Short Excursion into the Biology of Arbuscular Mycorrhizal Fungi

More than 80 of all higher plants can undergo a symbiosis with arbuscular mycorrhizal fungi (AMF). Based on its activity, the arbuscular mycorrhiza is probably the most important symbiosis in nature. It appears to have developed at around the same time as the earliest land plants, in the Ordovician (Redecker et al. 2000). Scientifically, mycorrhizal all means by symbioses are not yet well understood due to the fact that the fungi cannot be grown independent of a host (Smith and Read 1997)....

Lid

Fig. 18.5 Shoot metal concentrations for the five planted treatments at harvest. Values shown are the means and standard errors of ten replicate pots (shoot material was pooled for each pot, dried, homogenized, and analyzed for metals). WT, wild-type Indian mustard APS, adenosine triphosphate sulfurylase overexpressing Indian mustard GS, glutathione synthetase overexpressing Indian mustard g-ECS, g-glutamylcysteine synthetase overexpressing Indian mustard. The letters above the bars indicate...

Mechanism of Phytoextraction

The metal contaminant must be mobilized into the soil solution for plants to be able to accumulate it. The bioavailability of a metal in soil can be increased in various ways (Fig. 19.6). In one mode of action, plants secrete phytosiderophores into the rhizosphere to chelate and solublize soil-bound metals (Kinnersely 1993). Acidification of the rhizosphere and exudation of carboxylates are considered potential methods of enhancing metal accumulation. In first instance, a metal mobilization has...

Soil Pollution

Mining, manufacturing, and the use of synthetic products (e.g., pesticides, paints, batteries, industrial waste, and applications of industrial or domestic sludge to the land) can result in heavy metal contamination of urban and agricultural soils. Heavy metals also occur naturally, but rarely at toxic levels. Potentially contaminated soils can occur at old landfill sites (particularly those that accepted industrial wastes), old orchards that used insecticides containing arsenic as an active...

Contributors

Ajit Varma Amity Institute of Microbial Technology, Amity University Uttar 310 Pradesh, Block 'E 3' Fourth Floor, Sector 125, Noida, Uttar Pradesh, India, 311 Andr Schmidt Institute for Microbiology, Friedrich-Schiller-University Jena, 313 Neugasse 25, 07743 Jena, Germany, smiddy74 yahoo.de 314 Andrea Zanuzzi Research Group Sustainable Use, Management and 315 Reclamation of Soil and Water, Agrarian Science and Technology Department, 316 Technical University of Cartagena, Paseo Alfonso XIII, 52,...

Extracellular Polymer Metal Interactions

Many bacteria produce large amounts of extracellular polysaccharides that have ionic properties and thus function as efficient biosorbents for metal cations. Interactions with metal ions are generally considered to be a direct consequence of the presence of negatively charged functional groups on these exopolymers. These groups include pyruvate, phosphate, hydroxyl, succinyl, and uronic acid. pH-dependent binding the positively charged cation to these groups can occur rapidly, with stability...

Nitrogen Mineralization Nitrification Denitrification and N2 Fixation

Nitrogen transformations in soils are very complex processes in which the nitrogen is simultaneously reduced and oxidized under different redox conditions by different microorganisms. The major processes involved in N cycling include ammonifi-cation, nitrification, denitrification, N2 fixation, dissimilatory reduction of nitrate to ammonium, and N immobilization. Ammonification, the process by which organic nitrogen is oxidized to create ammonia and ammonium, is a measure of N mineralization....

Chemical Processes Involved in the Bioremediation of Heavy Metal Contaminated Soils

Bioremediation involves the use of microorganisms to aid with the destruction of contaminants, a process called microbial metabolism. This process involves biochemical reactions or pathways that result in organism activity and growth, as well as the reproduction of the organism. The chemical processes involved in microbial metabolism make use of reactants, contaminants, oxygen, or other electron acceptors to convert metabolites to well-defined products. The microbial metabolism system enables...

