Ricardo Luis Louro Berbara

Diversity and functionality of arbuscular mycorrhizal fungi in three plant communities in semiarid Grasslands National Park, Canada.

Septate endophytes proliferating in the roots of grasslands’ plants shed doubts on the importance of arbuscular mycorrhizal (AM) symbioses in dry soils. The functionality and diversity of the AM symbioses formed in four replicates of three adjacent plant communities (agricultural, native, and restored) in Grasslands National Park, Canada were assessed in periods of moisture sufficiency and deficiency typical of early and late summer in the region. The community structure of AM fungi, as determined by polymerase chain reaction-denaturing gradient gel electrophoresis, varied with sampling time and plant community. Soil properties other than soil moisture did not change significantly with sampling time. The DNA sequences dominating AM extraradical networks in dry soil apparently belonged to rare taxa unreported in GenBank. DNA sequences of Glomus viscosum, Glomus mosseae, and Glomus hoi were dominant under conditions of moisture sufficiency. In total, nine different AM fungal sequences were found suggesting a role for the AM symbioses in semiarid areas. Significant positive linear relationships between plant P and N concentrations and active extraradical AM fungal biomass, estimated by the abundance of the phospholipid fatty acid marker 16:1ω5, existed under conditions of moisture sufficiency, but not under dry conditions. Active extraradical AM fungal biomass had significantly positive linear relationship with the abundance of two early season grasses, Agropyron cristatum (L.) Gaertn. and Koeleria gracilis Pers., but no relationship was found under dry conditions. The AM symbioses formed under conditions of moisture sufficiency typical of early summer at this location appear to be important for the nutrition of grassland plant communities, but no evidence of mutualism was found under the dry conditions of late summer.

Ocorrência de fungos micorrízicos arbusculares em áreas revegetadas após mineração de bauxita em Porto Trombetas, Pará

The objective of this study was to evaluate the structure and diversity of arbuscular mycorrhizal fungi (AMF) in revegetated areas at Porto Trombetas, Para, Brazil. Composite samples were collected in August (dry season) and April (wet season) in areas with top soil after 2, 4, 6, 12 and 16 years of revegetation, in area without the top soil or vegetation, and in a pristine forest. The AMF spores were extracted, and the species identified. The relative density and frequency of occurrence of each species, the Shannon-Wiener and Simpson indexes were calculated. The results indicated that the density of AMF spores did not differ significantly with season. However, the number of AMF species was significantly higher in the dry season at the pristine forest and in the area two years after revegetation. Among the AMF species, Glomus macrocarpum and Acaulospora mellea were represented in higher numbers. After two years of planting, the diversity was highest and the dominance of AMF species was lowest. The addition of top soil with the planting of mycorrhizal seedlings were efficient to colonize areas with AMF after open cast bauxite mining.

Correlation of Total Phenolic and Flavonoid Contents of Brazilian Honeys with Colour and Antioxidant Capacity

Sixty Brazilian honey samples were analysed for their total phenolic content with the Folin-Denis reagent, total flavonoid content by aluminium chloride method, and antioxidant activity by reaction with 2,2-diphenyl-1-picrylhydrazyl radical. Colour was also classified according to visual analysis and Pfund scale. Linear relationships were observed between colour and flavonoid content, total phenolics and antioxidant capacity, and total flavonoid and phenolic contents. The white-coloured Citrus honey showed the lowest antioxidant activity, while the light ambar Verbenaceae honey showed the highest total phenolics and antioxidant activity. Dark-coloured and polyfloral honeys, though less popularized among consumers, showed average to high antioxidant capacity.

Structure-Property-Function Relationship in Humic Substances to Explain the Biological Activity in Plants.

Knowledge of the structure-property-function relationship of humic substances (HSs) is key for understanding their role in soil. Despite progress, studies on this topic are still under discussion. We analyzed 37 humic fractions with respect to their isotopic composition, structural characteristics, and properties responsible for stimulating plant root parameters. We showed that regardless of the source of origin of the carbon (C3 or C4), soil-extracted HSs and humic acids (HAs) are structurally similar to each other. The more labile and functionalized HS fraction is responsible for root emission, whereas the more recalcitrant and less functionalized HA fraction is related to root growth. Labile structures promote root stimulation at lower concentrations, while recalcitrant structures require higher concentrations to promote a similar stimulus. These findings show that lability and recalcitrance, which are derived properties of humic fractions, are related to the type and intensity of their bioactivity. In summary, the comparison of humic fractions allowed a better understanding of the relationship between the source of origin of plant carbon and the structure, properties, and type and intensity of the bioactivity of HSs in plants. In this study, scientific concepts are unified and the basis for the agronomic use of HSs is established.

