Acc Deaminase And The Reduction Of Plant Ethylene

In higher plants, ethylene is produced from L-methionine via the intermediates, S-adenosyl-L-methionine (SAM) and 1-aminocyclopropane-1-carboxylic acid (ACC) 12 . The enzymes involved in this metabolic sequence are SAM synthetase, which catalyzes the conversion of methionine to SAM 13 ACC synthase, which is responsible for the hydrolysis of SAM to ACC and 5-methylthioadenosine 14 and ACC oxidase, which metabolizes ACC to ethylene, carbon dioxide and cyanide 15 . In 1978, an enzyme capable of...

Anaerobic Dechlorination

The observation that PCB contaminated sediments display a higher content of low chlorinated congeners than the mixture at the origin of the contamination was the first clue that anaerobic bacteria are able to degrade PCBs by a reductive dechlorination process. This process has been well documented for several aquatic sediments 30, 31, 32 . Anaerobic enrichment cultures able to dechlorinate PCBs were maintained in laboratory conditions, with and without sediment 33, 34, 35, 36, 37 . The...

Arbuscular Mycorrhizal Fungi

There are relatively scarce data on the effects of soil contamination on field abundance and diversity of populations of AM fungi. It was found that contamination of soils with heavy metals decreased numbers of AM propagules and reduced mycorrhizal infectivity of soils as compared to uncontaminated sites 15, 16, 17 . Nevertheless, spores of the AM fungi and relatively high levels of root colonisation were reported even from highly contaminated mine spoils as well as polluted agricultural soils...

Arbuscular Mycorrhizal Plants

Inoculation with AM fungi has been repeatedly reported to modify HM uptake by host plants, however, the results are contradictory 4, 11 . In general, AM plants are more efficient than non-mycorrhizal in the acquisition of micronutrients such as copper, iron, manganese and zinc when available at low concentrations 57, 58, 59, 60, 61 . However, when grown in excess of micronutrients or in soils contaminated by HMs with unknown biological function such as cadmium, chromium or lead, both...

Cdna Libraries

Numerous enzyme sequences have been identified in Arabidopsis, but little headway has been made in matching specific enzymes with their function on herbicide substrates. Molecular information on enzymes and function identification towards herbicides has been studied based on cDNA libraries. cDNA libraries are prepared from the mRNA of interest that is synthesized to DNA (cDNA) strand, which contains a specific coding region of a genome that is inserted into vectors and cloned 30 . Studies on...

Chlorinated Voc Degradation In Plant Tissues

Plant tissues are also capable of degrading chlorinated solvents. Degradation products of TCE detected in plant tissues include trichloroethanol, trichloroacetic acid, dichloroacetic acid and trichloroethanol glycoside 1, 5, 7, 8, 18-21 . These oxidative metabolites have been identified in controlled cell culture experiments, whole plant laboratory experiments and full-scale field settings. When evaluating oxidative metabolite levels in plants, caution and background sampling should take place...

Containing Gene Flow

Several molecular mechanisms have been suggested for containing gene flow (i.e., to prevent gene flow between the phytoremediating species and relatives), especially by pollen, ignoring the other routes of sporophyte propagule (seeds and asexual parts) movement, especially transgenes within the phytoremediating species (i.e., to prevent outflow to related species), or to mitigate the effects of transgene flow once it has occurred 20, 22, 26, 29 . It is more important to prevent gene flow from...

Decision Trees For Assessing The Level Of Risk

Here we combine the different factors through the use of decision trees. We want to state clearly that a decision tree is not a quantitative tool producing a quantified risk. It is an aid in risk evaluation providing unbiased guidance in indicating hazards attached to a certain species. When a hazard is indicated, more detailed and quantified data acquisition will often be necessary. Different levels of certainty apply to the various factors used. For instance invasiveness is highly...

Ectomycorrhizal Plants

Regarding heavy metal uptake by host plants, EcM fungi can decrease the uptake of range of elements, e.g. aluminium 85 , cadmium 50 , copper 86 , lead 87 and zinc 50 and thus alleviate HM toxicity to the host plants. For example, the seedlings of birch, pine and spruce were reported to be less susceptible to toxic concentrations of zinc, copper, nickel and aluminium when formed associations with several EcM fungi 88 . In another study, Paxillus involutus ameliorated the toxicity of cadmium and...

Field scale contaminant fate and hydraulic control

Full-scale phytoremediation of VOCs has been active at contaminated sites since 1995 and 1996. In the decade since then, findings at the field sites have varied. In part the results are sketchy as some processes that are important were not previously considered and data collection is limited and largely unpublished. The full-scale phytoremediation site at the APG J-field site in Maryland is among the best characterized and analysed. Sampling at the site provided some of the first clear...

