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Getting Started In Hydroponics

This e-book will take you on a journey, almost like going down a garden path, and help match the right system to your situation. Along the way you will discover the most powerful system, the easiest to build system, and the most forgiving system for maintenance. And the book will help you choose which system is right for you. You'll discover. The quickest, easiest hydroponics system to build. You can get started in hours rather than days and the system is built from common materials so you can save money. 5 ways you can get started in hydroponics on a pauper's budget. You don't have to get the most complex system to get incredible results. The e-book has 2 plans that can be built out of common materials you may already have. You can get the rest at Home Depot. Which crops to grow and which to stay away from. You can grow just about anything with hydroponics but some plants will take over, stealing light and space from smaller plants. This e-book will give you insights on which plants are the easiest. and tastiest. Forbidden Hideaway. The last chapter in the book shows you how to create a space in your home to grow plants that nobody will know about. To the outside world you are an ordinary neighbor. But inside the Grow Box a different world exists that makes plants grow like crazy. More here...

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The Use of Hydroponics and Plant Tissue Culture Technologies for Dye Degradation

The cultivation of plants and their further experiments with dye degradation can be carried out using hydroponic solutions. These solutions provide a nutrient status which is close to that of the soil in which the plant usually grows. Thus, such solutions are enriched with various macro and micro nutrients and can be used for the cultivation and or maintenance of plants for phytoremediation. The use of hydroponics provides a cost effective method for phytoremediation of dyes. Aubert and Schwitzguebel carried out the screening of plant species (Rheum rabarbarum, Rumex acetosa, Rumex hydrolapatum and Apium graveolens), in hydroponic solutions for the removal of sulfonated anthraquinones. Many plant species have the capacity to absorb large quantities of water form hydroponic solutions. The water absorption capacity of a plant is a factor that should be taken into consideration while performing studies in hydroponic solutions because it reflects the overall health of a plant. Lower water...

Opportunities in the Design and Creation of Transgenic

Although A. thaliana is a well characterized laboratory model plant, they are not suitable for phytoremediation applications, given its small stature and shallow root system. Poplar and aspen (Populus sp.), as well as willows (Salix sp.), on the contrary, are widely distributed, fast-growing, high biomass plants ideal for phytoremediation applications (Schnoor, 2000), thus, the development of transgenic trees is the main objective of many phytoremediation projects. As mentioned above, aspen (Populus seiboldii x Populus gradientata) transformed with a MnP from the fungus Trametes versicolor resulted in a more-rapid removal of bisphenol A from hydroponic media (Iimura et al., 2007). There are more examples related to other organic pollutants, as transformed poplar (Populus tremula x Populus alba) with rabbit CYP2E1 under the CaMV 35S promoter hairy root cultures exposed to TCE which resulted in the production of chloral and trichloroethanol higher than...

Amino Acids and Organic Acids

Ni-hyperaccumulator Alyssum montanum and a significant linear correlation in the xylem exudate concentrations of free His and Ni in several Ni-hyperaccumulators in the genus Alyssum. The addition of equimolar concentrations of exogenous L-His to a Ni-amended hydroponic rooting medium enhances Ni flux into the xylem in the non-accumulator A. montanum and Brassica juncea cv. vitasso. In B. juncea, reducing the entry of L-His into the root by supplying D-His instead of L-His or L-His in the presence of a 10-fold excess of L-alanine did not affect root Ni uptake, but reduced Ni release into the xylem., The root His concentrations are constitutively 4.4-fold higher in the hyperaccumulator A. lesbiacum as compared to B. juncea and did not increase within 9 h of exposure to Ni (Kerkeb and Kramer 2003). However, no increase has been observed in the concentration of free His in root, shoot, or xylem sap in Thlaspi goesingense in response to Ni exposure (Persans et al. 1999).

