57 research outputs found
Evidence for an Allelopathic Interaction Between Rye and Wild Oats
Allelopathy is a biological phenomenon in which an organism produces one or more biochemicals that influence the growth, survival, and reproduction of other organisms. Allelopathy has been the subject of a great deal of research in chemical ecology since the 1930s. The characterization of the factors that influence this phenomenon has barely been explored, mainly due to the complexity of this area. The main aim of the research carried out to date has been to shed light on the importance of these interactions in agroecosystems, especially in relation to the interactions between crops and weeds. Herein we report the characterization of a complete allelochemical pathway involving benzoxazinones, which are known to participate in allelopathic plant defense interactions of several plants of high agronomic interest. The production of the defense chemicals by a donor plant (crop), the route and transformations of the chemicals released into the environment, and the uptake and phytotoxic effects on a target plant (weed) were all monitored. The results of this study, which is the first of its kind, allowed a complete dynamic characterization of the allelopathic phenomenon for benzoxazinones
Taking Ecological Function Seriously: Soil Microbial Communities Can Obviate Allelopathic Effects of Released Metabolites
Allelopathy (negative, plant-plant chemical interactions) has been largely studied as an autecological process, often assuming simplistic associations between pairs of isolated species. The growth inhibition of a species in filter paper bioassay enriched with a single chemical is commonly interpreted as evidence of an allelopathic interaction, but for some of these putative examples of allelopathy, the results have not been verifiable in more natural settings with plants growing in soil.On the basis of filter paper bioassay, a recent study established allelopathic effects of m-tyrosine, a component of root exudates of Festuca rubra ssp. commutata. We re-examined the allelopathic effects of m-tyrosine to understand its dynamics in soil environment. Allelopathic potential of m-tyrosine with filter paper and soil (non-sterile or sterile) bioassays was studied using Lactuca sativa, Phalaris minor and Bambusa arundinacea as assay species. Experimental application of m-tyrosine to non-sterile and sterile soil revealed the impact of soil microbial communities in determining the soil concentration of m-tyrosine and growth responses.Here, we show that the allelopathic effects of m-tyrosine, which could be seen in sterilized soil with particular plant species were significantly diminished when non-sterile soil was used, which points to an important role for rhizosphere-specific and bulk soil microbial activity in determining the outcome of this allelopathic interaction. Our data show that the amounts of m-tyrosine required for root growth inhibition were higher than what would normally be found in F. rubra ssp. commutata rhizosphere. We hope that our study will motivate researchers to integrate the role of soil microbial communities in bioassays in allelopathic research so that its importance in plant-plant competitive interactions can be thoroughly evaluated
Interaction of 8-Hydroxyquinoline with Soil Environment Mediates Its Ecological Function
Background: Allelopathic functions of plant-released chemicals are often studied through growth bioassays assuming that these chemicals will directly impact plant growth. This overlooks the role of soil factors in mediating allelopathic activities of chemicals, particularly non-volatiles. Here we examined the allelopathic potential of 8-hydroxyquinoline (HQ), a chemical reported to be exuded from the roots of Centaurea diffusa. Methodology/Principal Findings: Growth bioassays and HQ recovery experiments were performed in HQ-treated soils (non-sterile, sterile, organic matter-enriched and glucose-amended) and untreated control soil. Root growth of either Brassica campestris or Phalaris minor was not affected in HQ-treated non-sterile soil. Soil modifications (organic matter and glucose amendments) could not enhance the recovery of HQ in soil, which further supports the observation that HQ is not likely to be an allelopathic compound. Hydroxyquinoline-treated soil had lower values for the CO2 release compared to untreated non-sterile soil. Soil sterilization significantly influenced the organic matter content, PO 4-P and total organic nitrogen levels. Conclusion/Significance: Here, we concluded that evaluation of the effect of a chemical on plant growth is not enough in evaluating the ecological role of a chemical in plant-plant interactions. Interaction of the chemical with soil factors largel
