Symbiosis of Plants with Mycorrhizal and Endophytic Fungi.

It has long been known that plants and microorganisms coexist [...].

Inoculation with Oidiodendron maius BP Improves Nitrogen Absorption from Fertilizer and Growth of Vaccinium corymbosum during the Early Nursery Stage.

Blueberry roots are inefficient in taking up water and nutrients, a fact partially related to their scarcity of root hairs, but they improve nutrient uptake by associating with ericoid mycorrhizal and endophytic fungi. However, the benefits of this association are both cultivar- and fungus-dependent. Our objective was to assess the effect of inoculation with three native fungal strains (Oidiodendron maius A, O. maius BP, and Acanthomyces lecanii BC) on plantlet growth, plantlet survival, and nitrogen (N) absorption of the southern highbush blueberry (SHB) cultivars Biloxi and Misty. The fungal strains were inoculated into the peat-based substrate for growing blueberry cultivars, and plantlets produced by micropropagation were transplanted and grown for four months. The three inoculated strains positively affected the survival percentage in at least one of the cultivars tested, whereas O. maius BP positively affected plant biomass, N derived from fertilizer absorption, N content, and plant N recovery (%) in both Biloxi and Misty. Our results show that the O. maius BP strain may prove useful as a bio-inoculant to improve blueberry production during the nursery stage.

Can dark septate endophytic fungi (DSE) mobilize selectively inorganic soil phosphorus thereby promoting sorghum growth? A preliminary study / ¿Los hongos endófitos septados oscuros (DSE) pueden movilizar selectivamente el fósforo inorgánico y promover así el crecimiento del sorgo? Un estudio preliminar

Abstract Phosphate fertilizers tend to precipitate with soil components, affecting fertilization efficiency and causing negative environmental effects. Soil microorganisms have been used to solve this problem. However, the ability of dark septate endophytic fungi (DSE) to dissolve phosphates and increase crop yield are not well known. The activity of DSE fungi capable of solubilizing reagent grade phosphates was studied in a Typic Hapludoll (Hapludol típico). The effect of the fungi on the inorganic phosphorus fractions was evaluated and an experiment was conducted in pots with sorghum as a crop. No fungal structures were found in the roots. Curvularia sp. aerial biomass and root length increased; however, P concentration was not affected. Although the results are not conclusive, they represent an advance in the potential use of DSE fungi as P solubilizers to treat crop nutrition.

Resumen Los fertilizantes fosfatados tienden a precipitar con componentes del suelo, lo que afecta la eficiencia de la fertilización y causa efectos negativos. Para resolver este problema se han utilizado microorganismos del suelo. Sin embargo, no se conoce bien la capacidad de los hongos endófitos septados oscuros (ESO) para disolver fosfatos y aumentar el rendimiento de los cultivos. Se estudió en un hapludol típico (typic hapludoll) la actividad de hongos ESO capaces de solubilizar fosfatos de grado reactivo. Se evaluó el efecto de los hongos sobre las fracciones de fósforo inorgánico y se realizó un experimento en macetas con sorgo como cultivo. No se encontraron estructuras fúngicas en las raíces. Curvularia sp. aumentó la biomasa aérea y la longitud radical, pero la concentración de fósforo no se vio afectada. Aunque los resultados no son concluyentes, representan un avance en el uso potencial de hongos ESO como solubilizadores de fósforo para tratar la nutrición de cultivos.

Can dark septate endophytic fungi (DSE) mobilize selectively inorganic soil phosphorus thereby promoting sorghum growth? A preliminary study.

Phosphate fertilizers tend to precipitate with soil components, affecting fertilization efficiency and causing negative environmental effects. Soil microorganisms have been used to solve this problem. However, the ability of dark septate endophytic fungi (DSE) to dissolve phosphates and increase crop yield are not well known. The activity of DSE fungi capable of solubilizing reagent grade phosphates was studied in a Typic Hapludoll (Hapludol típico). The effect of the fungi on the inorganic phosphorus fractions was evaluated and an experiment was conducted in pots with sorghum as a crop. No fungal structures were found in the roots. Curvularia sp. aerial biomass and root length increased; however, P concentration was not affected. Although the results are not conclusive, they represent an advance in the potential use of DSE fungi as P solubilizers to treat crop nutrition.