Inhibition of Soil Enzymes

Metal Enzyme

An enzyme inhibitor is an agent that reduces enzyme activity, whereas an enzyme activator is an agent that stimulates enzyme activity (Voet and Voet 1995). The effects of inhibitors and activators on enzymes are shown in Fig. 11.1. Both of these types of agents affect the parameter Km for the enzyme reaction of interest (Km is the substrate concentration at which the reaction rate is half of the maximum rate Stryer 1995). As seen in Fig. 11.1, Km values increase in the presence of an inhibitor...

Effects of Earthworms on Heavy Metal Availability in the Soil

The heavy metal content of the soil is known to be mainly dependent on the structure of the soil's parent material and its physicochemical characteristics, and it can increase due to pollution resulting from agricultural practices and industrial activities. Although the total metal concentration (amount of metal that can be extracted with strong acid) is commonly evaluated in order to test for metal pollution of the soil, this may not reflect some important aspects, such as the mobility and...

Enzymatic Transformation of Metals

Microorganisms can carry out chemical transformations of heavy metals, such as oxidation and reduction, methylation and demethylation, and these are important to not only biogeochemical cycling but also many metal resistance mechanisms. Most research into metal transformation has concentrated on the involvement of bacteria in the mercury cycle, which can be represented as Mercury resistance is a common property of Gram-positive and Gram-negative bacteria, and the determinants are usually...

Ray Absorption Near Edge Structure

In the energy region near the absorption edge (K or L in subsequent discussions here), the slow photoelectron probes the empty electronic levels of the material. Therefore, the resulting pre-edge and edge structure within about 30 eV of the threshold (XANES) is rich in chemical and structural information. The theoretical picture that describes transitions from the inner shell (1s, 2s or 2p) to complex configurations of possible photoelectron final states (unoccupied valence bands in crystalline...

Extended XRay Absorption Fine Structure

EXAFS appears above the absorption edges whenever the absorbing atom is closely surrounded by other atoms, in other words in the solid state, in liquids, or in molecules in any aggregated state. It is only in the case of free atoms that there is no EXAFS component in the absorption spectrum, such as in noble gases or monatomic vapors (Rehr and Albers 2000 Kodre et al. 2002). EXAFS arises from the wavelike nature of the final photoelectron state. When an X-ray photon is absorbed, an inner-shell...

Zinc

Zinc is one of the most abundant metals in nature. The levels of Zn in plant materials are low and are generally in the range < 10-100 mg kg-1 of dry matter. Table 16.21 Effect of copper on the growth attributes of sugarcane (from Jain et al. 2008) Table 16.21 Effect of copper on the growth attributes of sugarcane (from Jain et al. 2008) Table 16.22 Effect of Cu on the root, shoot, and leaf weights of sugarcane (from Jain et al. 2008) Table 16.22 Effect of Cu on the root, shoot, and leaf...

Accumulation of Heavy Metals by Fungi

Elevated concentrations of toxic metals can occur in the fruitbodies of basidiomy-cetes in polluted environments, and soil saprotrophic and mycorrhizal fungi have been frequently proposed as suitable biomonitors of metal pollution (Kalac and Svoboda 2000 Collin-Hansen et al. 2002 Baldrian 2003). The extent of accumulation of individual metals is species or strain specific, with the high levels of metal enrichment in fungal fruitbodies serving as evidence of the high metal tolerance of fungi....

Substrates and Inhibitors

Laccases have low specificities for their reducing substrates but strong affinities for oxygen. Basically, any compound with characteristics similar to a diphenol will be oxidized by laccase as long as its redox potential is not too high (E < + 1,000 mV). Classical substrates of laccases include various lignin-derived phenols and aromatic amines. Orifto-substituted compounds (e.g., guaiacol, caffeic acid, gallic acid, dihydroxyphenylalanine, pyrogallol, o-phenylenediamine) tend to be better...

Standard Energy Dispersive XRay Fluorescence Analysis

The XRF analysis system consists of the excitation source and the X-ray spectrometer. In standard XRF, the elemental analysis is based on measurements of the XRF spectrum from the excited sample. XRF systems are classified according to the types of excitation sources and the types of detectors installed. The XRF mode in which the count rate and the energy (distribution) of characteristic X-rays are measured using an energy-dispersive X-ray spectrometer comprising the X-ray detector, electronic...