Serotonin Augments Gut Pacemaker Activity via 5-HT3 Receptors
Serotonin (5-hydroxytryptamine: 5-HT) affects numerous functions in the gut, such as secretion, muscle contraction, and enteric nervous activity, and therefore to clarify details of 5-HT's actions leads to good therapeutic strategies for gut functional disorders. The role of interstitial cells of Cajal (ICC), as pacemaker cells, has been recognised relatively recently. We thus investigated 5-HT actions on ICC pacemaker activity. Muscle preparations with myenteric plexus were isolated from the murine ileum. Spatio-temporal measurements of intracellular Ca2+ and electric activities in ICC were performed by employing fluorescent Ca2+ imaging and microelectrode array (MEA) systems, respectively. Dihydropyridine (DHP) Ca2+ antagonists and tetrodotoxin (TTX) were applied to suppress smooth muscle and nerve activities, respectively. 5-HT significantly enhanced spontaneous Ca2+ oscillations that are considered to underlie electric pacemaker activity in ICC. LY-278584, a 5-HT3 receptor antagonist suppressed spontaneous Ca2+ activity in ICC, while 2-methylserotonin (2-Me-5-HT), a 5-HT3 receptor agonist, restored it. GR113808, a selective antagonist for 5-HT4, and O-methyl-5-HT (O-Me-5-HT), a non-selective 5-HT receptor agonist lacking affinity for 5-HT3 receptors, had little effect on ICC Ca2+ activity. In MEA measurements of ICC electric activity, 5-HT and 2-Me-5-HT caused excitatory effects. RT-PCR and immunostaining confirmed expression of 5-HT3 receptors in ICC. The results indicate that 5-HT augments ICC pacemaker activity via 5-HT3 receptors. ICC appear to be a promising target for treatment of functional motility disorders of the gut, for example, irritable bowel syndrome
A starting guide to root ecology: strengthening ecological concepts and standardising root classification, sampling, processing and trait measurements
In the context of a recent massive increase in research on plant root functions and their impact on the environment, root ecologists currently face many important challenges to keep on generating cutting-edge, meaningful and integrated knowledge. Consideration of the below-ground components in plant and ecosystem studies has been consistently called for in recent decades, but methodology is disparate and sometimes inappropriate. This handbook, based on the collective effort of a large team of experts, will improve trait comparisons across studies and integration of information across databases by providing standardised methods and controlled vocabularies. It is meant to be used not only as starting point by students and scientists who desire working on below-ground ecosystems, but also by experts for consolidating and broadening their views on multiple aspects of root ecology. Beyond the classical compilation of measurement protocols, we have synthesised recommendations from the literature to provide key background knowledge useful for: (1) defining below-ground plant entities and giving keys for their meaningful dissection, classification and naming beyond the classical fine-root vs coarse-root approach; (2) considering the specificity of root research to produce sound laboratory and field data; (3) describing typical, but overlooked steps for studying roots (e.g. root handling, cleaning and storage); and (4) gathering metadata necessary for the interpretation of results and their reuse. Most importantly, all root traits have been introduced with some degree of ecological context that will be a foundation for understanding their ecological meaning, their typical use and uncertainties, and some methodological and conceptual perspectives for future research. Considering all of this, we urge readers not to solely extract protocol recommendations for trait measurements from this work, but to take a moment to read and reflect on the extensive information contained in this broader guide to root ecology, including sections IâVII and the many introductions to each section and root trait description. Finally, it is critical to understand that a major aim of this guide is to help break down barriers between the many subdisciplines of root ecology and ecophysiology, broaden researchersâ views on the multiple aspects of root study and create favourable conditions for the inception of comprehensive experiments on the role of roots in plant and ecosystem functioning
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The Biology of Invasive Alien Plants in Canada. 5. Polygonum cuspidatum Sieb. & Zucc. [= Fallopia japonica (Houtt.) Ronse Decr.]
