Neighboring Plants Research Articles

The influence of the vitiated air from the treatment plants on the urban and rural development

In order to reduce the emissions produced by the operational flow of a wastewater treatment plant, regardless of whether they are located in urban or rural areas, the quality of air must be analyzed. For this reason, the Constanta Nord treatment plant was chosen as a study location. This is near the Mamaia resort and does not fall within the recommended sanitary protection norms, according to NP-032-1999 (at least 300 m from the last house). Therefore, it was necessary to take measures to reduce the repellent gases generated in the neighborhood of wastewater treatment plants. The solution is in attention of all wastewater treatment plants from the world because this depend on operational flux management and health of population.The research consists of: description of the technological flow of the treatment plant and in particular of the deodorizing installation of the contaminated air, choosing a work scenario for a day with 2 shifts per hour, respectively 6 shifts per hour, the air flow needed to treat the vitiated air (the deodorization plant components) and the efficiency of the regulation system from the point of view of energy consumption. Also, possible leakage of dangerous gases into the atmospheric air was monitored (H2S, Cl2, CO), taking into account the fact that in the immediate vicinity there is the Mamaia resort, the student housing and rural locations Palazu and Mamaia village.

Red Palm Weevil Detection Methods: A Survey

Many pests affect plants, and these have a negatively affected agricultural production and cause a lack of quality. These causes an economic loses and high poverty rates. Many types of pests infest trees like insects, viruses, bacteria, and harmful parasitic plants. One of the most dangerous insects that infest trees such as [date, canary, sago, oil, coconut, etc…] is the Red Palm Weevil (RPW). RPW is currently considered as a global pest, killing trees, increases the tree temperature and causes water stress. It lays the eggs inside the trunk of the tree and starts feeding on the tissue of the plant, then begins to move inside the tree and still inside it until the tree dies, then begin move to the neighboring plants. The early detection of this destructive weevil is not easy; because the visible infection symptoms appear only when the infection stage is dangerous. There are many detection methods for discovering the infected trees, a Visual Inspection, Acoustic Detection, Chemical Detection, and Thermal remote sensing. In this research, we will discuss the different methods used for the early detection of this harmful weevil.

Pathogenic Bacteria Target Plant Plasmodesmata to Colonize and Invade Surrounding Tissues.

A hallmark of multicellular organisms is their ability to maintain physiological homeostasis by communicating among cells, tissues, and organs. In plants, intercellular communication is largely dependent on plasmodesmata (PD), which are membrane-lined channels connecting adjacent plant cells. Upon immune stimulation, plants close PD as part of their immune responses. Here, we show that the bacterial pathogen Pseudomonas syringae deploys an effector protein, HopO1-1, that modulates PD function. HopO1-1 is required for P. syringae to spread locally to neighboring tissues during infection. Expression of HopO1-1 in Arabidopsis (Arabidopsis thaliana) increases the distance of PD-dependent molecular flux between neighboring plant cells. Being a putative ribosyltransferase, the catalytic activity of HopO1-1 is required for regulation of PD. HopO1-1 physically interacts with and destabilizes the plant PD-located protein PDLP7 and possibly PDLP5. Both PDLPs are involved in bacterial immunity. Our findings reveal that a pathogenic bacterium utilizes an effector to manipulate PD-mediated host intercellular communication for maximizing the spread of bacterial infection.

Plasticity of barley in response to plant neighbors in cultivar mixtures

AimsCultivar mixtures can increase productivity through complementarity in resource use, but reported results are often conflicting and the role of plasticity in shaping plant-plant interactions is poorly understood. We aim to determine if individual cultivars show different phenotypic responses when grown in a mixture, whether these responses depend on the neighboring cultivar identity, and how they contribute to variations in productivity and nitrogen (N) use.MethodsFive spring barley cultivars were field-grown in pure stands and in mixtures during 2 years. Plant traits related to development, growth, N use, and reproduction were measured to identify temporal patterns of plastic responses to neighboring plants.ResultsPlants in mixtures were shorter and developed slower early in the season, but later on they grew faster and produced more grain than the corresponding pure stands. Some cultivars showed complementary N accumulation only when grown together with specific neighbors. Mechanisms of improved productivity differed between the individual mixtures.ConclusionsPlastic plant-plant interaction between cultivars is an important driver behind the variability in mixing effects. Results contribute to a better understanding of how productivity in cultivar mixtures is affected by plastic adaptation and differentiation of plant traits, depending on the environment created by neighboring genotypes.

