Jerusa Schneider

Arbuscular mycorrhizal fungi in arsenic-contaminated areas in Brazil

Arbuscular mycorrhizal fungi (AMF) are ubiquitous and establish important symbiotic relationships with the majority of the plants, even in soils contaminated with arsenic (As). In order to better understand the ecological relationships of these fungi with excess As in soils and their effects on plants in tropical conditions, occurrence and diversity of AMF were evaluated in areas affected by gold mining activity in Minas Gerais State, Brazil. Soils of four areas with different As concentrations (mg dm(-3)) were sampled: reference Area (10); B1 (subsuperficial layer) (396); barren material (573), and mine waste (1046). Soil sampling was carried out in rainy and dry seasons, including six composite samples per area (n = 24). AMF occurred widespread in all areas, being influenced by As concentrations and sampling periods. A total of 23 species were identified, belonging to the following genus: Acaulospora (10 species), Scutellospora (4 species), Racocetra (3 species), Glomus (4 species), Gigaspora (1 species) and Paraglomus (1 species). The most frequent species occurring in all areas were Paraglomus occultum, Acaulospora morrowiae and Glomus clarum. The predominance of these species indicates their high tolerance to excess As. Although arsenic contamination reduced AMF species richness, presence of host plants tended to counterbalance this reduction.

Phytoprotective Effect of Arbuscular Mycorrhizal Fungi Species Against Arsenic Toxicity in Tropical Leguminous Species

Arbuscular mycorrhizal fungi (AMF) improve the tolerance of hosting plants to arsenic (As) in contaminated soils. This work assessed the phytoprotective effect of Glomus etunicatum, Acaulospora morrowiae, Gigaspora gigantea, and Acaulospora sp. on four leguminous species (Acacia mangium, Crotalaria juncea, Enterolobium contortisiliquum, and Stizolobium aterrimum) in an As-contaminated soil from a gold mining area. AMF root colonization, biomass production, As and P accumulation, as well as arsenic translocation index (TI) from roots to shoots were measured. The AMF phytoprotective effect was assessed by the P/As ratio and the activity of plant antioxidant enzymes. The AMF colonization ranged from 24 to 28%. In general, all leguminous species had low As TI when inoculated with AMF species. Inoculation of C. juncea with Acaulospora sp. improved significantly As accumulation in roots, and decreased the activity of ascorbate peroxidase (APX) and superoxide dismutase (SOD), highlighting its phytoprotective effect and the potential use of this symbiosis for phytoremediation of As-contaminated soils. However, S. aterrimum has also shown a potential for phytoremediation irrespectively of AMF inoculation. APX was a good indicator of the phytoprotective effect against As contamination in C. juncea and A. mangium. In general P/As ratio in shoots was the best indicator of the phytoprotective effect of all AMF species in all plant species.

Anatomy and ultrastructure alterations of Leucaena leucocephala (Lam.) inoculated with mycorrhizal fungi in response to arsenic-contaminated soil

Many studies demonstrate the potential application of arbuscular mycorrhizal fungi (AMF) for remediation purposes, but little is known on AMF potential to enhance plant tolerance to arsenic (As) and the mechanisms involved in this process. We carried anatomical and ultrastructural studies to examine this symbiotic association and the characteristics of shoots and roots of Leucaena leucocephala in As-amended soils (35 and 75 mg As dm(-3)). The experiment used 3 AMF isolates from uncontaminated soils: Acaulospora morrowiae, Glomus clarum, and Gigaspora albida; a mixed inoculum derived from combining these 3 isolates (named Mix AMF); and, 3 AMF isolates from As-contaminated areas: A. morrowiae, G. clarum and Paraglomus occultum. Phytotoxicity symptoms due to arsenic contamination appeared during plant growth, especially in treatments without AMF application. Inoculation with G. clarum and the mixture of species (A. morrowiae, G. albida, and G. clarum) resulted in better growth of L. leucocephala in soils with high As concentrations, as well as significant As removal from the soil, showing a potential for using AMF in phytoextraction. Light microscopy (LS), transmission (TEM) and scanning electron microscopies (SEM) studies showed the colonization of the AMF in plant tissues and damage in all treatments, with ultrastructural changes being observed in leaves and roots of L. leucocephala, especially with the addition of 75 mg dm(-3) of As.

Espécies tropicais de pteridófitas em associação com fungos micorrízicos arbusculares em solo contaminado com arsênio

The symbiosis of plants with mycorrhizal fungi represents an alternative to be considered during the processes of revegetation and rehabilitation of arsenic-contaminated soil. The aim of this study was to evaluate under greenhouse conditions the effect of arsenic on the mycorrhizal association of two species of tropical fern (Thelypteris salzmannii and Dicranopteris flexuosa). T. salzmannii had higher rates of colonization and higher density of spores while D. flexuosa showed greater sensitivity to smaller concentrations of arsenic and association with mycorrhizal fungi. Our results indicate that screening and selection of mycorrhizal fungal isolates/species is possible and effective for phytoremediation of arsenic-contaminated soils.