Stocks of Metals and Their Internal Heterogeneity

Magnetic ashes finding that magnetic fractions contained magnetite (Fe3O4), hematite (Fe2O3(III)), and some quartz (SiO2) and mullite (Al8 (O,OH,F)l(Si,Al)O4 4). The magnetic fractions had 10 times higher concentrations of Fe, and 2-4 times higher concentrations of Co, Ni, and Mn than nonmagnetic fly ashes (Kukier et al. 2003), and the concentrations in magnetic fly ashes were negatively correlated with elements associated with aluminosilicate matrix (Si, Al, K, Na). Jordanova et al. (2004) analyzed magnetic phases in the Danube River sediments and found a complex internal structure of the particles, including magnetite (Fe3O4) and to a lesser extent, oxides of other metals (including Cr, Ni, Zn, and Cu). Desenfant et al. (2004) demonstrated the association of magnetic anomalies with the distribution of lead, zinc, iron, and chromium in river sediments. The responsible particles were spherules of tenths of mm diameter and rich in iron oxides, in that cases derived probably from...

Methodologies for PMP Production

To produce foreign proteins in plants, it is necessary to first introduce appropriate coding DNA into the plant, and there are two different approaches to this i 67 . Either, plants can be stably transformed by means of Agrobacterium tumefaciens or by direct DNA uptake (biolistics, for example) so as to express the desired product. This method has the advantage that it is possible, by use of the appropriate promoter, to target expression to specific organs (leaves, roots, seeds), and once an appropriate transgenic plant has been produced, production can be scaled up in principle without limit yields of tobacco biomass can potentially exceed 100 tonnes ha 91 . Another option is to allow the recombinant protein to be released into the medium in hydroponic growth systems. However stably transformed plants may take time to generate and levels of expression in stably transformed

Plant Based Remediation of Selenium

Astragalus bisulcatus is a well-known Sehyperaccumulator that grows in soils containing high Se concentrations in southwestern United States . When these plants are grown hydroponically in the presence of selenate, while the older leaves contain mainly inorganic Se, Se in young leaves and shoots is up to 90 to 95 inorganic (Pickering et al ., 2003) . MetSeCys and SeCys represent 5 to 10 and 20 to 30 , respectively, of the total amino acid pool in the young shoots (Ellis and Salt, 2003) .

Development of irrigated Agriculture

After the large-scale construction of irrigation and drainage engineering, irrigated farmland area increases from 15.93 x 106 ha in 1950s to 48.89 106 ha in 1980s in China. After 1990s, the emphasis of farmland infrastructure construction has focused on the development of saving-water agriculture. Advanced irrigation techniques and reasonable irrigation scheme and irrigation norm according to crop species and growth stages are applied to increase water utilization. Open earthen irrigation channel is changed into pipe or anti-seepage disposed irrigation channel to decrease deep percolation of water. Drainage system is perfected, and considerable farmlands are leveled. All these measures improve water utilization efficiency on irrigated agriculture. Up to 2008, there are 447 irrigation regions with the irrigated area greater than 20 x 103 ha in China, and total area of effectively irrigated farmland is 58.47 x 106 ha. Of which, sprinkler and drip irrigation area accounts for 16.7 , the...

Herbicide resistance as a marker for gene flow

The herbicide difenzoquat is a mitosis inhibitor used for the post-emergence control of wild Avena spp. in winter cereals. Aegilops species are susceptible to this herbicide. Chinese Spring (CS) is a wheat cultivar possessing herbicide resistance alleles endowing resistance that can be used to obtain hybrid resistant progeny. The genetic control of tolerance to difenzoquat in bread wheat is determined by a major single gene (Busch et al., 1989). During our work we have conducted two types of assays which have enabled us to identify resistant hybrids growing plants with herbicides in hydroponic assays and herbicide spraying assays.

Mechanisms of the NaClHM Interaction

Similar correlations between salinity and Cd accumulation have been found for most plant species (although the opposite effect has also been obtained). This effect is usually explained by the salt-induced desorption of Cd that is tightly bound to the soil and its conversion into a bioavailable form. Therefore, this effect only manifests itself in plants growing in soil or on bottom sediment it disappears in experiments with soil-free solutions and with free-floating plants, like Elodea (as distinct from pondweed), where Cd penetrates through the leaf surface and predominantly into the intercellular space.