Herbivore-specific plant volatiles prime neighboring plants for nonspecific defense responses.

Plants produce species-specific herbivore-induced plant volatiles (HIPVs) after damage. We tested the hypothesis that herbivore-specific HIPVs prime neighboring plants to induce defenses specific to the priming herbivore. Since Manduca sexta (specialist) and Heliothis virescens (generalist) herbivory induced unique HIPV profiles in Nicotiana benthamiana, we used these HIPVs to prime receiver plants for defense responses to simulated herbivory (mechanical wounding and herbivore regurgitant application). Jasmonic acid (JA) accumulations and emitted volatile profiles were monitored as representative defense responses since JA is the major plant hormone involved in wound and defense signaling and HIPVs have been implicated as signals in tritrophic interactions. Herbivore species-specific HIPVs primed neighboring plants, which produced 2 to 4 times more volatiles and JA after simulated herbivory when compared to similarly treated constitutive volatile-exposed plants. However, HIPV-exposed plants accumulated similar amounts of volatiles and JA independent of the combination of priming or challenging herbivore. Furthermore, volatile profiles emitted by primed plants depended only on the challenging herbivore species but not on the species-specific HIPV profile of damaged emitter plants. This suggests that feeding by either herbivore species primed neighboring plants for increased HIPV emissions specific to the subsequently attacking herbivore and is probably controlled by JA.

Adult plants facilitate their conspecific seedlings by enhancing arbuscular mycorrhizae in a saline soil

We tested the hypothesis that adult plants can help their conspecific (i.e. an organism belonging to the same species as another organism) seedlings develop symbiosis with arbuscular mycorrhizal fungi (AMF), thereby increasing seedling nutrient uptake and growth in a saline soil. Using the halophytic shrub Tamarix chinensis as a model plant, we conducted two field experiments and a greenhouse experiment. Field experiment 1 assessed the importance of below-ground effects of adult neighbor. Field experiment 2 determined the involvement of AMF in neighbor effects by applying fungicide benomyl to obtain AMF suppressed treatment. The greenhouse experiment tested whether neighbor effects were influenced by AMF hyphal connection between adults and seedlings by using 25 μm and 0.45 μm nylon mesh to allow and prevent the AMF hyphae pass through respectively. Adult neighbor increased shoot biomass and nutrient of target seedlings and the below-ground effects mediated by AMF was facilitative under high soil salinity level. Field experiment 1 showed that adult neighbors reduced soil salinity, increased soil organic matter, and provided AMF spores for target seedlings via whole plant effects or below-ground effects alone. Field experiment 2 showed that shoot biomass and AMF colonization of target seedlings were greater with an adult neighbor when AMF were not suppressed treatment than in AMF were suppressed or there were no neighbors. In the greenhouse experiment, adult neighbors with AMF hyphal connection increased shoot biomass, AMF colonization, and 15N content of target seedlings under the high salinity level. The results support our hypothesis that adult plants can promote the growth and nutrient uptake of their conspecific seedlings in a saline soil by helping them to develop AMF symbiosis. These findings highlight the roles of adult neighbor plants on seedlings regeneration through rhizospheric symbiosis in stressful environments.

Allelopathic Plants: Models for Studying Plant-Interkingdom Interactions.