Bioremediation of Heavy Metals

Bioremediation can be defined as any process that uses microorganisms or their enzymes to return an environment altered by contaminants to its original condition. There are a number of advantages to bioremediation, which can be employed in areas that cannot be reached easily without excavation. It is well documented that the presence of metals in the soil impacts both the physiology and the ecology of microorganisms by inhibiting a broad range of microbial processes, including methane...

Indirect Methods

Several indirect methods are now available for measuring the soil microbial biomass. Among them, the chloroform fumigation method is the most commonly used approach. Microbial biomass C is now almost invariably measured by fumigation extraction (FE) (Vance et al. 1987) rather than fumigation incubation (FI) (Jenkinson and Powlson 1976). The FE method permits the measurement of microbial biomass when FI is invalid, such as in soils with pH values < 4.8. Significant reductions in microbial...

Microbial Function and Community Structure

An ecosystem has two major attributes, structure and function, which are intimately interconnected. This framework can be used to define and illustrate the damage that ecosystems can suffer for example after a heavy metal pollution event (Fig. 9.2). The original ecosystem may have high levels of both attributes (structure and function), but degradation might drive indicators of one or both attributes downwards (Bradshaw 2002). Thus, in terms of heavy metal polluted soils, degradations of both...

Specific Metallophytes and Their Potential Role in Phytoremediation

A botanist can immediately recognize that a site has a heavy metal soil due to the occurrence of metallophytes. In Central Europe, 3-6 plant species typically occur at every site polluted with heavy metals. However, for some unknown reason, no heavy metal soil contains every metallophyte. In many cases, metallophytes are relicts from the glacial period, only occurring in the plain at sites polluted with heavy metals, but thriving in alpine regions above the timberline or close to arctic areas...

Limitations of Phytoextraction

Phytoextraction and plant-assisted bioremediation are most effective when the soil contamination is limited to within three feet of the surface of soil, and when the groundwater table starts within ten feet of the surface (Raskin et al. 1994 Cunningham et al. 1997). It is applicable to sites with low-to-moderate soil contamination and to sites with large volumes of low-level contaminated groundwater that have to be cleaned (Salt et al. 1995). Scientists have investigated the effect of soil...

Analytical Methods for Bulk Samples 621 Basic Principles of XRay Fluorescence

Auger Effect Ray Principle

The process of XRF represents the basis for various analytical techniques. XRF is induced by the excitation (ionization) of atoms in the tightly bound inner K (for the elements 20 < Z < 50) and L (Z > 50) atomic shells with energies that must exceed the binding energies of the K and L electrons (Markowicz 1993). The atoms can be excited with X-rays, by irradiation from the X-ray tube or from a radioisotope source. Ionization of an inner atomic shell is achieved through the photoelectric...

Arbuscular Mycorrhizal Fungi in Heavy Metal Soils

Mycorrhizal Fungi Maize

Recent reviews on this subject are available thus (Leyval et al. 1997 Jeffries et al. 2003 Hildebrandt et al. 2007). The work of mainly C. Leyval and coworkers (Weissenhorn and Leyval 1993, 1995 Tonin et al. 2001) showed that polluted soils contain AMF fungi that are specifically adapted to soil pollution. It has often been stressed that specific AMF spores from heavy metal soils possess enormous potential for phytoremediation (Hildebrandt et al. 2007). However, most metallophytes at least most...

Microbial Diversity in Soils

Soil is a natural medium in which microbes live, multiply and die. Increasing attention is being directed towards microorganisms because the fertility of soil depends not only on its chemical composition but also on the qualitative and quantitative nature of the microorganisms inhabiting it. The maintenance of viable, diverse populations and functioning microbial communities in the soil is essential for sustainable agriculture (Beare et al. 1995 Benizri et al. 2002). Thus, interest in microbial...