Dark septate endophytes (DSE): potential bioremedial promoters of oil derivatives.

Oil spills are a global environmental problem. One of the management tools used to solve this problem is phytoremediation, a process that uses the capacity of plants and microorganisms to metabolize the components of the oil. The aims of the present study were to isolate, identify and characterize the fungi obtained from plants growing in an oil-contaminated area and evaluate their growth response and emulsifying and degrading capacity in two petroleum derivatives (kerosene and lube oil). Four dark septate endophytes (DSE) strains were isolated and identified: Exserohilum pedicellatum, Ophiosphaerella sp., and two Alternaria alternata strains. E. pedicellatum was found in an oil-contaminated environment for the first time. All strains were grown in kerosene, although some showed inhibition, whereas in lube oil, all showed growth induction. Ophiosphaerella sp. showed "drops" in kerosene, but the four strains showed surfactant capacity in lube oil. Ophiosphaerella sp. showed the highest emulsifying activity index but both A. alternata strains presented the highest lube oil degradation, which was directly related to the weight of the fungal biomass. There was not relationship between emulsifying capacity and oil degradation. However, these fungi show technological potential for application in phytoremediation processes.

Lead effects on Brassica napus photosynthetic organs.

In this study, effects of lead on ultracellular structure and pigment contents of Brassica napus were examined. Pb(II) was added in soluble form to soil prior to sowing. Pb contents were measured in plant organs at the ontogenetic stages of flowering (FL) and physiological maturity (PM). Pigment contents were evaluated through reflectance measurements. Pb content in organs was found to decrease in the order; roots>stems>leaves. Lead content in senescent leaves at FL stage was significantly higher than harvested leaves, strongly suggesting a detoxification mechanism. Leaves and stems harvested at the PM stage showed damage at subcellular level, namely chloroplast disorganization, cell wall damage and presence of osmiophilic bodies. Chlorophyll content increased in the presence of Pb at the FL stage, compared with control; at the PM stage, chlorophyll contents decreased with low Pb concentration but showed no significant differences with control at high Pb soil concentration. The results suggest an increase in antioxidants at low Pb concentration and cell damage at higher lead concentration.

Protective effect exerted by soil phosphorus on soybean subjected to arsenic and fluoride.

Objetive: Arsenic (As) and fluoride (F) are found in groundwater and soils around the world, causing different problems to crops. Because these elements compete against phosphorus (P) in soils and plants, their relationship is complex. The aim of this work was to study the oxidative stress of soybean plants subjected to different concentrations of As and F, and the effect of P. METHODS: The following 10 treatments were carried out in each of two soils with different P content: three As levels (low 10 mg As kg-1, medium 50 mg As kg-1 and high 100 mg As kg-1), three F levels (low 160 mg F kg-1, medium 250 mg F kg-1 and high 500 mg F kg-1) and three As + F levels (same concentrations), and the control treatment (soil with the background As and F concentrations) Lipid peroxidation, chlorophyll, gluthatione contents and antioxidant enzymes activities were determination. RESULTS: Increased lipid peroxidation and alterations in glutathione content, catalase, superoxide dismutase and peroxidase activities as well as in chlorophyll content revealed that As causes higher oxidative stress in plants grown in soils with low P content. CONCLUSION: Stress parameters in F treatments were less affected. Plants grown in soils enriched with P revealed a decrease in the toxic effects caused by As and F.

Arbuscular mycorrhiza detoxifying response against arsenic and pathogenic fungus in soybean.