Polygonum cuspidatum (Japanese knotweed) is an introduced perennial geophyte in the buckwheat family (Polygonaceae). The phytogeographic distribution of P. cuspidatum in North America suggests a large number of intentional introductions via ornamental plantings from 1870 to 2000, followed by secondary spread from these foci. This species is most pernicious along riparian corridors and road and railroad rights-of-way, reducing visibility, displacing native species, negatively affecting native wildlife, and causing alterations in natural hydrologic processes. Although non-hybrid seed recruitment has not been observed in Europe because of the presence of male-sterile clones only, dispersal of seeds and stem and rhizome fragments by flowing water does occur in North America and populations are readily established from these sources. The primary means of local and regional range expansion is human-mediated transport of rhizome-infested soil. Hybridization is common with the congener P. sachalinense in the introduced ranges of North America and Europe resulting in the equally noxious P. Ă bohemicum. Key words: Japanese knotweed, Mexican bamboo, Polygonum, Fallopia, Reynoutria, POLCU, invasive plant, weed biolog
Preferential flow systems amended with biogeochemical components: imaging of a two-dimensional study
The vadose zone is a highly interactive heterogeneous system through which
water enters the subsurface system by infiltration. This paper details the
effects of simulated plant exudate and soil component solutions upon unstable
flow patterns in a porous medium (ASTM silica sand; US Silica, Ottawa, IL,
USA) through the use of two-dimensional tank light transmission method
(LTM). The contact angle (Ξ) and surface tension (γ) of two
simulated plant exudate solutions (i.e., oxalate and citrate) and two soil
component solutions (i.e., tannic acid and Suwannee River natural organic matter, SRNOM) were analyzed to determine the liquidâgas and liquidâsolid
interface characteristics of each. To determine if the unstable flow
formations were dependent on the type and concentration of the simulated
plant exudates and soil components, the analysis of the effects of the
simulated plant exudate and soil component solutions were compared to a
control solution (Hoagland nutrient solution with 0.01Â MÂ NaCl). Fingering
flow patterns, vertical and horizontal water saturation profiles, water
saturation at the fingertips, finger dimensions and velocity, and number of
fingers were obtained using the light transmission method. Significant
differences in the interface properties indicated a decrease between the
control and the plant exudate and soil component solutions tested;
specifically, the control (Ξâ=ââŻ64.5° and Îłâ=ââŻ75.75âŻmNâŻmâ1) samples exhibited a higher contact
angle and surface tension than the low concentration of citrate (Ξâ=ââŻ52.6° and Îłâ=ââŻ70.8âŻmNâŻmâ1). Wetting front
instability and fingering flow phenomena were reported in all infiltration
experiments. The results showed that the plant exudates and soil components
influenced the soil infiltration as differences in finger geometries,
velocities, and water saturation profiles were detected when compared to the
control. Among the tested solutions and concentrations of soil components,
the largest finger width (10.19âŻcm) was generated by the lowest tannic acid
solution concentration (0.1âŻmgâŻLâ1), and the lowest finger width
(6.00âŻcm) was induced by the highest SRNOM concentration (10âŻmgâŻLâ1).
Similarly, for the plant exudate solutions, the largest finger width
(8.36âŻcm) was generated by the lowest oxalate solution concentration
(0.1âŻmgâŻLâ1), and the lowest finger width (6.63âŻcm) was induced by the
lowest citrate concentration (0.1âŻmgâŻLâ1). The control solution
produced fingers with average width of 8.30âŻcm. Additionally, the
wettability of the medium for the citrate, oxalate, and SRNOM solutions
increased with an increase in concentration. Our research demonstrates that
the plant exudates and soil components which are biochemical compounds
produced and released in soil are capable of influencing the process of
infiltration in soils. The results of this research also indicate that soil
wettability, expressed as cosΞ1â2, should be
included in the scaling of the finger dimension, i.e., finger width, when
using the Miller and Miller (1956) scaling theory for the scaling of flow in
porous media
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