by complexation, forming complexes which can persist in aqueous solutions for at least two months. It was possible, by the first time, to identify some copper complexes formed. The kinetics of the photodegradation of thiram in aqueous solutions, under sunlight, was studied and three photodegradation products were identified for the first time. Besides, it was shown that humic substances enhance the thiram photodegradation rate. Thus, we can conclude from this work that the organic matter, copper ions and sunlight have important effects on the behaviour and fate of thiram in the environment. However it should be highlighted that copper ions have an extremely marked effect on the degradation of thiram and persistence of products which are formed

Pesticides in the Modern World

The introduction of the synthetic organochlorine, organophosphate, carbamate and pyrethroid pesticides by 1950's marked the beginning of the modern pesticides era and a new stage in the agriculture development. Evolved from the chemicals designed originally as warfare agents, the synthetic pesticides demonstrated a high effectiveness in preventing, destroying or controlling any pest. Therefore, their application in the agriculture practices made it possible enhancing crops and livestock's yields and obtaining higher-quality products, to satisfy the food demand of the continuously rising world's population. Nevertheless, the increase of the pesticide use estimated to 2.5 million tons annually worldwide since 1950., created a number of public and environment concerns. This book, organized in two sections, addresses the various aspects of the pesticides exposure and the related health effects. It offers a large amount of practical information to the professionals interested in pesticides issues

Twenty-fourth Illinois Custom Spray Operators' Training School: summaries of presentations

Illinois Custom Spray Operators' School Summaries of Presentations. January 26-27, 1972. In cooperation with University of Illinois College of Agriculture, Agricultural Extension Service, and the Illinois Natural History Survey. Program planning with the assistance of officers of the Illinois Association of Aerial Applicators and the Illinois Agricultural Spraying Association

Twenty-third Illinois Custom Spray Operators' Training School: summaries of presentations

Illinois Custom Spray Operators' School Summaries of Presentations. January 27-28, 1971. In cooperation with University of Illinois College of Agriculture, Agricultural Extension Service, and the Illinois Natural History Survey. Program planning with the assistance of officers of the Illinois Association of Aerial Applicators and the Illinois Agricultural Spraying Association

Breeding for microbiome-mediated disease resistance

Plant-associated microbial communities play a crucial role for the expression of various plant traits including disease resistance. Increasing evidence suggests that host genotype influences the composition and function of certain microbial key groups, which, in turn, effects how the plant reacts to environmental stresses. Several studies indicate that modern plant breeding may have selected against plant traits essential for hosting and supporting beneficial microbes. However, they also highlight the presence of an exploitable genetic base for the regulation of the rhizosphere microbiota. We illustrate the concept of breeding for microbial symbioses with pea (Pisum sativum L.). Firstly, genotypic variation for the efficiency of a mycorrhizal symbiosis is shown, as measured by an estimation of the plant benefit per symbiotic unit. Secondly, we extend the view towards the wider fungal community using ITS amplicon sequencing. Two pea genotypes with contrasting resistance levels against pathogen complexes are investigated to provide information on the functional diversity of the rhizosphere microbiome in a naturally infested agricultural soil. In the near future, microbial hubs and diversity indices will be linked with root exudation in order to elucidate the plant’s capacity to influence the microbial composition leading to disease susceptibility or resistance. Current and future research activities of our group aim to make use of plant-microbiome interactions to develop advanced screening tools for breeders for an improved expression and stability of important plant traits

Bioeffector products for plant growth promotion in agriculture : modes of action and the application in the field