Allelopathy is a biochemical interaction between plants in which a donor plant releases secondary metabolites, allelochemicals, that are detrimental to the growth of its neighbours. Traditionally considered as bilateral interactions between two plants, allelopathy has recently emerged as a cross-kingdom process that can influence and be modulated by the other organisms in the plant's environment. Here, we review the current knowledge on plant-interkingdom interactions, with a particular focus on benzoxazinoids. We highlight how allelochemical-producing plants influence not only their plant neighbours but also insects, fungi, and bacteria that live on or around them. We discuss challenges that need to be overcome to study chemical plant-interkingdom interactions, and we propose experimental approaches to address how biotic and chemical processes impact plant health.

The Landscape Genetic Signature of Pollination by Trapliners: Evidence From the Tropical Herb, Heliconia tortuosa

Animal-mediated pollination is essential for the maintenance of plant reproduction, especially in tropical ecosystems, where pollination networks have been thought to have highly generalized structures. However, accumulating evidence suggests that not all floral visitors provide equally effective pollination services, potentially reducing the number of realized pollinators and increasing the cryptic specialization of pollination networks. Thus, there is a need to understand how different functional groups of pollinators influence pollination success. Here, we examined whether patterns of contemporary pollen-mediated gene flow in Heliconia tortuosa are consistent with the foraging strategy of its territorial or traplining hummingbird pollinators. Territorial hummingbirds defend clumps of flowers and are expected to transfer pollen locally. In contrast, traplining hummingbirds forage across longer distances, thereby increasing pollen flow among forest fragments, and are thought to repeatedly visit particular plants. If trapliners indeed visit the same plants repeatedly along their regular routes, this could lead to a situation where neighboring plants sample genetically distinct pollen pools. To test this hypothesis, we genotyped 720 seeds and 71 mother plants from 18 forest fragments at 11 microsatellite loci. We performed TwoGener analysis to test pollen pool differentiation within sites (among neighboring plants within the same forest fragment: Φ SC) and between sites (among forest fragments: Φ CT). We found strong, statistically significant pollen pool differentiation among neighboring mother plants (Φ SC = 0.0506), and weaker, statistically significant differentiation among sites (Φ CT = 0.0285). We interpret this pattern of hierarchical pollen pool differentiation as the landscape genetic signature of the foraging strategy of traplining hummingbirds, where repeatable, long-distance, and high-fidelity routes transfer pollen among particular plants. Although H. tortuosa is also visited by territorial hummingbirds, our results suggest that these pollinators do not contribute substantially to successful pollination, highlighting differences in realized pollination efficiency. This cryptic reduction in the number of realized pollinators potentially increases the vulnerability of pollination success to the decline of populations of traplining hummingbirds, which have been shown to be sensitive to forest fragmentation. We conclude that maintaining habitat connectivity to sustain the foraging routes of trapliners may be essential for the maintenance of pollen-mediated gene flow in human-modified landscapes.

Aboveground Competition and Herbivory Overpower Plant-Soil Feedback Contributions to Succession in a Remediated Grassland

Plant-soil feedback (PSF) can provide a driving force during ecological succession by altering soil properties in ways that benefit or disadvantage other species in the successional sequence. Succession may be inevitable in disturbed sites remediated by planting early successional species, but information on PSF in such settings is lacking. We investigated whether gray birch (Betula populifolia), a native pioneer tree, alters succession from grassland to deciduous forest at a site contaminated with zinc, lead, and cadmium. We investigated PSF within the context of competition, herbivory, and soil contaminants, and evaluated whether gray birch, as a metal accumulator, engages in elemental allelopathy, poisoning other species through its metal-contaminated leaf litter. We assessed effects of gray birch on neighboring plant community structure, soil chemistry, fungal root symbionts, and germination, growth, and herbivory of seedlings of black oak (Quercus velutina) and sugar maple (Acer saccharum), two tree species expected to follow gray birch in succession. Gray birch was associated with increased diversity in its neighborhood grassland community, increased herbivory on black oak seedlings, and influenced root fungal colonization in both species. Seedling biomass was correlated with colonization by ectomycorrhizal fungi in black oak, but not with arbuscular mycorrhizal or dark septate fungal colonization in sugar maple. Gray birch had no effect on maple seedling performance or soil chemistry, and a small effect on oak performance in the absence of aboveground competition. We found little evidence consistent with elemental allelopathy. Oak and maple seedlings responded more strongly to variation in soil nutrients than heavy metals, and maintained leaf metal concentration profiles markedly different from those in soils. We conclude that gray birch alters its environment in ways that could promote establishment and succession of woody species, potentially favoring ectomycorrhizal species, but most effects of PSF are overpowered by aboveground competition, herbivory, and/or existing soil factors. This study well illustrates why potential PSF effects on plant performance and community structure must be examined within the context of other ecological processes. Such a broad understanding can inform decisions made in remediation and management of disturbed sites, and our understanding of plant succession and coexistence in general.