Plant Growth and Metal Distribution

Exposition of poplars to Cd affects their biomass production. A reduction in root and leaf dry mass was observed by Pietrini et al. (2010a) in clones from different poplar hybrids species (P. x generosa, P. x canadensis, P. deltoides, P. nigra, P. alba and P. trichocarpa) grown under Cd 50 M in hydroponics. Relative to control plants, some clones decreased their root and leaf dry mass by near 80 and 65 , respectively. However, some of them increased their root to leaf ratio, suggesting a higher tolerance to Cd stress. Negative effect on total biomass would be dependant on Cd concentration. Experiments with P. x canadensis cultured in pots containing distinct sort of soils with increasing Cd concentrations (0 - 1.5 mg kg-1) showed a negative tendency of total biomass production and Cd level (Wu et al., 2010). A reduction of plant growth has been also observed by Cu excess in poplars. Borghi et al. (2007) reported a general reduction of plant biomass and growth variables when plants of...

Action of Cu0 Nanoparticles on Plants

In more thorough investigations performed by Stampoulis et al. (2009) on Cucurbita pepo, the effects of Cu ENPs and bulk Cu powder were compared. Any effect on germination was not found. However, 15-day-long growth in hydro-ponic solution revealed the stronger inhibitory action of Cu ENPs on root length and biomass as compared with bulk Cu powder. Thus, root length was reduced by 77 in treatment with Cu ENPs, but only by 64 in treatment with bulk Cu powder. A decrease in biomass attained 90 in treatment with Cu ENPs, but only 69 in treatment with bulk Cu powder. An additional verification showed that a possible ionization of a small part of Cu during experiment did not change substantially a conclusion about the higher phytotoxicity of Cu ENPs as compared with that of bulk Cu powder.

Chemically Assisted HM Accumulation by Legume Microbe

There is evidence that legume plants are capable of actively accumulate HMs from polluted soils and hydroponics. For example, Cassia fistula accumulated Cr, Cu, Zn and Mn (Gupta and Sinha, 2007), Medicago sativa actively accumulated Cd, Cu, Ni and Zn (Peralta-Videa et al., 2002) and Cd, Cr and Ni (Bonfanceschi et al., 2009), and Prosopis juliflora accumulated Cd and Cu (Senthilkumar et al., 2005). However, comparison studies showed that legume species are characterised by relatively low translocation of HMs from roots to shoots and can be assigned to the excluder type (Kuboi et al., 1986 Pettersson, 1977 Zwarich and Mills, 1982). Metal hyperaccumulation trait was not found for plants of the family Fabaceae, and the exception is that Sesbania drummondii was described as Pb-hyperaccumulator having 40 mg Pb per g of dried shoot biomass (Sahi et al., 2002). Recently we have found that the root-shoot translocation factor of Pb for Lotus ornithopodioides was above 1, suggesting that this...

Water Resources Management

Virtually all of the studies on how to make much more efficient use of the limited resources in water shortage regions, including those in California85, show that the single most important inefficiency is in use of water for irrigation. Hence, a priority in both ICs and DCs is to develop practicable mechanics for resolving this problem. One approach is that used by Israel, where the severity of the problem has led to development of a new approach to agriculture called drip irrigation, in which the water is fed directly into the plant roots rather than into the soil around the plant. In due time, it is expected that many DCs will have to adapt to use of this approach.

Coalbed Methane Produced Water In The Western Us

SUBSURFACE DRIP IRRIGATION A relatively recent development for beneficial use and management of produced water from CBM production in the Powder River Basin is subsurface drip irrigation (SDI), sometimes also called horizontal injection. This system involves uniformly discharging produced water below ground, near the bottom of the root zone in agricultural fields, through a network of buried pipelines. The water is discharged to serve multiple purposes, including cropland irrigation, enhanced salt leaching from the soil profile, disposal of excess produced water, and shallow alluvial aquifer recharge.

Resistance or Tolerance to Metals in Plants

Tissue culture studies have demonstrated that multiple resistance to metals appeared in mature trees exposed to heavy metals in different contaminated areas (Watmough and Dickinson, 1996). Characteristics of resistance to metals can be induced in suspension cell cultures through successive exposures and gradual increases of the metal concentration in the growth media (Dickinson et al., 1992). Rooted cuttings of Salix sp. can be acclimated to metallic stresses in hydroponic conditions (Punshon and Dickinson, 1997).

