scholarly journals Can aphids be controlled by fungus? A mathematical model

2019 ◽  
Vol 4 (1) ◽  
pp. 79-92
Author(s):  
Nicholas F. Britton ◽  
Iulia Martina Bulai ◽  
Stéphanie Saussure ◽  
Niels Holst ◽  
Ezio Venturino
Keyword(s):  
Steady State ◽  
Plant Biomass ◽  
Insect Pests ◽  
Fungal Spores ◽  
Pathogen Transmission ◽  
Trophic Levels ◽  
Aphid Population ◽  
Biomass Equation ◽  
Transmission Parameters ◽  
Set Up

AbstractThe control of insect pests in agriculture is essential for food security. Chemical controls typically damage the environment and harm beneficial insects such as pollinators, so it is advantageous to identify targetted biological controls. Since predators are often generalists, pathogens or parasitoids are more likely to serve the purpose. Here, we model a fungal pathogen of aphids as a potential means to control of these important pests in cereal crops. Typical plant herbivore pathogen models are set up on two trophic levels, with dynamic variables the plant biomass and the uninfected and infected herbivore populations. Our model is unusual in that (i) it has to be set up on three trophic levels to take account of fungal spores in the environment, but (ii) the aphid feeding mechanism leads to the plant biomass equation becoming uncoupled from the system. The dynamical variables are therefore the uninfected and infected aphid population and the environmental fungal concentration. We carry out an analysis of the dynamics of the system. Assuming that the aphid population can survive in the absence of disease, the fungus can only persist (and control is only possible) if (i) the host grows sufficiently strongly in the absence of infection, and (ii) the pathogen transmission parameters are sufficiently large. If it does persist the fungus does not drive the aphid population to extinction, but controls it below its disease-free steady state value, either at a new coexistence steady state or through oscillations. Whether this control is sufficient for agricultural purposes will depend on the detailed parameter values for the system.

scholarly journals Application of UV-C Irradiation to Rosa x hybrida Plants as a Tool to Minimise Macrosiphum rosae Populations

Agronomy ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 702
Author(s):  
Anastasios I. Darras ◽  
Panagiotis J. Skouras ◽  
Panagiotis Assimomitis ◽  
Chara Labropoulou ◽  
George J. Stathas
Keyword(s):  
Host Resistance ◽  
Insect Pests ◽  
Physiological Responses ◽  
Co2 Assimilation ◽  
Aphid Population ◽  
First Instar ◽  
Net Co2 Assimilation ◽  
Macrosiphum Rosae ◽  
Uv C ◽  
Aphid Fecundity

UV-C irradiation is known to enhance plant resistance against insect pests. In the present study, we evaluated the effects of low doses of UV-C on Macrosiphum rosae infesting greenhouse rose (Rosa x hybrida) plants. The application of 2.5-kJ/m2 UV-C irradiation on rose leaves before infestation induced anti-herbivore resistance and negatively affected the aphid fecundity. No eggs and first instar nymphs were recorded on irradiated leaves, whereas an average of 4.3 and 2.7 eggs and 6.7 and 14 first instars were recorded on vars. “Etoile Brilante” and “Arlen Francis” untreated leaves, respectively. UV-C irradiation reduced the aphid population from naturally infested rose plants by up to 58%. In a greenhouse pot trial (GPT) in 2019, UV-C irradiation minimised the initial aphid population six hours after treatment. UV-C elicited host resistance and, also, helped in aphid repulsion without killing the adult individuals. UV-C did not affect the physiological responses of rose plants. The net CO2 assimilation of the UV-C irradiated plants ranged between 10.55 and 15.21 μmol/m2. sec for “Arlen Francis” and between 10.51 and 13.75 μmol/m2. sec for “Etoile Brilante” plants. These values, with only a few exceptions, were similar to those recorded to the untreated plants.

