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

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

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

Toxicity of Neurons Treated with Herbicides and Neuroprotection by Mitochondria-Targeted Antioxidant SS31

The purpose of this study was to determine the neurotoxicity of two commonly used herbicides: picloram and triclopyr and the neuroprotective effects of the mitochondria-targeted antioxidant, SS31. Using mouse neuroblastoma (N2a) cells and primary neurons from C57BL/6 mice, we investigated the toxicity of these herbicides, and protective effects of SS1 peptide against picloram and triclopyr toxicity. We measured total RNA content, cell viability and mRNA expression of peroxiredoxins, neuroprotective genes, mitochondrial-encoded electron transport chain (ETC) genes in N2a cells treated with herbicides and SS31. Using primary neurons from C57BL/6 mice, neuronal survival was studied in neurons treated with herbicides, in neurons pretreated with SS31 plus treated with herbicides, neurons treated with SS31 alone, and untreated neurons. Significantly decreased total RNA content, and cell viability in N2a cells treated with picloram and triclopyr were found compared to untreated N2a cells. Decreased mRNA expression of neuroprotective genes, and ETC genes in cells treated with herbicides was found compared to untreated cells. Decreased mRNA expression of peroxiredoxins 1–6 in N2a cells treated with picloram was found, suggesting that picloram affects the antioxidant enzymes in N2a cells. Immunofluorescence analysis of primary neurons revealed that decreased neuronal branching and degenerating neurons in neurons treated with picloram and triclopyr. However, neurons pretreated with SS31 prevented degenerative process caused by herbicides. Based on these results, we propose that herbicides—picloram and triclopyr appear to damage neurons, and the SS31 peptide appears to protect neurons from herbicide toxicity