Forensic Field Studies

While conventional wisdom may dictate a progression from bench to greenhouse to field-testing of remedial technologies, there are distinct advantages to starting directly in the field to examine the rhizoremediation capabilities of natural vegetation. This approach affords a view of the long-term impacts of a diverse array of plant species, including mature trees, on microbial communities and or contaminant disappearance otherwise inaccessible due to the practical time limitations of most...

Info

In vitro culture and micropropagation Developing cell culture and micropropagation protocols for a diverse group of wetland monocot species was facilitated by the availability of a universal cell culture initiation medium, which had successfully been used for a great number of species 8, 10, 15 . The method comprised using immature inflorescences as explants and cultivating the tissue on a primary medium to produce totipotent embryogenic tissue culture, cultivating the embryogenic tissue on a...

KM

Alternatively, empirical relations exist. The TSCF is related to the KOW 11 by a bell-shaped (Gaussian) curve For poplar trees, a similar relation was found by 12 (corrected by authors) It is recommended to use Briggs' equation (4b) 11 for herbal plants and the green vegetables model (experiments were done with the grass barley), and Burken & Schnoors equation (4c) 12 for woody plants and the fruit tree model (experiments were done on poplars). The calculated TSCF (4a) is equivalent to the...

Metabolism And Genetic Engineering Studies For Herbicide Phytoremediation

SCHNOOR2 biochemistry and Cell Biology, Rice University, Houston, Texas, USA 2Civil and Environmental Engineering, University of Iowa, Iowa City, IA, 52242, USA - Fax 01 319 3355660 E-mail jerald-schnoor uiowa.edu Herbicides are extensively used for the purpose of crop cultivation and still remain as an important strategy for the commercial agriculture. However, the widespread use of herbicides has resulted in both point source and non-point source...

Molecular Ecological Methods

Molecular microbial ecology methods bypass culture-bias to provide direct measures of a variety of microbial community parameters. This section highlights some methods that are of particular value to bioremediation studies because of their ability to directly detect the presence, activity, diversity and abundance of degradative organisms. 4.2.1 DNA and RNA extraction methods Many molecular ecological analyses require bacterial DNA and or RNA to be extracted from soil. Depending on both the soil...

Molecular Engineering Advancements

Concurrently as the understanding of VOC phytoremediation have advanced, molecular engineering approaches to enhance processes are occurring and innovative applications to exploit specific plant systems have been designed. One line of molecular engineering has been to take advantage of the plant-microbe symbiosis. By selecting root-colonizing bacteria as recipients for enhanced degradation genes, the improved degradation of TCE has been observed in sealed reactors containing plants inoculated...

Phytoremediation

Phytoremediation or the use of vegetation at waste sites or contaminated soils can overcome limitations of microbial cleanup such as low bacterial population or inadequate microbial activity. Improving the quality of surface water and reducing nonpoint source pollution can be achieved using wetland vegetation or vegetative filter strips to reduce herbicide runoff. Plants can remediate environments contaminated with organic compounds directly via root uptake, detoxification by...

Planted Studies

Rhizoremediation experiments conducted by planting and monitoring microbial populations and or contaminant levels over time are powerful approaches since they can be constructed and operated with replication, randomisation and controlled conditions. Perhaps the major limitation of planted studies is time, since for reasons of practicality planted studies are typically only run for 1-3 years. Because roots are estimated to occupy less than 1 of soil 16 , it is reasonable to anticipate that many...

Processes Involved In Removal Of Pollutants

Why wetlands are so successful in removing a wide range of pollutants form wastewater becomes clear when the underlying processes are considered. Key to these processes is the heterogeneity of the substrate. The removal of nitrogen is a good example to illustrate this. Mineralisation of nitrogen from plant-derived organic compounds leads initially to the formation of ammonium. In the aerobic environment of the surface layer of the sediments and in the rhizosphere of plants, ammonium may be...

Removal Of Pollutants Via Plants

Phytoextraction refers to the removal of pollutants from soils or water through plant uptake 66 . In this approach, the pollutants are not simply recycled back into the wetland, as is the case in phytostabilisation, but they are removed from the system by harvesting the plants or by volatilisation through the plants. The latter only applies to substances that can form gaseous compounds, such as Se 22, 67 and Hg 28 . For phytoextraction through uptake and harvest to be effective, uptake by the...

Tnt

Plants lack the excretion system of animals. In plant cells toxic metabolites and pollutants are sequestered into the vacuole. This Phase III type process is an active one and is catalyzed by membrane-bound ATP-driven pumps. A recent study indicated the existence of a Phase III system in poplar 36 . 4. Detoxification of the active oxygen species generated by the pollutant in trees Activated oxygen species (hydrogen peroxide, superoxide anion, and hydroxyl radical) are produced at various...