Zooplankton growth and survival differentially respond to interactive warming and acidification effects

2020 ◽  
Vol 42 (2) ◽  
pp. 189-202
Author(s):  
Jessica Garzke ◽  
Ulrich Sommer ◽  
Stefanie M H Ismar-Rebitz
Keyword(s):  
Ocean Acidification ◽  
Single Species ◽  
Functional Trait ◽  
Trophic Levels ◽  
Growth And Survival ◽  
Geographical Regions ◽  
Wide Range ◽  
Set Up ◽  
Taxonomic Groups ◽  
Zooplankton Growth

Abstract The copepod Acartia tonsa is a key component of a wide range of marine ecosystems, linking energy transfer from phytoplankton to higher trophic levels, and has a central role in productivity and biogeochemistry. The interaction of end-of-century global warming and ocean acidification scenarios with testing moderate temperature effects on a seminatural copepod community is needed to understand future community functioning. Here, we deployed a mesocosm experimental set-up with a full factorial design using two temperatures (13°C and 19°C) crossed with a pCO2 gradient ranging from ambient (550 μatm) to 3000 μatm. We used the natural bacteria, phyto- and microzooplankton species composition and biomass of the Kiel Bight and tested the response of A. tonsa development, carbon growth, mortality, size and condition. The tested traits were differently affected by the interaction of temperature and acidification. Ocean acidification increased development, carbon growth, size and mortality under the warming scenario of 19°C. At 13°C mortality rates decreased, while carbon growth, size and condition increased with acidification. We conclude from our experimental approach that a single species shows a variety of responses depending on the focal functional trait. Trait-specific mesozooplankton responses need to be further investigated and compared between geographical regions, seasons and taxonomic groups.

scholarly journals Soil and plant communities development and ecological effectiveness of reclamation on a sand mine cast

2008 ◽  
Vol 54 (No. 12) ◽  
pp. 554-565 ◽  
Author(s):  
M. Pietrzykowski
Keyword(s):  
Plant Biomass ◽  
Terrestrial Ecosystem ◽  
Soil Characteristics ◽  
Carbon Accumulation ◽  
Nitrogen Accumulation ◽  
Ecosystem Development ◽  
Spontaneous Succession ◽  
Forest Reclamation ◽  
Set Up

The aim of the study was to assess terrestrial ecosystem development (mainly vegetation and soil characteristics) in the area of a sand mine cast (located in southern Poland) that has been either reclaimed or left for natural succession. A total of 20 sites in a chronosequence of 5, 17, 20 and 25 years were set up in two site categories: reclaimed and non-reclaimed sites. Selected properties of initial soils and features of vegetation were measured and they included carbon accumulation in soil; biomass and diversity of communities were also estimated. Next, based on carbon accumulation, the energy trapped in ecosystem components was estimated. Although the results of plant community investigation did not show the same distinct differences between site categories, the case study suggests that reclamation significantly accelerates ecosystem development. In comparison with spontaneous succession, the complete forest reclamation was found to increase the amount of carbon accumulation, thickness of humus horizon, and energy trapped in soil organic carbon and plant biomass in the developing ecosystem 2–3 times and nitrogen accumulation 5 times.

scholarly journals Review of Copper and Copper Nanoparticle Toxicity in Fish

Nanomaterials ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 1126 ◽  
Author(s):  
Nemi Malhotra ◽  
Tzong-Rong Ger ◽  
Boontida Uapipatanakul ◽  
Jong-Chin Huang ◽  
Kelvin H.-C. Chen ◽  
...  
Keyword(s):  
Metal Ions ◽  
Metallic Nanoparticles ◽  
Copper Complexes ◽  
Fungal Spores ◽  
Aquatic Organisms ◽  
Trophic Levels ◽  
Water Bodies ◽  
Copper Metal ◽  
Physiochemical Parameters ◽  
Toxicity Mechanisms

