Caractérisation des substances humiques biomimétiques : effets sur les végétaux

Présentes dans tous les écosystèmes, les substances humiques sont les constituants majeurs de la matière organique. Dans les sols, ces molécules possèdent des effets positifs sur la croissance et le développement des plantes. Cependant, la composition et les propriétés des substances humiques varient selon l'origine et leurs conditions de formation. La transformation physico-chimique d'une matière première végétale homogène permet de préparer des produits de composition stable et reproductible, les substances humiques biomimétiques (SHB), comparables aux substances humiques naturelles. Les objectifs de ce travail visent, d'une part, à déterminer la composition et l'origine des substances humiques biomimétiques à travers leurs caractérisations chimiques; et d'autre part, à évaluer l'efficacité de ces produits sur la croissance et le développement des plantes (pélargonium, maïs) cultivées en culture hors-sol. L'analyse chimique des produits obtenus montre que les substances humiques biomimétiques possèdent les mêmes propriétés que les substances humiques naturelles. Elles sont composées de 60% d'acides humiques dérivés principalement de la lignine et de 40% d'acides fulviques provenant de la cellulose et de l'hémicellulose. L'application de substances humiques biomimétiques induit des effets positifs sur les végétaux pour une dose optimale de 50 mg.L-1 de carbone. La germination et la rhizogenèse du maïs sont stimulées en présence d'extraits humiques. Les effets des substances humiques biomimétiques se traduisent également par la stimulation de la mise à fleur du pélargonium et l'accélération des phases végétatives du maïs. Ces produits semblent agir sur la vitesse des mécanismes de croissance. L'ajout du produit permet aux plants de maïs de réaliser une économie d'eau en réduisant leur consommation. De plus, les acides fulviques semblent plus efficaces que les acides humiques. Ce travail précise l'intérêt des substances humiques biomimétiques et permet d'envisager leur application dans les domaines horticole et agricole. ABSTRACT : Present in all the ecosystems, humic substances are the major components of organic matter. In soils, these molecules have some positive effects on growth and plant development. However, the composition and the properties of humic substances vary according to the origin and their conditions of formation. The physico-chemical transformation of homogeneous plant raw material allows to prepare stable humic products with a reproducible composition, the biomimetic humic substances (BSH), which are comparable to natural compounds. This work deals with, on one hand, the determination of composition and origins of the biomimetic humic substances through their chemical characterizations; and on the other hand, the evaluation of their efficiency on growth and plant development (pelargonium, maize) cultivated in hydroponic culture. Chemical analysis of the products shows that the biomimetic humic substances present the same properties as the natural humic substances. They are composed of 60% of humic acids, derived from lignin and 40% of fulvic acids, coming from cellulose and hemicellulose. Biomimetic humic substances induces positive effects on the plants tested, for an optimal concentration of 50 mg.L-1 of carbon. The germination and rhizogenese of maize are stimulated in the presence of humic extracts. The effects of biomimetic humic substances also implies the stimulation of pelargonium flowering and the acceleration of vegetative phases of maize. These products seem to act on the speed of the plant growth mechanisms. The biomimetic humic substances supply induces a water economy by reducing water consumption of maize crop, and fulvic acids seem to be more effective than humic acids. This work specifies the special interests of biomimetic humic substances, particularly concerning their possible application in horticultural and agricultural fields

Effects of humic substances derived from organic waste enhancement on the growth and mineral nutrition of maize

A physico-chemical process has been developed to transform and enhance lignocellulosic waste in liquid humic extracts: humic-like substances (HLS). The aim of this study was to determine the effects of HLS on plant physiology in order to consider their agricultural use as organic fertilizers. The effects of HLS were evaluated on maize seed germination, and their impact on growth, development and mineral nutrition was studied on maize plants cultivated under hydroponic conditions. The experimental results showed that HLS do not increase the percentage and rate of germination but enhance the root elongation of seeds thus treated. Positive effects were also observed on the whole plant growth as well as on root, shoot and leaf biomass. These effects can be related to the high water and mineral consumption of plants undergoing this treatment. The high water efficiency indicated that such plants produce more biomass than non-treated plants for the same consumption of the nutrient solution. Furthermore, the use of HLS induced a flowering precocity and modified root development suggesting a possible interaction of HLS with developmental processes. Considering the beneficial effect of HLS on different stages of plant growth, their use may present various scientific and economic advantages. The physico-chemical transformation of sawdust is an interesting way of enhancing organic waste materials

Grape marc extract acts as elicitor of plant defence responses

International audiencePlant protection based on novel alternative strategies is a major concern in agriculture to sustain pest management. The marc extract of red grape cultivars reveals plant defence inducer properties. Treatment with grape marc extract efficiently induced hypersensitive reaction-like lesions with cell death evidenced by Evans Blue staining of tobacco leaves. Examination of the infiltration zone and the surrounding areas under UV light revealed the accumulation of autofluorescent compounds. Both leaf infiltration and a foliar spray of the red grape extract on tobacco leaves induced defence gene expression. The PR1 and PR2 target genes were upregulated locally and systemically in tobacco plants following grape marc extract treatment. The grape extract elicited an array of plant defence responses making this natural compound a potential phytosanitary product with a challenging issue and a rather attractive option for sustainable agriculture and environmentally friendly practices