Arbuscular mycorrhizal fungi-assisted phytoremediation of a lead-contaminated site

Knowledge of the behavior of plant species associated with arbuscular mycorrhizal fungi (AMF) and the ability of such plants to grow on metal-contaminated soils is important to phytoremediation. Here, we evaluate the occurrence and diversity of AMF and plant species as well as their interactions in soil contaminated with lead (Pb) from the recycling of automotive batteries. The experimental area was divided into three locations: a non-contaminated native area, a coarse rejects deposition area, and an area receiving particulate material from the chimneys during the Pb melting process. Thirty-nine AMF species from six families and 10 genera were identified. The Acaulospora and Glomus genera exhibited the highest occurrences both in the bulk (10 and 6) and in the rhizosphere soils (9 and 6). All of the herbaceous species presented mycorrhizal colonization. The highest Pb concentrations (mgkg-1) in roots and shoots, respectively, were observed in Vetiveria zizanoides (15,433 and 934), Pteris vitata (9343 and 865), Pteridim aquilinun (1433 and 733), and Ricinus communis (1106 and 625). The diversity of AMF seems to be related to the area heterogeneity; the structure communities of AMF are correlated with the soil Pb concentration. We found that plant diversity was significantly correlated with AMF diversity (r=0.645; P>0.05) in areas with high Pb soil concentrations. A better understanding of AMF communities in the presence of Pb stress may shed light on the interactions between fungi and metals taking place in contaminated sites. Such knowledge can aid in developing soil phytoremediation techniques such as phytostabilization.

Influência de diferentes sistemas de manejo e calagem em experimento de longa duração sobre fungos micorrízicos arbusculares

Visando estudar a influencia de diferentes sistemas de manejo do solo com e sem calagem, sobre a colonizacao micorrizica radicular e a producao de micelio extrarradicular, por meio de tecnica de analise multivariada, utilizou-se um experimento implantado em 1978, no municipio de Guarapuava, PR. A analise de componentes principais comprovou a existencia de efeitos negativos do sistema de preparo convencional do solo sobre a colonizacao de fungos micorrizicos arbusculares (FMAs) do solo, principalmente em estruturas como arbusculos e vesiculas. A calagem apresentou beneficios para os parâmetros de colonizacao micorrizica e comprimento de micelio extrarradicular, sendo mais significativo nos sistemas de manejo conservacionistas, principalmente o sistema de plantio direto. Nas areas de sistemas convencionais ocorreu uma reducao na colonizacao micorrizica e, consequentemente, diminuicao dos efeitos beneficos dos FMAs para as plantas, reduzindo a qualidade do solo e a sustentabilidade.

Publisher Correction: Geochemical constraints on the Hadean environment from mineral fingerprints of prokaryotes

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Geochemical constraints on the Hadean environment from mineral fingerprints of prokaryotes

The environmental conditions on the Earth before 4 billion years ago are highly uncertain, largely because of the lack of a substantial rock record from this period. During this time interval, known as the Hadean, the young planet transformed from an uninhabited world to the one capable of supporting, and inhabited by the first living cells. These cells formed in a fluid environment they could not at first control, with homeostatic mechanisms developing only later. It is therefore possible that present-day organisms retain some record of the primordial fluid in which the first cells formed. Here we present new data on the elemental compositions and mineral fingerprints of both Bacteria and Archaea, using these data to constrain the environment in which life formed. The cradle solution that produced this elemental signature was saturated in barite, sphene, chalcedony, apatite, and clay minerals. The presence of these minerals, as well as other chemical features, suggests that the cradle environment of life may have been a weathering fluid interacting with dry-land silicate rocks. The specific mineral assemblage provides evidence for a moderate Hadean climate with dry and wet seasons and a lower atmospheric abundance of CO2 than is present today.

UTILIZAÇÃO DA ESTRUVITA FORMADA NA PRECIPITAÇÃO QUÍMICA DA AMÔNIA COMO FONTE DE NUTRIENTES PARA PLANTAS

Resumo O projeto teve como objetivo avaliar o potencial da estruvita na liberação de nutrientes essenciais para o desenvolvimento de plantas. Para isso, foi instalado um experimento em casa de vegetação localizada na Faculdade de Engenharia Agrícola. A cultura utilizada foi a alface lisa, cultivar Regiane. Após colhidas, a parte aérea foi separada da radicular, pesadas e colocadas cada parte em sacos para serem levadas à estufa, a análise de massa fresca da parte aérea (MFPA) e número de folhas (NF) maiores ou iguais a 6 cm. Concluiu-se que o tratamento que recebeu apenas estruvita com o dobro da dose recomendada de P apresentou, em média, o maior número de folhas e uma maior produção de fitomassa com tendência de aumento de produção conforme a dosagem de estruvita era aumentada. Além disso, o tratamento que recebeu estruvita+carnalita com o dobro da dose recomendada de P apresentou resultados próximos ao do adubo comercial NPK 10:10:10.

Potential Promising Set of Plant–Microbe Interactions for the Revegetation of Open-Pit Mining and Smelting Areas in Brazil

Mineral exploitation is an essential modern society activity, providing resources for industry and agriculture. However, mining has disturbing effects on the local environment. Environments under influence of mining are often devoid of natural means of biotic regeneration, requiring human intervention for the revegetation. Phytoremediation has proven to be a very promising technique for in situ rehabilitation of these environments. Plant–microbe interactions, especially arbuscular mycorrhizal and legume-rhizobia symbioses have real potential for phytoremediation approaches in the revegetation of mining and smelting contaminated soils. In Brazil, studies are ongoing on the role of both mycorrhizal and legume-rhizobia symbioses as plant growth promoters in contaminated soils. Promising results have provided valuable information to assist the next step that is to apply this biotechnology in field conditions. Although promising results already have been achieved from controlled conditions, more work is needed for a deep understanding of the mechanisms, as the expression/suppression of genes, in both plant and microorganisms, linked to the symbiosis and phytoprotection under trace elements contamination.