Mobility of Heavy Metals in Tropical Land

Heavy metals exist in two forms in nature. As stated above, microbes can convert contaminants to less harmful products however, they can also immobilize contaminants (National Research Council 2003). Metal immobility is primarily achieved through reactions that cause the metal to precipitate or that keep the metal in a solid phase (Evanko Cynthia and Dzombak 1997). Chemical and physical properties affect the mobility of metals in soils and groundwater. Under acidic conditions (pH between 4.0...

Effects of Earthworms on the Soil

In general, the effects of earthworms on soil properties are related to their populations and activities, such as feeding, casting, and burrowing. The quality and quantity of their casts are important influences on soil characteristics. The main features of the soil that are influenced by earthworm activities are its physical (soil aggregation and infiltration), chemical (pH, organic matter, and available nutrient content), and biological (microbial populations and enzymatic activity)...

Functional Diversity and Community Level Physiological Profiles CLPPs

While molecular (genetic) or biochemical (phenotypic) diversity measurements have their place and generally measure the diversity of the numerically dominant members of the community (Loisel et al. 2006), functional diversity provides information on the functioning of the members of the soil microflora involved in the carbon cycle. Any loss in ability of the microbial community to maintain its wide range of functions is a warning sign of decreased soil health. Several approaches to measuring...

Role in Nature

Mammalian tyrosinases are located in specialized melanocytes and are responsible for the photoprotective pigmentation of hair, skin, and retina (Garc a-Borr n and Solano 2002). Disorders in tyrosinase-catalyzed melanin synthesis are not only an aesthetic problem they are linked with serious skin diseases, such as the well-known malignant melanoma. Vitiligo is another such disease, characterized by hypopigmentation and total melanocyte depletion in the basal layer of the epidermis. Immunological...

Factors Effecting Earthworm Distribution and Activity in the Soil

The distribution of earthworms in soil is largely controlled by climatic factors (i.e., rain and temperature) and the plant species and populations that are growing in the soil. Moreover, earthworm distributions and activities are also affected by soil physicochemical features (i.e., texture, pH, organic matter) and agricultural activities (tillage and fertilization, etc.). Earthworms are dominant members of the soil fauna Table 17.1 Ecological groups of relevant Central European earthworm...

Relation to Melanin

Melanins are a diverse group of polymeric pigments that are widespread in a variety of organisms ranging from bacteria to humans (Plonka and Grabacka 2006). Three main types can be distinguished (1) Eumelanins (black or brown) are produced during the course of the enzymatic oxidation of tyrosine to o-dihydroxyphenylalanine (DOPA) and dopaquinone (Fig. 13.2). The latter spontaneously converts via the unstable leucodopach-rome to red dopachrome, which can be used for the photometric determination...

Critical Limits for Heavy Metals in Soil

The heavy metal critical load depends on the acceptable total load from anthropogenic heavy metal inputs (deposition, fertilizers, other anthropogenic sources), below which ecosystem damage is unlikely. Methods for calculating critical loads for toxic metals are currently being developed within the United Nations Economic Commission for Europe (UNECE) Convention on Long-Range Transboundary Air Pollution (LRTAP) (De Vries and Bakker 1996 Slootweg et al. 2005). In the UK, a research consortium...

Detector

Fig. 6.3 Total reflection X-ray fluorescence (TXRF) geometry Fig. 6.3 Total reflection X-ray fluorescence (TXRF) geometry Fig. 6.4 Secondary target EDXRF geometry The following details can be identified Fig. 6.4 Secondary target EDXRF geometry detector (gas) can be used. However, one shortcoming of such a device is the poor energy resolution of the detector (800-1,000 eV at 5.9 keV), making the quantification of the insufficiently resolved characteristic X-ray lines in the measured spectrum...

Arbuscular Mycorrhizal Fungi and Salt Tolerance

About 7 of all land is polluted with sodium chloride or other salts and is thus not amenable to agriculture. The scale of this salt problem is thus considerably higher than that of heavy metal tolerance. The role of AMF in conferring salt tolerance to plants is ambiguous. Salt has repeatedly been reported to inhibit spore formation, hyphal growth, colonization of plants, and the formation of an effective symbiosis (Juniper and Abbott 1993, 2006). Many salt-resistant plants belong to the...