Influences of plant interspecific competition and arbuscular mycorrhizal fungi on nitrogen form preference of an invasive plant

Invasive plant species are often able to alter soils in a way that benefits their own fitness over that of native species. While interspecific competitions may drive species to acquire different forms of nitrogen (N) to avoid intensive competition, plant-mycorrhizal interactions can also influence plant nutrient acquisition. Yet, it is unclear whether a variation in N acquisition by an invasive species is driven by interspecific resource partitioning due to competition with native species or by its symbiosis with arbuscular mycorrhizal (AM) fungi. We conducted a pot experiment to examine the effects of competition and fungicide on the uptake of different N forms by Flaveria bidentis, an invasive plant having symbiotic relationships with AM fungi, and two coexisting native species, mycotrophic Bidens maximowicziana and non-mycotrophic Amaranthus retroflexus (referred to by genus hereafter), by growing them either in two-species mixtures or in monocultures. We found that the growth of Flaveria was suppressed by its association with AM fungi regardless of the presence of competing native species, but the degree of suppression was related to the native species with which Flaveria competed. When growing in monocultures, all three species showed a strong preference for NO3−-N over NH4+-N and glycine-N regardless of mycorrhizal status. However, under competition conditions, Flaveria increased 15N recovery in any form of N available (in particular NH4+-15N), depending on neighboring plant identity and AM fungi association, whereas Amaranthus specially tended to decrease NH4+-15N uptake when competing with Flaveria, suggesting a niche complementarity in the utilization of N between two species. Our findings suggested that AM fungi may have the potential to limit the invasion of Flaveria, in the short term, and that interspecific competition plays an important role in partitioning soil N acquisition between plant species.

Competitive effects and responses of the invasive grass Eragrostis plana in Río de la Plata grasslands

AbstractThe ability of an invasive species to establish is mostly determined by its biotic interactions with native species from the recipient community. Here, we evaluate the competitive effects and responses of the invasive Eragrostis plana when interacting with native species, in order to identify possible mechanisms driving invasion in Río de la Plata grasslands. A pairwise competition experiment was performed consisting of treatments that varied in the identity of neighbour plant species: (i) control (no interaction); (ii) intraspecific interaction; (iii) interspecific interaction between native and invasive species; and (iv) interspecific interaction between two co‐occurring native species. Data analysis was separated into the effect of E. plana on the performance of three native perennial grasses (target species: Aristida laevis, Eragrostis neesii and Paspalum notatum) and the response of E. plana to natives (target species: E. plana). Separately for each target species, components of plant performance were compared between neighbouring species treatments. We found that the strength of competitive interactions depended on both target and neighbour species identity. Regarding natives, interspecific competition was stronger than intraspecific. Native species showed distinctive responses to whether the neighbour was the invasive or a co‐occurring native (Eragrostis lugens). Competition between E. plana and native species was stronger than between co‐occurring natives. We demonstrated E. plana had a greater negative effect on native's species performance than the native congener E. lugens. Regarding E. plana, intraspecific competition was stronger than interspecific, and its response was positive or neutral when interacting with natives, suggesting its high tolerance to grow in competition with neighbours. We conclude E. plana's negative effects on native species performance, and its positive or neutral responses to neighbouring native plants demonstrate its strong competitive ability in the recipient community. This may explain its invasion success in southern Brazil and in the encompassing Río de la Plata grasslands.Abstract in Spanish is available with online material.