This review summarizes the present knowledge on the toxicity of copper and copper nanoparticles (CuNPs) to various fish species. In previous decades, the excessive usage of metal and metallic nanoparticles has increased significantly, increasing the probability of the accumulation and discharge of metals in various trophic levels of the environment. Due to these concerns, it is important to understand the toxicity mechanisms of metals and metallic nanoparticles before they lead to unhealthy effects on human health. In this review paper, we specifically focus on the effect of metal copper and CuNPs on different fish organs under different physiochemical parameters of various water bodies. Nowadays, different forms of copper have distinctive and specific usages, e.g., copper sulfate is a well-established pesticide which is used to control the growth of algae in lakes and ponds. Deactivating the fungi enzymes prevents fungal spores from germinating. This process of deactivation is achieved via the free cupric ions, which are established as the most toxic forms of copper. Complexes of copper with other ligands may or may not be bioavailable for use in aquatic organisms. On the other hand, CuNPs have shown cost-effectiveness and numerous promising uses, but the toxicity and availability of copper in a nanoparticle form is largely unknown, Additionally, physiochemical factors such as the hardness of the water, alkalinity, presence of inorganic and organic ligands, levels of pH, and temperature in various different water bodies affect the toxicity caused by copper and CuNPs. However, comprehensive knowledge and data regarding the pattern of toxicity for copper metal ions and CuNPs in marine organisms is still limited. In this review, we carry out a critical analysis of the availability of the toxicological profiles of copper metal ions and CuNPs for different fishes in order to understand the toxicity mechanisms of copper and CuNPs. We believe that this review will provide valuable information on the toxicological profile of copper, which will further help in devising safe guidelines for the usage of copper and CuNPs in a sustainable manner.

scholarly journals Invasive nosocomial pulmonary aspergillosis: risk factors and hospital building works

1987 ◽  
Vol 99 (2) ◽  
pp. 407-412 ◽  
Author(s):  
M. Perraud ◽  
M. A. Piens ◽  
N. Nicoloyannis ◽  
P. Girard ◽  
M. Sepetjan ◽  
...  
Keyword(s):  
Risk Factors ◽  
Epidemiological Study ◽  
Fungal Spores ◽  
Invasive Pulmonary Aspergillosis ◽  
Pulmonary Aspergillosis ◽  
Protective Measures ◽  
Insulation Materials ◽  
Acoustic Insulation ◽  
Hospital Building ◽  
Set Up

SUMMARYA retrospective epidemiological study of 22 observations of invasive pulmonary aspergillosis, of which 18 were fatal, occurring over a period of 30 months, implicated certain building sites within the hospital. The building works were responsible for the diffusion into the atmosphere of fungal spores from normally closed reservoirs, notably false ceilings, fibrous thermal and/or acoustic insulation materials and roller-blind casings. The results of our study permit us to suggest that protective measures should be set up or that immunodepressed patients are evacuated when such works are to be carried out in an in-patient establishment.

scholarly journals Bacteriophage Migration via Nematode Vectors: Host-Parasite-Consumer Interactions in Laboratory Microcosms

2006 ◽  
Vol 72 (3) ◽  
pp. 1974-1979 ◽  
Author(s):  
John J. Dennehy ◽  
Nicholas A. Friedenberg ◽  
Yul W. Yang ◽  
Paul E. Turner
Keyword(s):  
Experimental Studies ◽  
Virus Transmission ◽  
Growth Dynamics ◽  
Model System ◽  
Pathogen Transmission ◽  
Trophic Levels ◽  
Future Research ◽  
Evolution Of Virulence ◽  
Consumer Interactions ◽  
Host Parasite