Utilization of Phytoremediation ByProducts

Phytoextraction involves growing plants in heavy metal contaminated soil until the metal concentration declines to tolerable levels. The metal removed can be determined by measuring the metal concentration in the plant, multiplying it by the biomass produced, and comparing this with the reduction in the metal concentration in the soil. In commercial phytoextraction, the next step is to dispose of the contaminated plant material. After harvesting, the plant is removed from the field, and this...

Other Halophytes

In some studies, terrestrial halophytes have been used to study tolerance to HMs and as putative candidates for phytoremediation. Such works are based on the idea (Ghnaya et al. 2005) that salt-tolerant (halophytic) plants would be better adapted to coping with environmental stresses, including HM than salt-sensitive (glycophytic) crop plants. To confirm such a possibility, the authors point to the rather high tolerance of two halophytes, Sesuvium portulacastrum and Mesembryanthemum...

Resilience of Microbial Function and Community Structure

In sustainable ecosystems, structure and function remain within a characteristic ranges over time, even in the face of natural disturbance. If a stress or disturbance does alter the ecosystem, it should be able to bounce back quickly. In this sense, soil resilience and resistance are important components of soil quality health, and key elements of sustainability theories (Seybold et al. 1999). Soil resilience has been defined as the capacity of a soil to recover its functional and structural...

Metal Factors

Enzyme activities are influenced in different ways by different metals due to the different chemical affinities of the enzymes in the soil system. Khan et al. (2007) found that Cd was more toxic to enzymes than Pb because of its greater mobility and lower affinity for soil colloids. Shen et al. (2005) found a negative interaction between Zn and Cd resulting from competition between them for sorption sites. Zn concentrations are generally higher (by factors of 100-1,000) than Cd concentrations...

References

Arcon I, Mirtic B, Kodre A (1998) Determination of valence states of chromium in calcium Chromates by using X-ray absorption near-edge structure (XANES) spectroscopy. J Am Ceram Soc 81 222-224 Arcon I, Kolar J, Kodre A, Hanzel D, Strlic M (2007) XANES analysis of Fe valence in iron gall inks. X-Ray Spectrom 36 199-205 Bhatia NP, Walsh KB, Orlic I, Siegele R, Ashwath N, Baker AJM (2004) Studies on spatial distribution of nickel in leaves and stems of the metal hyperaccumulator Stackhousia...

Treatment of Polluted Soils

Many agricultural and industrial activities produce numerous xenobiotics that affect both soil and aquatic environments. Recalcitrant xenobiotics can accumulate and become harmful to these environments and their inhabitants. Enzymatic treatment is considered an alternative method for the detoxification of contaminated aquatic and terrestrial environments (Sjoblad and Bollag 1981 Duran and Esposito 2000 Chiacchierini et al. 2004 Wesenberg et al. 2003 Claus and Filip 1991 Filip and Claus 1995...

Microbial Methylation of Heavy Metals 1431 Mercury

Mercury is one of the most widely distributed and best investigated metals that can be biomethylated. The inorganic form of Hg2+, but not Hg0, is a highly toxic metal ion that has the ability to interact with the sulfide bonds of enzymes and thus inhibit enzyme activity. The organic form is far more toxic because of its ability to cross lipid membranes and the blood-brain barrier, leading to interactions with the central nervous system. Therefore, the concentration of the organic form that is...

Oxidative Damage to Lipids

Lipid peroxidation proceeds via three phases activation, distribution and cleavage. The activation of one unsaturated fatty acid (linoleate) by one hydrogen radical results in the cleavage of one H+ atom from the methyl vinyl group of the fatty acid During this reaction, the resonance structure will react with triplet oxygen, which (as discussed above) is a biradical with two unpaired electrons. These unpaired electrons make it easy for triplet oxygen to react with other radicals. This reaction...

Induced Phytoextraction or Chelate Assisted Phytoextraction

Oligopeptide ligands, such as phytochelatins (PCs) and metallothioneins (MTs), are induced by the presence of or interact with heavy metals found in plant cells (Cobbett 2000). These peptides bind with the heavy metal, forming stable complexes, and thus neutralize them and minimize the toxicity of the metal ion 68 . Phytochelatins (PCs) are synthesized from glutathione, and have the structure Gly-(g-Glu-Cys)n, where n 2-11. Around a hundred phytochelating ligands have been reported in plant...