What five insects told us about how a native plant copes with real-world problems

What five insects told us about how a native plant copes with real-world problems

Towards a framework for collective behavior in growth-driven systems, based on plant-inspired allotropic pairwise interactions

A variety of biological systems are not motile, but sessile in nature, relying on growth as the main driver of their movement. Groups of such growing organisms can form complex structures, such as the functional architecture of growing axons, or the adaptive structure of plant root systems. These processes are not yet understood, however the decentralized growth dynamics bear similarities to the collective behavior observed in groups of motile organisms, such as flocks of birds or schools of fish. Equivalent growth mechanisms make these systems amenable to a theoretical framework inspired by tropic responses of plants, where growth is considered implicitly as the driver of the observed bending towards a stimulus. We introduce two new concepts related to plant tropisms: point tropism, the response of a plant to a nearby point signal source, and allotropism, the growth-driven response of plant organs to neighboring plants. We first analytically and numerically investigate the 2D dynamics of single organs responding to point signals fixed in space. Building on this we study pairs of organs interacting via allotropism, i.e. each organ senses signals emitted at the tip of their neighbor and responds accordingly. In the case of local sensing we find a rich state-space. We describe the different states, as well as the sharp transitions between them. We also find that the form of the state-space depends on initial conditions. This work sets the stage towards a theoretical framework for the investigation and understanding of systems of interacting growth-driven individuals.

The effect of shade levels on the survival and growth of planted trees in dry afromontane forest: Implications for restoration success

Understanding the growth response of different species to canopy gaps will lead to a further perception of species differentiation. Many experimental studies have shown that seedlings can benefit from neighboring plants due to reduced abiotic stress, increased availability of nutrients or reduced herbivorous pressure. Accordingly, this study assessed the differences in survival, root collar diameter (RCD), and height (H) growth of planted seedlings in Desa'a dry afromontane forest, Northern Ethiopia. Seedlings were planted in a random block design with three treatments: canopy cover, artificial shading, and tree species. The canopy cover density had three treatment levels (Open (37%), Medium (51%), and Dense (67%)), artificial shading had two levels (with or without), and tree species had three levels (Dodonea angustifolia Vahl., Olea europaea sub spp. cuspidata, and Juniperus procera Hochst). This study concluded that protection has contributed to the success of the early establishment of seedlings so it should be taken as a prerequisite in enrichment planting programs until seedlings are no more endangered for their establishment. Also, the success of an early seedling establishment with artificial shading and nursery trees implies the need to establish the optimal shading range, which is an important consideration for the success of enrichment activities.

Production of pyrrolizidine alkaloids and shikonins in Echium plantagineum L. in response to various plant stressors.