ABSTRACT Pathogens vectored by nematodes pose serious agricultural, economic, and health threats; however, little is known of the ecological and evolutionary aspects of pathogen transmission by nematodes. Here we describe a novel model system with two trophic levels, bacteriophages and nematodes, each of which competes for bacteria. We demonstrate for the first time that nematodes are capable of transmitting phages between spatially distinct patches of bacteria. This model system has considerable advantages, including the ease of maintenance and manipulation at the laboratory bench, the ability to observe many generations in short periods, and the capacity to freeze evolved strains for later comparison to their ancestors. More generally, experimental studies of complex multispecies interactions, host-pathogen coevolution, disease dynamics, and the evolution of virulence may benefit from this model system because current models (e.g., chickens, mosquitoes, and malaria parasites) are costly to maintain, are difficult to manipulate, and require considerable space. Our initial explorations centered on independently assessing the impacts of nematode, bacterium, and phage population densities on virus migration between host patches. Our results indicated that virus transmission increases with worm density and host bacterial abundance; however, transmission decreases with initial phage abundance, perhaps because viruses eliminate available hosts before migration can occur. We discuss the microbial growth dynamics that underlie these results, suggest mechanistic explanations for nematode transmission of phages, and propose intriguing possibilities for future research.

Microstructure Evolution of Ti-Al Peritectic System during the Initiated Stage of Directional Solidification

2007 ◽  
Vol 546-549 ◽  
pp. 1447-1450 ◽  
Author(s):  
Yan Qing Su ◽  
Chang Liu ◽  
Xin Zhong Li ◽  
Jing Jie Guo ◽  
Heng Zhi Fu
Keyword(s):  
Steady State ◽  
Directional Solidification ◽  
Microstructure Evolution ◽  
Aluminum Content ◽  
Solid Phase ◽  
Tial Alloys ◽  
Transient Stage ◽  
Set Up ◽  
Solid Liquid Interface ◽  
Solid Liquid

The microstructure evolution of Ti-Al peretectic system in transient stage and steady state in directional solidification was predicted via theoretical analysis. The solute distribution controlled by diffusion at and ahead the solid-liquid interface will determine whether the properitectic and peritectic phases can nucleate and grow ahead of the opposing solid phase. The formation of banding structure is possible in a certain composition range. At the steady state, a microstructure selection map was set up based on interface response function model. The microstructure of TiAl alloys with different aluminum content was studied with Bridgman directional solidification method. Some evidence in the experiment has been found to support the theoretical prediction.

Modeling mercury cycling in the marine environment

2020 ◽  
Author(s):  
Johannes Bieser ◽  
Ute Daewel ◽  
Corinna Schrum
Keyword(s):  
Numerical Models ◽  
Marine Ecosystem ◽  
Ecosystem Model ◽  
Trophic Levels ◽  
Modeling Framework ◽  
Modeling Tools ◽  
Large Variability ◽  
Marine Ecosystem Model ◽  
Set Up ◽  
Fully Coupled

<p>Five decades of Hg science have shown the <strong>tremendous complexity of the global Hg cycle</strong>. Yet, the pathways that lead from anthropogenic Hg emissions to MeHg exposure through sea food are not fully comprehended. Moreover, the observed amount of MeHg in fish exhibits a large temporal and spatial variability that we cannot predict yet. A key issue is that fully speciated Hg measurements in the ocean are difficult to perform and thus we will never be able to achieve a comprehensive spatial and temporal coverage.</p><p>Therefore, we need complex modeling tools that allow us to fill the gaps in the observations and to predict future changes in the system under changing external drivers (emissions, climate change, ecosystem changes). Numerical models have a long history in Hg research, but so far have virtually only addressed inorganic Hg cycling in atmosphere and oceans.</p><p>Here we present a novel 3d-hydrodynamic mercury modeling framework based on fully coupled compartmental models including atmosphere, ocean, and ecosystem. The generalized high resolution model has been set up for European shelf seas and was used to model the transition zone from estuaries to the open ocean. Based on this model we present our findings on intra- and inter-annual dynamics and variability of mercury speciation and distribution in a coastal ocean. Moreover, we present the first results on the dynamics of mercury bio-accumulation from a fully coupled marine ecosystem model. Most importantly, the model is able to reproduce the large variability in methylmercury accumulation in higher trophic levels.</p>