Genetic Aspects of Heavy Metal Resistance

With a few exceptions, genetic studies of metal-microbe interactions have been limited and often confined to studies of mutant strains, mainly because knowledge of the physiology and biochemistry of resistance is fragmentary in many cases. However, certain areas of metal-microbe interactions have received specific attention from genetics researchers, and this work has contributed not only to our knowledge of microbial responses to heavy metals but also to the wider fields of molecular biology...

Physicochemical Remediation

Incineration and soil washing are typical physicochemical soil remediation processes applied to munitions-contaminated soils. In the incineration treatment, the contaminated soil material is burned at 800-1000 C, but this is should be performed at a special plant that ensures that the exhaust fumes are detoxified. Hence, the process itself is very expensive, even ignoring the additional costs of excavation and transportation of the soil material, as incineration is an offsite process. This...

Lewis Acid Strength and Ionic Indices

Any positively charged ion is able to accept electrons, thus defining it as a Lewis acid. In contrast to the physical properties of a metal in its elemental form, the chemical properties of a metal ion determines its ability to form complexes (Pearson 1968), Table 2.1 Classification of some metals and metalloids according to covalent index (Nieboer and Class A elements Borderline elements Class B elements Li+, Na+, K+, Cs+, Be2+, Ga3+, In3+, Sn4+, Pb2+, As3+,Sb3+, Ti2+, T1+, Tl3+, Pb4+, Bi3+,...

Selenium and Arsenic

Selenium is, in contrast to mercury, a metalloid that is essential for the proper functioning of living organisms. It is involved in enzymatic and other biochemical reactions. Rotruck et al. (1973) showed that selenium has a protective function against oxidative stress. In proteins, selenium is a component of the twenty-first amino acid (selenocysteine), where it functions as a redox-sensitive centre. Another difference from mercury is that the methylation of selenium does not lead to a more...

Types of Microorganisms

Mycorrhizal Contamination

There are two different kinds of organisms that coexist in the contemporary living world the eukaryotes (more complex organisms with a true nucleus, which include algae, fungi, and protists), and the prokaryotes (simpler organisms without a defined nucleus). Prokaryotes include two microbial groups the eubacteria (including cyanobacteria blue-green algae) and the archaebacteria (a heterogeneous group with prokaryotic structure). If we consider the cell structure and function as criteria, there...

Ex Situ and In Situ Methods of Phytoremediation 19911 Ex Situ Methods

Here, the contaminated soil is treated on- or offsite, and then returned to its original site. Conventional ex situ methods applied to remediate polluted soils include excavation, detoxification, and or destruction of the contaminant physically or chemically, meaning that the contaminant undergoes stabilization, solidification, immobilization, incineration or destruction. These methods perform remediation without the need to excavate the contaminated site. Reed et al. defined in situ...

Metal Induced Responses in Plants

Soils with high concentrations of heavy metals can result from naturally high background levels or various anthropogenic activities. In plants, resistance to excess metals is achieved by avoidance (plants can restrict metal uptake) or tolerance (plants can cope with extreme internal metal concentrations). Thus, to survive in metal-polluted environments, plants have developed the two basic metal uptake and tolerance strategies of exclusion and accumulation (Baker 1981, 1987). In metal excluders,...

Intracellular Accumulation

The assimilation of metals by bacteria plays an important role in detoxification. Sigg (1987) presented a probable scenario for intracellular accumulation. Extracellular ligands or ligands attached to the cell wall are thought to bind toxic metals. These ligands transport the complexed metals through the cell wall in a slow transport step. The metals are released inside the cell, incorporated into biochemical pathways, or trapped in an inactive form via complexation with another high-affinity...