Phytoremediation of Cyanide

Abstract Free cyanide and complex cyanide, including HCN and CN- is the most reactive and toxic substance of all industrial and anthropogenic pollutants. Many studies till date have proved that cyanide can be efficiently removed by plants. From the economic point of view, phytoremediation could be an attractive and useful technology in dealing with this dangerous pollutant. Phytoremediation of complex and free cyanide include removal of cyanide by terrestrial and aquatic plants. Experiments using free and complex cyanide have shown that many terrestrial and aquatic plants including willow, sorghum, cassava and water hyacinth can remove free cyanide from the hydroponic media. Cyanide uptake in plants can be associated with very complex physiological mechanisms which include transport and assimilation of cyanide within the plants for catering plant's nitrogen needs. Transport and metabolism of different chemical species of cyanide differ in various plant species including trees, grasses...

Studies on Copper Tolerance and Uptake

Metal tolerance in plants may be estimated using various approaches. One common stress test involves measuring photosynthetic activity, because especially photosystem II is very sensitive to metals, in particular to copper. Using portable chlorophyll fluorimeters, photosynthetic yield can be measured (e.g., Mallick and Mohn 2003). Another method is the root elongation test (Wilkins 1957), where an index of metal tolerance is derived from plants growing in hydroponics. The rate of root growth is measured in the control medium and again after the addition of different concentrations of the metals.

Examples of the Application of IR Microspectroscopy

Synchrotron Fourier Transform IR Microspec-troscopy A New Tool for Monitoring the Fate of Organic Contaminants in Plants. Phytoremediation is a process wherein plants absorb and biodegrade antheopogenic pollutants from contaminated soil. Dokken et al. (2005a) explored the use of IR spectromicroscopy to examine the fate of contaminant directly in plant material. The authors used FTIR spectromicroscopy to monitor the fate and effects of 2,6-dinotrotoluene (2,6-DNT) in corn (Zea mays) roots. Seedlings were grown hydroponically and exposed to 0, 5, 10, and 15mg L of 2,6-dinotrotoluene. Root material was frozen in Tissue-Tek OCT (Sakura Finetek USA, Inc., Torrance, CA) at 40 C, and 4-mm sections were prepared and mounted on IR reflecting low-E glass microscope slides. The IR imaging indicated that 2, 6-DNT may be incorporated in the lignin in corn plants. The detection of the nitro peak at 1530 cm 1, CH3 peaks, and bands typical of aromatic ring structures are indicative of a...

Bioassays in selectivity and resistance to herbicides

Conventional breeding programs frequently don't consider the herbicide response of cultivars during the selection process, it is why some cultivars show problems when treated with herbicides in culture in field. This is particularly true for crop response to new herbicides or new use of an herbicide. Cultivars show wide differences in response to herbicides and in many cases the concentration of herbicide needed to control weeds, or a particular weed, is deleterious if not lethal to the crop. For example, the control of Bromus diandrus in cereals is of concern. Bromes are vigorous competitors in winter cereals in many parts of the world (Blacksshaw, 1993) and cultural methods are the basis for their control because the herbicides used for weed control in cereals are not effective in controlling brome grass. The development of a sulfonilurea herbicide allowed a good control of Bromus spp in wheat. Hydroponic in vitro herbicide treatments were carried out. In those assays, germinated...

Impact of Cu on the Structure of Elsholtzia splendens

Elsholtzia splendens grows vastly over copper-mined areas and was first recognized for its value in the exploration of copper ores in the 1950s (Hsieh and Hsu 1954). It has a local nickname copper flower because of its growth confined in highly Cu-contaminated soils. Through old mined area survey, pot experiment, and hydro-ponic culture, the ability of Cu accumulation by Elsholtzia splendens and its influencing factors was discussed in this section. 17.4.1.3 Cu Concentration of Elsholtzia splendens in Hydroponic Conditions