Transformation Products

Detailed information on the chemistry of transformation products of inorganic and organic pollutants and metabolic pathways in susceptible and tolerant trees are scarcely available. In tolerant trees heavy-metal ions may be detoxified via chemical transformation into insoluble forms or chelated with cellular thiols or carboxylic acids and are eventually sequestered into the cell vacuole as described in herbaceous plants 8 . Of the different Phase II reactions that are most commonly involved in...

Uptake And Translocation Of Inorganic Pollutants

In soils metal ions are usually strongly bound to soil particles. To improve the bioavailability of metal micronutrients trees have evolved several strategies 6 , e.g. producing and secreting metal-chelating chemicals which, by chelation, mobilize iron, copper and zinc, as well as exuding protons in order to change the pH of the soil in the root zone, thereby solubilising the soil-bound metal ions 13 . The physiological and biochemical mechanisms that explain differences in metal mobility in...

Uptake And Translocation Of Organic Pollutants

Physicochemical and structural properties determine the uptake of organic chemicals by plant roots from the soil 16 . Aqueous solutions of moderately hydrophobic organic chemicals (characterized with an octanol-water partition coefficient log Kow of 1.03.5), such as low molecular weight aliphatics and aromatics, and chlorinated solvents dissolved in water are readily taken up by roots of trees and translocated to the aerial parts of the plant. Uptake of hydrophilic (log K< ,w< 1.0) and...

Preventing Establishment By Transgenic Mitigation

If a transgene confers even a small fitness disadvantage, the less fit transgenic volunteers and their own or hybrid progeny should only be able to exist as a very small proportion of the population. Therefore, it should be possible to mitigate volunteer establishment and gene flow by lowering the fitness of transgene recipients below the fitness of competitors, so that the volunteer or hybrid offspring will reproduce with considerably less success than its non-transgenic competitors. A concept...

Abc

Structure similarity between (A) Lignin monomer structure, where (1) X Y H (p-coumaryl alcohol), (2) X OMe Y H (coniferyl alcohol), (3) X Y OMe (sinapyl alcohol) 29 (B) 2,4-dichlorobiphenyl, PCB congener and (C) 2-4-dichlorophenoxyacetate. Among the first studies that specifically investigated the link between plant-derived chemicals and pollutant remediation was that by Donnelly et al., The authors demonstrated that a range of flavonoids could support the growth of PCB-degrading...

Days

Time course experiment of lindane disappearance in solution with chilli and coriander. Controls (white columns), chilli (black columns), coriander (grey columns). Data points represent the means of 5 replicates determinations. Bar SD. the effect of the rhizosphere on these compounds. Five plant species were harvested and separated into roots, stems and leaves Chenopodium vulgare, Solanum nigrum, Cytisus striatus, Vicia sativa and Avena sativa. Concentrations of total HCH in plant...

Oxygen Release By Roots Into Rhizosphere Of Helophytes

Oxygen reaching the root aerenchyma is respired by the root tissues and diffuses towards to the root apex and radially to the rhizosphere, to be consumed in the surrounding soil 54 . The oxygen flux from the root aerenchyma to the rhizosphere, known as radial oxygen loss (ROL), is determined by the concentration gradient, the consumption of oxygen by the cells along the radial path, and the physical resistance to oxygen diffusion 54, 56 . As a result, 30-40 of the oxygen supplied via the...

Rhizosphere Ecology

Yu et al., reported the recovery, by three to four orders of magnitude, of more resin acid degraders (tricyclic terpenoids originating from softwood trees) in hydrocarbon-contaminated soils than in pristine Arctic tundra soil 60 . Notably, the soil samples were collected thousands of kilometres from the nearest source of resin acids (conifer forest) and contained no native resin acids. The bacteria isolated in the study, Pseudomonas and Sphingomonas, are hydrocarbons degraders, which suggested...

Organic Compounds

It was shown that dissipation of condensed PAHs might be enhanced in the presence of AM fungi in the soil spiked with a mixture of different PAHs 127 . These results were consecutively verified in pot experiments conducted in two different industrially polluted soils 128 . In general, following explanations were suggested by the authors to elucidate the contribution of AM to PAH degradation i) mycorrhiza modifies root enzyme activity, exudation and architecture in a manner that stimulates PAH...

Sage

Serial analysis of gene expression (SAGE) is a method that allows the quantitative and simultaneous analysis of a large number of transcripts 42 . The first application of this technique in higher plants was used for profiling expressed genes in rice (Oryza sativa L.) seedlings 43 . Recent applications of SAGE technique in plants consist of wood formation in loblolly pine 44 gene expression pattern in the crop plant cassava (Manihot esculenta) from viral disease resistance and susceptible...