Swine Lagoon Effluents

The long-term use of swine lagoon effluents increased the extraction rates of plant-available heavy metals (Table 16.7). The mean absorptions of the heavy metals (Table 16.8) could be ordered as follows Zn> Cu Cr> Pb> Ni> Cd (Liu et al. 1996b). Table 16.7 Available (extracted in 0.1 M HCl) concentrations of heavy metals in the soil following long-term application of swine lagoon effluents (from Liu et al. 1996b) Soil Distance from Available content of heavy metal (mg kg 1 soil) Table...

Sources of Heavy Metal Contamination in Soil

Contamination of soils with heavy metals has mainly resulted from industrial activities, such as the mining and smelting of metalliferous ores, electroplating, gas exhausts, energy and fuel production, fertilizer and pesticide application, and the generation of municipal waste, fly ash, etc. As well as these anthropogenic activities, geogenic activities can also contaminate groundwater and soil with heavy metals such as arsenic and selenium. However, the human influence on heavy metals in soils...

Streptomyces Tyrosinases

Actinomycetes are Gram-positive soil bacteria with mycelial growth. Members of the genus Streptomyces are involved in the formation and or degradation of complex biopolymers like lignin, melanins, and humic substances (Kutzner 1968). In addition, they are important industrial sources of bioactive compounds such as antibiotics, antitumor agents, antiparasites, immunosuppressant agents, and enzymes (Anzai et al. 2008). About 40 of Streptomyces species produce melanin-like exopigments on...

In the Sugarcane Plant

Roots, stems and leaves of sugarcane (Saccharum spp.) were collected from 25 sites in an area under the direct influence of the municipal landfill site (MLS) and the medical waste treatment system (MWTS) of Ribeirao Preto, Sao Paulo, Brazil (Segura-Munoz 2006). The roots contained 0.22 0.12 mg Cd, 64.3 48.7 mg Cr, 140.6 27.7 mg Cu, 0.04 0.02 mg Hg, 561.6 283.3 mg Mn, 7.9 2.1 mg Pb, and 177.4 64.9 mg Zn kg-1 dry weight. Metal levels in stems were 80-90 of those found in roots, while the...

Phytoremediation

Phytoremediation is an emerging technology that exploits the genetic potential of selected plant species to remove, degrade, metabolize, or immobilize a wide range of contaminants. The concept of using plants to clean up contaminated environments is not new. About 300 years ago, plants were proposed for use in the treatment of wastewater (Hartman 1975). At the end of the nineteenth century, Thlaspi caerulescens and Viola calaminaria were the first plant species that were documented to...

Factors that Influence Metal Uptake

There are different pathways associated with the entry of dissolved substances into plant cells. The cytosol is a barrier between the vacuole and the outside of the plant cell that offers high resistance to the passage of any solution that includes salts and bases (Nultsch 2001). Plants have a natural tendency to take up metals, and their passage into plant cells will probably be hampered by this barrier. The effectiveness of the metal uptake is highly dependent on the availability, which in...

Effects of Heavy Metals on Fungal Physiology

Metals exert toxic effects in many ways they can 1 inhibit enzymes by the interactions with proteins 2 displace or substitute for essential metal ions 3 cause disruption of membranes, and 4 cause oxidative stress or interact with systems that normally protect against the harmful effects of free radicals. Growth reduction is a typical response of fungi to the toxicity of heavy metals Baldrian 2003 . It has been demonstrated that this reduction is dependent on nutrient availability, and that...

Genetic Engineering to Improve Phytoremediation

Plant productivity is controlled by many genes and is difficult to promote by single gene insertion. Genetic engineering techniques to implant more efficient accumulator genes into other plants have been suggested by many researchers Cunningham and Ow 1996 Brown et al. 1995 Chaney et al. 2000 . Implanting more efficient accumulator genes into other plants that are taller than natural plants increases the final biomass. Zhu et al. 1999 genetically engineered Brassica juncea to investigate...

Future Prospects for Phytoremediation

The acceptance of phytoextraction depends largely on its performance, the ultimate utilization of its by-products, and its overall economic viability. To date, commercial phytoextraction has been constrained by the expectation that site remediation should be achieved in a time comparable to other clean-up technologies. So far, most phytoremediation experiments have been performed at the lab scale, where plants grown in hydroponics setting are fed heavy metal diets. While these results are...