Echium plantagineum, a native of Europe and Africa, is a noxious invasive weed in Australia forming monocultural stands in pastures and rangelands. It produces a complex mixture of bioactive secondary metabolites, including toxic pyrrolizidine alkaloids (PAs), that protect the plant from insect and livestock herbivory and naphthoquinones (NQs), which suppress competition from weeds, insects and pathogens, and also influence invasion success. However, the extent to which allelochemical production is impacted by environmental factors, thereby influencing plant defense against pests, remains unclear. Following plant stress induced by drought, herbivory and high temperature, extracts of E. plantagineum shoots and roots were subjected to metabolic profiling by UPLC-MS-DAD- QToF mass spectrometry. Abundance of NQs, especially deoxyshikonin, shikonin and dimethylacrylshikonin, rapidly increased in roots exposed to elevated temperatures. Water withholding initially increased NQ abundance, but prolonged drought resulted in reduced total PAs and NQs. Intraspecific competition elevated the production of NQs, whereas simulated herbivory had no initial effect on NQs. Following herbivory, the abundance of the PA 3'-O-acetylechimidine-N-oxide in seedling shoots was increased. Differential accumulation of defense metabolites by E. plantagineum following exposure to various stressors suggested stress-dependent biosynthetic regulation, particularly with respect to NQ production, which was rapidly induced following drought, intraspecific competition and high temperature treatment, thereby positively impacting resistance or defense against herbivores, weeds and pathogens. We propose that trade-offs between above- and below-ground metabolism in E. plantagineum may facilitate allelochemical production in response to stress, rendering plants with an enhanced ability to defend against other neighboring plants, insects and microbes, with allelochemical production further facilitated by catabolic recycling following lengthier exposure to stress. © 2019 Society of Chemical Industry.

Allelochemicals and Signaling Chemicals in Plants

Plants abound with active ingredients. Among these natural constituents, allelochemicals and signaling chemicals that are released into the environments play important roles in regulating the interactions between plants and other organisms. Allelochemicals participate in the defense of plants against microbial attack, herbivore predation, and/or competition with other plants, most notably in allelopathy, which affects the establishment of competing plants. Allelochemicals could be leads for new pesticide discovery efforts. Signaling chemicals are involved in plant neighbor detection or pest identification, and they induce the production and release of plant defensive metabolites. Through the signaling chemicals, plants can either detect or identify competitors, herbivores, or pathogens, and respond by increasing defensive metabolites levels, providing an advantage for their own growth. The plant-organism interactions that are mediated by allelochemicals and signaling chemicals take place both aboveground and belowground. In the case of aboveground interactions, mediated air-borne chemicals are well established. Belowground interactions, particularly in the context of soil-borne chemicals driving signaling interactions, are largely unknown, due to the complexity of plant-soil interactions. The lack of effective and reliable methods of identification and clarification their mode of actions is one of the greatest challenges with soil-borne allelochemicals and signaling chemicals. Recent developments in methodological strategies aim at the quality, quantity, and spatiotemporal dynamics of soil-borne chemicals. This review outlines recent research regarding plant-derived allelochemicals and signaling chemicals, as well as their roles in agricultural pest management. The effort represents a mechanistically exhaustive view of plant-organism interactions that are mediated by allelochemicals and signaling chemicals and provides more realistic insights into potential implications and applications in sustainable agriculture.

Spatial Distribution of Roots across Three Dryland Ecosystems and Plant Functional Types

Roots play a critical role in carbon storage, carbon cycling, and resource acquisition in dryland ecosystems, yet their distribution and production patterns are poorly understood. We aimed to compare the vertical and horizontal distribution of roots of the dominant plant functional types across 3 dryland ecosystems in the western Great Plains of the United States. We collected consecutive soil cores from directly under plants to 29 cm away from the center of plant individuals (horizontal plane), to a 20-cm depth (vertical plane). Across the 3 ecosystem types, grass root biomass decreased with depth and, for the sagebrush steppe, at a distance beyond 6.5 cm from the center of the plant. At the 10–20 cm depth increment, there was no horizontal pattern in root biomass. Uniformity in root biomass in the 10–20 cm depth and at distances >6.5 cm from the plant center is best explained by the overlap of roots of individual and neighboring plants to maximize belowground resource uptake. There was much lower root biomass in the surface 20 cm adjacent to shrubs than adjacent to grasses in the sagebrush steppe, and while grass root biomass decreased significantly with depth and distance as described above, shrub roots were uniform in both planes. Our study confirms that root distribution in drylands differs among plant functional types, with grasses exploiting surface soils both horizontally and vertically to capitalize on surface resources, and shrubs capitalizing less on those resources.

Density-Dependent Plant-Plant Interactions Triggered by Grazing.