Uptake of Arsenic (As) in plant tissues can affect metabolism, causing physiological disorders, even death. As toxicity, but also pathogen infections trigger a generalised stress response called oxidative stress; however knowledge on the response of soybean (Glycine max L.) under multiple stressors is limited so far. Arbuscular mycorrhizal fungi (AMF) enhance the tolerance of host plants to abiotic and biotic stress. Thus, we investigated the effects of the AMF Rhizophagus intraradices on soybean grown in As-contaminated soils as well as in the presence of the pathogen Macrophomina phaseolina (charcoal rot of the stem). Plant parameters and degree of mycorrhizal colonization under the different assessed treatments were analyzed. Content of As in roots and leaves was quantified. Increasing As level in the soil stopped plant growth, but promoted plant As uptake. Inoculation of soybean plants with M. phaseolina accentuated As effect at all physiological levels. In the presence of mycorrhizal symbiosis biomass dramatically increased, and significantly reduced the As concentration in plant tissues. Mycorrhization decreased oxidative damage in the presence of both As and the pathogen. Furthermore, transcription analysis revealed that the high-affinity phosphate transporter from R. intraradices RiPT and the gene encoding a putative arsenic efflux pump RiArsA were up-regulated under higher As doses. These results suggest that R. intraradices is most likely to get involved in the defense response against M. phaseolina, but also in the reduction of arsenate to arsenite as a possible detoxification mechanism in AMF associations in soybean. CAPSULE ABSTRACT: R. intraradices actively participates in the soybean antioxidant defense response against arsenic stress and M. phaseolina infection.

Effects of phytoremediation and application of organic amendment on the mobility of heavy metals in a polluted soil profile.

This research aims to assess the effect of the application of biosolids compost and phytoremediation on the mobility of total and biodisponibles (DTPA) fractions of cadmium, copper, lead, and zinc from different horizons of a superficially contaminated soil. Leaching experiment in soil columns was proposed. Treatments contemplated application of compost biosolid and phytoremediation. Two destructive samplings were performed. Total and DTPA trace metals were identified in each horizon. The overall performance of the various elements in its total and DTPA forms show greater concentration in horizon A and fewer gradients between horizons Bt and BC, thus assuming that the high content of clay in horizon Bt (62.9%) limits its movement through the horizons. In the mobile nutrients, a greater mobility was evidenced in DTPA fractions if compared to Total fractions. In the horizon A, the more mobile metals, such as Zn and Cd, evidenced a greater percentage of DTPA/Total fractions in all treatments. The application of compost with or without plant diminished the mobilization of Zn, Cu, and Cd Total, thus limiting a potential leaching to inferior horizons. However, this effect was not observed in the DTPA fraction.

Concentration of potentially toxic elements in field crops grown near and far from cities of the Pampas (Argentina).

Soils of the Pampas show no signs of contamination with potentially toxic elements (PTEs), except in the areas that surround cities. The concentration of PTE in crops grown in this region is in most cases unknown. Our objective was to determine the PTE concentration in main field crops and pastures grown in 'a priori' non-contaminated areas and in potentially contaminated areas around cities. Forty-eight plots from farms located far from cities or roads and 36 plots from farms located very close to cities or to high traffic roads were sampled. The area ranged from 33 degrees 40' S to 36 degrees 0' S and from 57 degrees 35' W to 61 degrees 22' W. Maize, soybean, wheat, grazed grassland and pastures, and their top soils were sampled. All samples were acid digested. Cadmium, zinc, chromium, copper, nickel and lead were determined using ICPES. Standard t-tests were performed. All soils were within the known normal values of soil PTE concentrations, with the exception of a few cases around cities. PTE accumulation on grains and aerial biomass is considered almost negligible in crops grown in both studied areas, with the exception of a few elements in soybean. PTE concentrations in crops and pastures are in keeping with the low content of trace metals found in soils of the Pampas.

¿El tratamiento de digestión de biosólidos reduce el riesgo de acumulación de elementos potencialmente tóxicos en maíz?

El tratamiento secundario de los biosolidos se aplica para reducir la presencia de patógenos, por lo que se hipotetizó que ese tratamiento reduciría también la concentración de elementos potencialmente tóxicos, reduciendo su poder contaminante. En experimentos de campo se determinaron los niveles de cadmio, cinc, cromo, cobre, níquel, y plomo en suelo, planta y grano de maízes abonados con biosólidos que recibieron tratamiento primario y secundario

Acquisition and allocation of resources in two waterlogging-tolerant grasses.