Fungos micorrízicos arbusculares em estéril revegetado com Acacia mangium, após mineração de bauxita

RESUMO – O objetivo deste trabalho foi avaliar a composicao das comunidades de FMAs em areas revegetadas com Acacia mangium apos a mineracao de bauxita na regiao de Porto Trombetas, PA. Foram coletadas amostras de solo compostas nos periodos seco e chuvoso, em areas revegetadas com Acacia mangium, que receberam inoculos de Glomus clarum e Gigaspora margarita, com 1 e 5 anos de idade. Os solos foram revegetados sem a reposicao do horizonte superficial orgânico. Os esporos dos fungos micorrizicos arbusculares (FMAs) foram extraidos e identificados atraves de suas caracteristicas morfologicas. Analisou-se a densidade de esporos e de especies em cada amostra, a densidade relativa e a frequencia de ocorrencia de cada especie por periodo de amostragem, alem do indice de abundância e frequencia (IAF). Sob o plantio de mudas de A. mangium, a densidade de esporos de FMAs foi elevada e aumentou com a idade, enquanto o numero de especies nao variou. Glomus clarum produz alta densidade de esporos na fase inicial do plantio e declina com o tempo, e Gigaspora margarita nao esporula nas condicoes edafoclimaticas locais. A maioria das especies de FMA nao apresenta o mesmo padrao de esporulacao nos periodos seco e chuvoso. Palavras-chave: Taxonomia, micorrizas, sazonalidade e areas degradadas.

Much beyond Mantel: Bringing Procrustes Association Metric to the Plant and Soil Ecologist’s Toolbox

The correlation of multivariate data is a common task in investigations of soil biology and in ecology in general. Procrustes analysis and the Mantel test are two approaches that often meet this objective and are considered analogous in many situations especially when used as a statistical test to assess the statistical significance between multivariate data tables. Here we call the attention of ecologists to the advantages of a less familiar application of the Procrustean framework, namely the Procrustean association metric (a vector of Procrustean residuals). These residuals represent differences in fit between multivariate data tables regarding homologous observations (e.g., sampling sites) that can be used to estimate local levels of association (e.g., some groups of sites are more similar in their association between biotic and environmental features than other groups of sites). Given that in the Mantel framework, multivariate information is translated into a pairwise distance matrix, we lose the ability to contrast homologous data points across dimensions and data matrices after their fit. In this paper, we attempt to familiarize ecologists with the benefits of using these Procrustean residual differences to further gain insights about the processes underlying the association among multivariate data tables using real and hypothetical examples.

Lunularia cruciata, a potential in vitro host for Glomus proliferum and G. intraradices

A study was conducted to define culture conditions for in vitro growth arbuscular mycorrhizal fungi (AMF) with liverworts as hosts. Lunularia cruciata (L.) Dumortier ex. Lindberg developed in vitro monoxenic mycothalli with both Glomus proliferum Dalpé & Declerck (MUCL 41827) and Glomus intraradices Schenck & Smith (MUCL 43204). AMF inoculated plants were co-cultured in plastic Petri dishes with semi-solidified medium supplemented with sucrose and grown under filtered light. Mycothalli of L. cruciata produced external hyphae and spores in quantities equivalent to those obtained with Ri T-DNA transformed root systems.