Cloud Microorganisms, an Interesting Source of Biosurfactants

A new scientific hypothesis states that biosurfactants from cloud microorganism origin could change the surface tension of aerosols and thus the mode of precipitations. In order to check this hypothesis, our team has screened a collection of 480 microbial strains isolated from cloud waters for the production of biosurfactants and showed that 42% of these strains were producing such molecules. In the present work, we isolated and identified by LC-MS-MS lipopeptides produced from three strains issued from this screening. Viscosin and massetolide E (cyclic lipopeptides) were produced by Pseudomonas sp. PDD-14b-2, and syringafactins (linear lipopeptides) were produced by Xanthomonas campestris PDD-32b-52 and Pseudomonas syringae PDD-32b-74. The critical micelle concentration (CMC) of these biosurfactants was determined using the pendant drop method. Finally, two approaches of molecular dynamics were used to model the conformation of viscosin and syringafactin A at the water-air interface: one is based on all-atoms simulation (CHARMM force field), while the other one on coarse-grain (CG) simulation (MARTINI force field). To conclude, this work shows how the biodiversity of the cloud microbiota can be explored to search and produce biosurfactants of interest both for atmospheric sciences and also for biotechnological applications

Caractérisation des substances humiques biomimétiques (effets sur les végétaux)

Présentes dans tous les écosystèmes, les substances humiques sont les constituants majeurs de la matière organique. Dans les sols, ces molécules possèdent des effets positifs sur la croissance et le développement des plantes. Cependant, la composition et les propriétés des substances humiques varient selon l'origine et leurs conditions de formation. La transformation physico-chimique d'une matière première végétale homogène permet de préparer des produits de composition stable et reproductible, les substances humiques biomimétiques (SHB), comparables aux substances humiques naturelles. Les objectifs de ce travail visent, d'une part, à déterminer la composition et l'origine des substances humiques biomimétiques à travers leurs caractérisations chimiques; et d'autre part, à évaluer l'efficacité de ces produits sur la croissance et le développement des plantes (pélargonium, maïs) cultivées en culture hors-sol.L'analyse chimique des produits obtenus montre que les substances humiques biomimétiques possèdent les mêmes propriétés que les substances humiques naturelles. Elles sont composées de 60% d'acides humiques dérivés principalement de la lignine et de 40% d'acides fulviques provenant de la cellulose et de l'hémicellulose. L'application de substances humiques biomimétiques induit des effets positifs sur les végétaux pour une dose optimale de 50 mg.L-1 de carbone. La germination et la rhizogenèse du maïs sont stimulées en présence d'extraits humiques. Les effets des substances humiques biomimétiques se traduisent également par la stimulation de la mise à fleur du pélargonium et l'accélération des phases végétatives du maïs. Ces produits semblent agir sur la vitesse des mécanismes de croissance. L'ajout du produit permet aux plants de maïs de réaliser une économie d'eau en réduisant leur consommation. De plus, les acides fulviques semblent plus efficaces que les acides humiques. Ce travail précise l'intérêt des substances humiques biomimétiques et permet d'envisager leur application dans les domaines horticole et agricole.TOULOUSE-ENSAT-Documentation (315552324) / SudocSudocFranceF

Photodegradation of Bentazon, clopyralid, and triclopyr on model leaves: Importance of a systematic evaluation of pesticide photostability on crops

International audiencePhotolyses of three herbicides, bentazon, clopyralid, and triclopyr, were studied on plant leaves after crop treatment. The experiments were carried out on cuticular wax films, which are good models for leaf surfaces. The pure compounds and their commercial formulations were investigated under simulated solar light. At the recommended agricultural application rates, the three formulated herbicides photolyzed more rapidly on films than on soil or in water. Their photolysis is likely to be an important dissipation path from crops after treatment. The effects induced by the adjuvants in formulations were varied. Adjuvants slowed the photodegradation of bentazon slightly. In Garlon, in which triclopyr and clopyralid are combined, the adjuvants did not affect the photolysis of clopyralid even though they accelerated the rate of photolysis of triclopyr by a factor of 7. The kinetics were also affected by the application rates. This work also underscores the importance of assessing the photoreactivity of active ingredients in conditions similar to those of their application

Photoprotection by Plant Extracts: A New Ecological Means To Reduce Pesticide Photodegradation

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High debit sampling of airborne micro and nanoplastics in remote sea

International audienceThe occurrence of micro and nano plastics has been reported in every environmental compartment including marine and freshwaters, soils and sediments, air and atmospheric precipitations.&#160; Recent evidence showing the presence of airborne microplastics in remote ecosystems highlights the extent of this pollution. The atmospheric transportation and the distribution of airborne microplastics still need to be better documented to understand the dynamic of microplastic transfer between ecosystems.While most studies dedicated to the analysis of microplastics in the air use a passive sampling methodology through atmospheric deposition we developed an original stainless device to sample large volumes of air with high debit (2000 L/min) providing a fast sampling of aerosols within a small localized area. An optimized sampling protocol has been deployed in the North Western Mediterranean Sea from the Expedition 7th Continent (E7C) boat. 19 sampling sites have been studied during the E7C expedition in September-October 2019, including measurements in port and coastal areas as well as offshore environments. The analysis of micro/nano plastics was carried out using pyrolysis coupled with gas chromatography and tandem mass spectrometry (Py-GC-MS/MS). This approach allowed us to evaluate the concentrations of micro and nano plastics present in the samples for 5 types of plastics (polypropylene, polystyrene, polymethyl methacrylate, polyethylene terephthalate and polycarbonate) and for 2 size ranges (5-50&#956;m and <5&#956;m).This study confirmed that plastic particles are present in the atmosphere even in remote areas such as the offshore environments. The results showed that airborne micro and nano plastics were detected at each sampling station, from the coast to the open sea, at various concentrations. Py-GC-MS/MS analysis allowed us to quantify the 5 types of polymer and revealed the predominance of PET and PP material. High-volume samplers and &#160;Py-GC-MS/MS analysis have proven to be an efficient and powerful methodology to gather and quantify airborne plastic particles at micro and nanoscale level