Factors Influencing Cu Uptake and Accumulation by Elsholtzia splendens

PH when free Cu2+ activity was held constant, suggesting a higher phytoavailability of free Cu2+ at a higher pH. The positive effect of increasing pH may be explained by the increased binding capacity of a biotic surface (e.g., root cell walls and membranes) at a higher pH. Similar observations that Cu binding to the cell walls of maize roots increased with pH and that Cu toxicity to plants often increases with increasing pH in hydroponic culture experiments were also found (Plette et al. 1996). In addition, exudation of organic acids by plant roots, such as citric acid, is of great significance due to their metal chelating complexing properties for the mobilization of heavy metals (Mench et al. 1988). It was suggested that application of citric acid (3.6 g C kg1) significantly increased the extractable Cu concentration in planted and implanted soils and facilitated Cu uptake by Elsholtzia splendens (Chen et al. 2006). However, Jiang et al. (2004) found that citric acid had no marked...

Technologies and Costs for Coalbed Methane Produced Water Treatment

Numerous treatment technologies may be used for coalbed methane (CBM) produced water to achieve water qualities suitable for beneficial uses or to comply with permitted discharge requirements. The vast majority of CBM produced water treatment is completed for the purpose of disposal (see Chapters 4 and 5). Treatment is therefore generally performed either as a regulatory requirement of the Underground Injection Control (UIC) program to facilitate subsurface drip irrigation or for National Pollutant Discharge Elimination System (NPDES)-issued permits for discharge to ephemeral and perennial drainages (see Chapter 3). If the water is treated prior to deep reinjection disposal the treatment is done for operational purposes or to address bacterial contamination (see Chapter 4).

Future Perspectives

Decomposition methods of keratinic waste like incineration or chemical treatments (Onifade et al. 1998) are rather expensive or environment-polluting. In contrast, Present day biotechnology offered an environmentally sound two stage fermentation system for conversion of keratinic waste into a useful product, biohydrogen (Balint et al. 2005). A keratin-degrading Bacillus strain (Perei et al. 2000) was used to obtain fermentation product which was rich in amino acids and peptides and subsequently used as major nutrient source for an anaerobic hyperthermophilic archaeon, Thermococcus litoralis, which produced hydrogen gas as a physiological byproduct. Besides T. litoralis, E. coli and Caldicellusiruptor saccharolyticus capable of producing hydrogen were also examined but neither of them could utilize the keratin hydrolysate for biohydrogen production (Balint 2006) . The application of keratinase as a detergent additive has also been suggested (Gupta and Ramnani 2006). Another field of...

Theoretical Framework for Coupling Environmental Entities in Order to Characterize Scale Specific Processes in

Fig. 19.2 General representation of a pseudohierarchy of environmental entities (Env) showing the coupling mechanism with external entities (acronym Ex, continuous arrows) at each scale, which generate scale-specific patterns, and implicitly the partial decoupling (dashed arrows) of the larger scale patterns from smaller scale mechanisms and associated patterns. The environmental systems Env1 from scales 1 to 3 (e.g., soils, biological systems, hydro-systems, ecosystems, socioeconomic systems) are not a true hierarchy of nested systems, as usually approached in a systems analyses context, but only a pseudohierarchy including in their structure new entities at each scale (usually conceptualized as external driving forces, or forcing functions in a nested hierarchy paradigm). In order to observe the complex environmental entity Env-Ex, one needs a scope of observation larger than the scope associated with the scale of Env or of Ex taken separately

Scale Specific Processes in Metal Biogeochemistry

Fig. 19.3 General representation of the structure of a model in an integrated approach in order to assess the effects of local processes involving metals at one space-time location on other local processes at large distance in space-time (designate by '). Env1_1 can be a tailing-dam or a mining dump or a polluted soil, or a complex soil-vegetation entity. Env2 (scale 1-3) can be hydrosystems, Ex2 can be geomorphological, pedologic and microclimatic entities in the landscape, Ex3 geologic and regional climatic features of a larger catchment, and the model could attempt to predict the effects of local phyto-remediation of a contaminated site in the slope area of a small catchment on late and distant bioaccumulation of metals in crops in an agricultural floodplain site. The coupling at the same scale and between scales is based on variables characterizing the coupled entities. Successive up-scaling and downscaling of some variables are needed in order to predict ST large-distance effects...