This study focuses on the following questions: (i) whether reductions in root:shoot ratio have a cost in terms of nutrient balance of the plant, and (ii) whether changes in resource-allocation patterns are proportional among different resources. Our approach was to analyse the variations in the allocation pattern induced by soil waterlogging. A pot experiment was conducted to analyse the effects of waterlogging on biomass, phosphorus (P) and nitrogen (N) accumulation of Paspalum dilatatum and Danthonia montevidensis, two waterlogging-tolerant grasses. When changing from oxic to anoxic conditions, a common response of these and other waterlogging-tolerant grasses is a reduction in allocation to below-ground resources. It was observed that (i) the reduction in root:shoot ratio caused by waterlogging did not have a cost in terms of capacity for nutrient uptake; (ii) resource partitioning within aerial parts was less sensitive to treatments than partitioning between roots and shoots; and (iii) biomass does not appear to be a useful currency for evaluating nutrient-allocation patterns, as the allocation of P and N was inadequately represented by biomass. The results presented here indicate that the existence of compensation mechanisms reduces the predictive value of the partition of resources for the capacity of plants to acquire resources. Data on the allocation of nutrients in relation to biomass suggest that the assumptions of independence in the allocation pattern between biomass and limiting nutrients under the effects of environmental factors can be extended.

Ensayos a gran escala de valoracion directa de biosolidos

En la Argentina va creciendo la conciencia ecologica y en ese escenario se inserta el proyecto de valoracion agricola de los biosolidos en plantas depuradoras de la ciudad de Buenos Aires. La valoracion agricola constituye una solucion logica que permitira aportar nutrientes a los cultivos y dar uso racional a los desechos cloacales, ya que los biosolidos son un importante proveedor de carbono y nutrientes a los suelos. Se describen experiencias realizadas en areas que cubren un arco de hasta 200 kilometros alrededor de la ciudad de Buenos Aires

Mechanisms for the increase in phosphorus uptake of waterlogged plants: soil phosphorus availability, root morphology and uptake kinetics.

Waterlogging frequently reduces plant biomass allocation to roots. This response may result in a variety of alterations in mineral nutrition, which range from a proportional lowering of whole-plant nutrient concentration as a result of unchanged uptake per unit of root biomass, to a maintenance of nutrient concentration by means of an increase in uptake per unit of root biomass. The first objective of this paper was to test these two alternative hypothetical responses. In a pot experiment, we evaluated how plant P concentration of Paspalum dilatatum, (a waterlogging-tolerant grass from the Flooding Pampa, Argentina) was affected by waterlogging and P supply and how this related to changes in root-shoot ratio. Under both soil P levels waterlogging reduced root-shoot ratios, but did not reduce P concentration. Thus, uptake of P per unit of root biomass increased under waterlogging. Our second objective was to test three non-exclusive hypotheses about potential mechanisms for this increase in P uptake. We hypothesized that the greater P uptake per unit of root biomass was a consequence of: (1) an increase in soil P availability induced by waterlogging; (2) a change in root morphology, and/or (3) an increase in the intrinsic uptake capacity of each unit of root biomass. To test these hypotheses we evaluated (1) changes in P availability induced by waterlogging; (2) specific root length of waterlogged and control plants, and (3) P uptake kinetics in excised roots from waterlogged and control plants. The results supported the three hypotheses. Soil P avail-ability was higher during waterlogging periods, roots of waterlogged plants showed a morphology more favorable to nutrient uptake (finer roots) and these roots showed a higher physiological capacity to absorb P. The results suggest that both soil and plant mechanisms contributed to compensate, in terms of P nutrition, for the reduction in allocation to root growth. The rapid transformation of the P uptake system is likely an advantage for plants inhabiting frequently flooded environments with low P fertility, like the Flooding Pampa. This advantage would be one of the reasons for the increased relative abundance of P. dilatatum in the community after waterlogging periods.