Plankton ecology and the Proterozoic-Phanerozoic transition

Paleobiology ◽  
1997 ◽  
Vol 23 (2) ◽  
pp. 247-262 ◽  
Author(s):  
Nicholas J. Butterfield
Keyword(s):  
Plant Biomass ◽  
Marine Ecology ◽  
Trophic Levels ◽  
Cambrian Explosion ◽  
Significant Shift ◽  
Early Cambrian ◽  
Cascade Process ◽  
Key Innovation ◽  
Large Animals ◽  
Net Phytoplankton

Most modern marine ecology is ultimately based on unicellular phytoplankton, yet most large animals are unable to graze directly on even relatively large net phytoplankton; the repackaging effected by herbivorous mesozooplankton thus represents a key link in marine metazoan food chains. Despite the deep taphonomic biases affecting plankton fossilization, there is a clear record of phytoplankton from at least 1800 m.y ago. Proterozoic plankton are represented by small-to medium-sized sphaeromorphic acritarchs and probably do not include many/most of the unusually large acritarchs that characterize the Neoproterozoic. The first significant shift in phytoplankton diversity was therefore the rapid radiation of small acanthomorphic acritarchs in the Early Cambrian. The coincidence of phytoplankton diversification with the Cambrian radiation of large animals points compellingly to an ecological linkage between the two, particularly in light of recently discovered filter-feeding mesozooplankton in the Early Cambrian. The introduction of planktic filter feeders would have established the second tier of the Eltonian pyramid, potentially setting off the “self-propagating mutual feedback system of diversification” now recognized as the Cambrian explosion (Stanley 1973, 1976).By consuming significant percentages of net phytoplankton and suspending it as animal biomass and non-aggregating fecal pellets, mesozooplankton cause a net reduction in export production; a general introduction of zooplankton would therefore have reduced carbon burial and moderated the bloom and bust cycle that must have characterized Proterozoic populations of net phytoplankton. The effect of added trophic levels in Early Cambrian ecosystems can be viewed as a serial application of the trophic cascade process observed in modern lakes, whereby the introduction of higher trophic levels determines the accumulation of plant biomass at the base of the system. As such, the major biogeochemical perturbations that mark the onset of the Phanerozoic might be considered a consequence, rather than a cause, of the Cambrian explosion; reduced C export due to zooplankton expansion explains the otherwise anomalous drop in δ13C at the base of the Tommotian.Cambrian acanthomorphic acritarchs likely derived from planktic leiosphaerids exposed to mesozooplanktic grazing pressure, the ornamentation effectively increasing vesicle size without compromising buoyancy or surface-area:volume ratios. Alternatively, they may represent an escape into the plankton through a miniaturization of the much larger Neoproterozoic acanthomorphs. An invasion of small benthic herbivores into the water column to exploit the phytoplankton accounts for the origin of the mesozooplankton and may have been the key innovation in the Cambrian explosion.

Maxwell's Law, and the Absorption and Emission of Radiation

1926 ◽  
Vol 23 (4) ◽  
pp. 465-471 ◽  
Author(s):  
E. A. Milne
Keyword(s):  
Steady State ◽  
Thermodynamic Equilibrium ◽  
Velocity Component ◽  
Radiant Energy ◽  
Mean Square ◽  
Recoil Momentum ◽  
Famous Paper ◽  
The Mean ◽  
Set Up ◽  
Planck’S Law

In the famous paper in which he developed his theory of radiation, Einstein investigated two problems. He investigated first the problem of what distribution of radiant energy in the steady state would be set up by an enclosed assembly of atoms in thermodynamic equilibrium radiating and absorbing according to the assumptions of his theory; he showed that the distribution so set up was given by Planck's law. He investigated secondly the velocities set up amongst the atoms in consequence of the random variations in direction of the emissions and absorptions; provided that emissions are assumed to be directed, so giving rise to recoil momentum, he showed that the mean square velocity-component in a given direction, , is equal to its equipartition value, given by .

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