Plant species performance in rangelands highly depends on the effect of grazing and also on the occurrence of unpalatable benefactor species that can act as biotic refuges protecting neighboring plants from herbivores. The balance between facilitation and competition may changes with the benefactor density. Despite the high number of studies on the role of biotic refuges, the density dependent effects of unpalatable herbaceous plants on the performance of other species, and on the habitat heterogeneity of rangelands are still unclear. Therefore, we performed a study to test the following hypotheses: (i) Performances of understory species follow a humped-back relationship along the density gradient of the unpalatable benefactor species. (ii) Small-scale heterogeneity of the vegetation decreases with increasing benefactor density. We studied meadow steppes with medium intensity cattle grazing in Hungary. We surveyed understory species’ performance (number of flowering shoots and cover scores) along the density gradient of a common, native unpalatable species (Althaea officinalis). Our findings supported both hypotheses. We found unimodal relationship between the benefactor cover and both the flowering success and richness of understory species. Moreover, small-scale heterogeneity declined with increasing benefactor cover. In this study we detected a humped-back pattern of facilitation along the density gradient of an herbaceous benefactor in pastures. Indeed, this pattern was predictable based on such conceptual models like “consumer pressure-abiotic stress model,” “humped-back model,” “intermediate disturbance hypothesis,” and “disturbance heterogeneity model”; but until now the validity of these relationships has not been demonstrated for herbaceous species. By the demonstration of this effect between herbaceous species we can better forecast the responses of grasslands to changes in management.

On the Ecology of Selenium Accumulation in Plants.

Plants accumulate and tolerate Se to varying degrees, up to 15,000 mg Se/kg dry weight for Se hyperaccumulators. Plant Se accumulation may exert positive or negative effects on other species in the community. The movement of plant Se into ecological partners may benefit them at low concentrations, but cause toxicity at high concentrations. Thus, Se accumulation can protect plants against Se-sensitive herbivores and pathogens (elemental defense) and reduce surrounding vegetation cover via high-Se litter deposition (elemental allelopathy). While hyperaccumulators negatively impact Se-sensitive ecological partners, they offer a niche for Se-tolerant partners, including beneficial microbial and pollinator symbionts as well as detrimental herbivores, pathogens, and competing plant species. These ecological effects of plant Se accumulation may facilitate the evolution of Se resistance in symbionts. Conversely, Se hyperaccumulation may evolve driven by increasing Se resistance in herbivores, pathogens, or plant neighbors; Se resistance also evolves in mutualist symbionts, minimizing the plant’s ecological cost. Interesting topics to address in future research are whether the ecological impacts of plant Se accumulation may affect species composition across trophic levels (favoring Se resistant taxa), and to what extent Se hyperaccumulators form a portal for Se into the local food chain and are important for Se cycling in the local ecosystem.

Evaluation of contaminants spreading from sludge piles, applying geochemical fractionation and attenuation of concentrations model in a tropical reservoir

Drinking water production may generate significant amounts of sludge, which may be contaminated with various metals. For the first time, the mobility/lability of contaminants from two water treatment sludge piles in the Juturnaíba Reservoir was evaluated by applying two geochemical approaches: sequential extractions and attenuation of concentrations model. Both procedures were applied to evaluate the mobility/lability of Al, Cr, Cu, Fe, Mn, and Zn on samples collected in the sludge piles and in the neighborhood of both water treatment plants. The results show that aluminum presents considerably higher concentrations in the sediments close to the sludge piles, with more labile phases; however, the attenuation of concentrations model indicates little spreading of this contaminant in the reservoir. Manganese was shown to be severely depleted in the sludge, indicating that it can be leached away, due to the reducing conditions of the pile. The other elements showed low concentrations and were shown not to affect the concentrations in the reservoir. While the geochemical fractionation indicates the possibility of dissolution to the water column, the attenuation of concentrations model gives information on the spatial dispersion of the contaminants, constituting interesting complementary approaches.