Humic Substances and Plant Defense Metabolism

Humic substances (HS) affect most plant metabolic processes. Regardless of their source, HS help regulate enzymatic systems related to primary, secondary, and defense metabolisms in response to environmental stress. Morphologically, the HS–plant interaction results in increased root length and the emanation of lateral roots. These morphological changes occur in response to complex regulatory and stress response processes activated by the application of HS and similar chemical fractions. Given that the roots are the main plant organs that interact with HS, HS–root interaction mechanisms are one of the most important topics in HS–plant research. Specifically, there is a known biochemical relationship between humic compounds and major plant metabolic processes. New findings about the modes of metabolite action in plants have increased our understanding of how HS help to optimize plant metabolism. Advanced technologies, such as large-scale and spectroscopy, have also increased our understanding of the modes of action of HS. The application of techniques such as amplified fragment length polymorphism (AFLP) and microarray analysis in study of HS-treated plants has demonstrated that approximately 6.1–9 % of differentially expressed genes correspond to metabolic pathways that are associated with defense mechanisms in response to stimuli. These results suggest that HS induce plant adaptive responses to environmental stress. In this study, we discuss how HS contribute to improved plant performance through complex metabolic mechanisms. We apply new findings about the modes of action of metabolites related to antioxidant mechanisms to understand HS modes of action and examine HS effects in plants by using spectroscopic techniques to study root interactions. We also propose a framework for investigating the use of HS in agriculture to improve the growth of food plants grown in high-stress environments.

Respostas de Acacia mangium Willd e Sclerolobium paniculatum Vogel a fungos micorrízicos arbusculares nativos provenientes de áreas degradadas pela mineração de bauxita na Amazônia

The responses of Acacia mangium Willd (mangium) and Sclerolobium paniculatum Vogel (tachi) to arbuscular mycorrhizal fungi (AMF) inoculation collected from areas under reclamation after bauxite mining, was evaluated in an completely randomized design distributed in 14 treatments (two legume, species and seven soil types), with three replicates. Evaluated were the number of spores in the soil, the mycorrhizal colonization, the total dry matter, accumulated P, the mycorrhizal dependence of the seedlings and the abundance and the frequency of species. The number of infective propagules (NIP) was studied in a randomized block design, with eight dilutions of soil inoculum, five replicates and a trap plant (Brachiaria decumbens Stapf). Substratum of a Planosol, mixed with washed sand (1:1 v:v), and phosphate of rock Araxa (0.60 g/kg) was used. The number of spores increased in function of time covering of legumes. The mycorrhizal colonization was more intense in tachi. The values of dry matter of that species were inferior to the mangium, that extracted six times larger P of substratum. In general, mangium, contrary to tachi, was facultative to presence of AMF, suggesting the use in degraded areas without previous inoculation. Among the 39 species of identified AMF, Glomus macrocarpum Tul. & Tul. showed higher index of abundance and frequency (IAF) and higher NIP, standing among pioneering species, while others appeared only under more developed forest of the areas in reclamation.

Relationship between Physical and Chemical Soil Attributes and Plant Species Diversity in Tropical Mountain Ecosystems from Brazil

Although the high diversity of plant species in the rupestrian fields has been primarily attributed to the existence of a set of distinct habitats, few studies support this assertion. The present study aimed to further investigate the relationship between physical and chemical attributes of soils with the diversity of plant species in this unique ecosystem. The rupestrian field is a unique vegetation formation that covers some of the southeastern Brazilian mountains in the transition of the Atlantic rain forest and the Cerrado (savanna). Different habitats occur according to soil characteristics (e.g., presence of rocks, sand, fertility, hydrology, etc.). These attributes ultimately influence the vegetation that is highly adapted to the harsh edaphic and climatic mountain conditions. Five distinct habitats were studied by us: rocky outcrops, peat bogs, sandy bogs, quartz gravel fields, and “cerrado” (savanna). A floristic survey indicated that four families are found at greater frequency: Poaceae, Asteraceae, Cyperaceae, and Leguminosae. The greatest diversity of plant species was found in the rocky outcrops habitat, followed by cerrado, peat bog, quartz gravel grassland, and sandy bogs, respectively. The main difference in the floristic composition among these habitats was related to the dominant species. Trachypogon spicatus (Poaceae) was the most dominant species in the rocky outcrops, Axonopus siccus (Poaceae) in the peat bogs, Lagenocarpus rigidus (Cyperaceae) in the sandy bogs, Schizachyrium tenerum (Poaceae) in the cerrado, while Vellozia sp. 8 (Velloziaceae) dominated the vegetation in the quartz gravel grassland. This study demonstrated that physical and chemical soil properties strongly related the diversity of plant species occurring in the different habitats of rupestrian fields.