Modern agriculture faces a conflict between sustainability and the demand for a higher food production. This conflict is exacerbated by climate change and its influence on vegetation, ecology and human society. To reduce land use, the reduction of yield losses and food waste is crucial. Moreover a sustainable intensification is necessary to increase yields, while at the same time input of limited resources such as drinking water or fertilizer should be kept as low as possible. This might be achieved by improving nutrient recycling and plant resistance to abiotic or biotic stress. Bioeffectors (BE) comprise seaweed or plant extracts and microbial inoculums that may stimulate plant growth by phytohormonal changes and increase plant tolerance to abiotic stress (biostimulants), solubilize or mobilize phosphorus from sparingly soluble sources such as Al/Fe or Ca-phosphates in the soil, rock phosphates, recycling fertilizer or organic phosphorus sources like phytate (biofertilizer), or improve plant resistance against pathogens by induced-systemic resistance (ISR) or antibiosis (biocontrol). For this study, in total 18 BE products were tested in germination, pot and field experiments for their potential to improve plant growth, cold stress tolerance, nutrient acquisition and yield in maize and tomato. Additionally, a gene expression analysis in maize was performed using whole transcriptome sequencing (RNA-Seq) after the application of two potential plant growth promoting rhizobacteria (PGPR), the Pseudomonas sp. strain DSMZ 13134 Proradix and the Bacillus amyloliquefaciens strain FZB42. Seaweed products supplemented with high amounts of the micronutrients Zn and Mn were effective in reducing detrimental cold stress reactions in maize whereas microbial products and seaweed extracts without micronutrient supplementation failed under the experimental conditions. At optimal temperature the product containing the Pseudomonas sp. strain was repeatedly able to stimulate root and shoot growth of maize plants whereas in tomato only in heat-treated soil substrate significant effects were observed. Results indicate that the efficacy of the product was mainly attributed to stimulation or shifts in the soil microbial community. Additionally, the FZB42 strain was able to stimulate root and plant growth in some experiments whereas the effects were less reproducible and more sensitive to environmental conditions. Fungal BE products were less effective in plant growth stimulation and showed detrimental effects in some experiments. Under the applied experimental conditions BE-derived plant growth stimulation mainly was attributed to biostimulation but aspects of biofertilization or biocontrol cannot be excluded, as all experiments were conducted in non-sterile soil substrates. Root and shoot growth are stimulated in response to hormonal shifts. In the gene expression analysis only weak responses to BE treatments were observed, as previously reported from other studies conducted under non-sterile conditions. Nevertheless, some plant stress responses were observed that resembled in some aspects those reported for phosphorus (P) deficiency in others those reported for ISR/SAR. Especially the activation of plant defence mechanisms, such as the production of secondary metabolites, ethylene production and reception and the expression of several classes of stress-related transcription factors, including JA-responsive JAZ genes, was observed. It also seems probable that in plants growing in PGPR-drenched soils, especially at high application rates, a sink stimulation for assimilates triggers changes in photosynthetic activity and root growth leading to an improved nutrient acquisition. Nevertheless, due to the complexity of interactions in natural soil environments as well as under practice conditions, a designation of a distinct mode of action for plant growth stimulation by microbial BEs is not realistic. A comparison of the overall results with those reported in literature or other working groups in a common research project (Biofector) supported the often-reported low reproducibility of plant growth promotion effects by BE products under applied conditions. Factors that influenced BE efficacy were application time and rates, temperature, soil buffer capacity, phosphorus sources and nitrogen fertilization, light conditions and the soil microbial community. Results indicate that in maize cultivation seed treatment is the most economic application technique for microbial products whereas for vegetable or high-value crops with good economic benefit soil drenching is recommended. For seaweed extracts foliar application seems to be the most economic and efficient choice. Furthermore, results emphasize the importance of a balanced natural soil microflora for plant health and yield stability.Die moderne Landwirtschaft steht vor einem Konflikt zwischen Nachhaltigkeit und der Forderung nach einer höheren Nahrungsmittelproduktion. Der Einsatz begrenzter Ressourcen wie Trinkwasser sowie umweltschädlicher Stoffe (Düngemittel, Pestizide) sollte so gering wie möglich gehalten werden. Dies kann durch Verbesserungen im Nährstoffrecycling sowie durch Stärkung der Pflanzenresistenz gegenüber abiotischem oder biotischem Stress erreicht werden. Bio-Effektoren (BE) umfassen Algen- oder Pflanzenextrakte und mikrobielle Inokula, die das Pflanzenwachstum durch phytohormonelle Veränderungen stimulieren und die Pflanzenverträglichkeit gegenüber abiotischem Stress erhöhen (Biostimulanzien), Phosphor aus schwerlöslichen Quellen wie Al/Fe oder Ca-Phosphaten im Boden, Steinphosphaten, Recyclingdüngern oder organischen Phosphorquellen wie Phytat mobilisieren (Bio-Dünger) oder zur Verbesserung der Pflanzenresistenz gegen Pathogene durch induzierte systemische Resistenz (ISR) oder Antibiose (Bio-Pestizide) beitragen. Insgesamt wurden 18 BE-Produkte in Keimungs-, Topf- und Feldexperimenten auf ihr Potenzial zur Verbesserung des Pflanzenwachstums, der Kältestresstoleranz, der Nährstoffaufnahme und des Ertrags in Mais und Tomate getestet. Zusätzlich wurde eine Genexpressionsanalyse in Mais durchgeführt unter Verwendung der vollständigen Transkriptomsequenzierung (RNA-Seq) nach der Anwendung von zwei potentiell pflanzenwachstumsfördernden Rhizobakterien (PGPR), dem Pseudomonas sp. Stamm DSMZ 13134 "Proradix" und dem Bacillus amyloliquefaciens Stamm FZB42. Meeresalgenprodukte, die mit hohen Mengen der Mikronährstoffe Zn und Mn angereichert wurden, konnten Kältestressreaktionen bei Mais wirksam reduzieren, während mikrobielle Produkte und Meeresalgenextrakte ohne Mikronährstoffergänzung unter den Testbedingungen erfolglos waren. Bei optimaler Temperatur war das Produkt, das den Pseudomonas-Stamm enthält, wiederholt in der Lage, Wurzel- und Sprosswachstum von Maispflanzen zu stimulieren, während in Tomaten nur in wärmebehandeltem Bodensubstrat signifikante Effekte beobachtet wurden. Die Ergebnisse legen nahe, dass die Wirksamkeit des Produkts hauptsächlich auf Stimulation oder Veränderungen in der mikrobiellen Gemeinschaft im Boden zurückzuführen ist. Auch der FZB42-Stamm war in der Lage, das Wachstum von Wurzeln und Pflanzen in einigen Experimenten zu stimulieren, während die Effekte weniger reproduzierbar und empfindlicher für Umweltbedingungen waren. Pilzliche BE-Produkte waren bei der Pflanzenwachstumsstimulation weniger effizient und zeigten in einigen Experimenten auch schädliche Wirkungen. Unter den angewandten experimentellen Bedingungen scheint die BE-abgeleitete Pflanzenwachstumsstimulation hauptsächlich auf Biostimulation zurückzuführen zu sein, aber Aspekte der Bio-Düngung oder Bio-Kontrolle können nicht ausgeschlossen werden, da alle Experimente in nicht-sterilen Bodensubstraten durchgeführt wurden. Die Stimulation des Wurzelwachstums und der Sprosswachstumsrate ist eine Reaktion auf hormonelle Veränderungen. Die Genexpression zeigte nur schwache Reaktionen auf die BE-Behandlungen, wie bereits aus anderen Studien unter nicht-sterilen Bedingungen berichtet wurde. Trotzdem wurden einige pflanzliche Stressreaktionen beobachtet, die entweder für Phosphor (P)-Mangel oder aber ISR / SAR als typisch gelten. Insbesondere die Aktivierung von Abwehrmechanismen wie die Produktion von Sekundärmetaboliten, die Ethylenproduktion und -rezeption sowie die Expression mehrerer Klassen stressbedingter Transkriptionsfaktoren, einschließlich JA-responsiver JAZ-Gene, wurde beobachtet. Es scheint auch wahrscheinlich, dass in Pflanzen, die in PGPR-durchtränkten Böden wachsen, insbesondere bei hohen Aufwandmengen, eine Senkenstimulation für Assimilate die Photosyntheserate erhöht sowie Veränderungen im Wurzelwachstum auslöst, die zu einer verbesserten Nährstoffaufnahme führen können. Die Bestimmung eines speziellen Wirkungs-mechanismus ist jedoch durch die Komplexität der Interaktionen im Boden nicht möglich. Ein Vergleich der Gesamtergebnisse mit denen, die in der Literatur oder anderen Arbeitsgruppen berichtet wurden, unterstützt die oft berichtete geringe Reproduzierbarkeit von Pflanzenwachstumseffekten durch BE-Produkte unter Praxisbedingungen. Faktoren, die die BE-Wirksamkeit beeinflussen, sind Applikationszeit und -rate, Temperatur, Bodenpufferkapazität, Phosphor-Quelle, Stickstoff-Düngung, Lichtbedingungen sowie die mikrobielle Gemeinschaft des Bodens. Die Ergebnisse zeigen zudem, dass Saatgutbehandlung die wirtschaftlichste Anwendungstechnik für mikrobielle Produkte im Maisanbau ist, wobei für hochpreisige Kulturen im Gemüsebau konzentrierte Bodenapplikation empfohlen ist. Für Algenextrakte scheint Blattapplikation die beste Wahl zu sein. Die Ergebnisse zeigen zudem, wie wichtig eine ausgewogene, natürliche Bodenmikroflora für die Pflanzengesundheit und Ertragsstabilität ist