Rhizoremediation with Poplars

In addition, they can uptake, hydrolyze, and dealkylate atrazine to less toxic metabolites (Burken and Schnoor 1996, 1997). It has also been shown that they can take up and transpire dioxane in both hydroponic and soil experiments (Aitchison et al., 2000). Further, they can take up and translocate from root to shoots lesser-chlorinated polychlorinated biphenyls (PCBs), being the translocation of PCBs to stems inversely related to PCB hydrophobicity (Liu and Schnoor, 2008). Moreover, in vivo metabolism of 3,3',4,4'-tetrachlorobiphenyl through hidroxilation was observed (Liu et al., 2009). It is noteworthy to report that poplars are among the few tree genera that can associate in a mutualistic symbiosis with both types of mycorrhizal fungi (ectomycorrhizae and vesicular arbuscular mycorrhizae), which have a fundamental role in increasing the root surface up to 800 fold. However, it is not clear if the fungi can directly degrade the contaminant or if they stimulate...

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 promising, scientists readily admit that solution culture is quite different from that of soil. In real soil, many metals are tied up in insoluble forms, making them less available, which is the biggest hurdle to extracting them from the soil (Kochian 1996). Phytoremediation is still in its research and development phase, and there are many technical barriers to this approach that need to be addressed. Both agronomic management practices and plant genetic abilities need to be optimized to develop...

Transgenic Plants for Remediation of Phenolic Compounds

Basically, transgenic technology has focused in two principal strategies to improve pollutants removal (1) the manipulation of phase I of metabolic activity to enlarge in planta degradation rates, or to impart novel metabolic activity, and (2) the enhanced secretion of reactive enzymes from roots leading to accelerate ex planta degradation of organic contaminants (James and Strand, 2009). Although many investigations that have pursued the increase of in planta degradation rates could be assayed in phenol phytoremediation, the principal strategy applied with this class of contaminant has been the ex planta degradation. Probably, to avoid the potential accumulation of toxic metabolites due to the incomplete phenol metabolizing that occurs in plants. In the first case, since cytochrome P450-mediated oxidation reactions are the most important in phase I of in planta transformations, overexpression of many P450 proteins have been largely applied to enhance phytoremediation of organic...

Versatile Application Methods for Neonicotinoids

For example, imidacloprid (Confidor) can be applied with a drop nozzle'' (a bell shaped spraying gun) so that the product drops on the leaves with a regulated droplet size (avoidance of spray drifting), pours down the stem and the remaining portion gets down to the soil. By this method initial efficacy is achieved on the leaves and long lasting efficacy provided by uptake via the stem and root system. Soil applications, e.g. by drip irrigation, are safe for a wider range of beneficial insects such as Pseudaphycus flavidulus, Leucopis sp. and Sympherobius maculipennis Kimmins which are predators of mealybugs and mites. Drip irrigation The in-furrow application of imidacloprid (Admire) and thiamethoxam (Actara) is commonly used in potato and vegetable crops. To ensure root uptake, the neonicotinoid is applied at specified doses as in-furrow spray during planting or as a narrow band directly below the seed row some days before planting in a bedding operation. The float system technology...

Phytoremediation of Heavy Metal Polluted Soil

Rhizofiltration is primarily used to remediate extracted groundwater, surface water, and wastewater with low contaminant concentrations (Ensley 2000). It is defined as the use of plants, both terrestrial and aquatic, to absorb, concentrate, and precipitate contaminants from polluted aqueous sources in their roots. Rhizofiltration can be used for Pb, Cd, Cu, Ni, Zn, and Cr, which are primarily retained within the roots (United States Protection Agency 2000 Jing et al. 2007). The advantages associated with rhizofiltration are the ability to use both terrestrial and aquatic plants for either in situ or ex situ applications. Another advantage is that contaminants do not have to be translocated to the shoots. Thus, species other than hyperaccumulators may be used. Terrestrial plants are preferred because they have a fibrous and much longer root system, increasing the amount of root area (Raskin and Ensley 2000). Dushenkov et al. (1995) observed that roots of many hydroponically grown...

Safronova G Piluzza S Bullitta and A A Belimov

There is evidence that many legume species of the flowering plant family Fabaceae may be efficiently used in phytoremediation of heavy metal polluted soils, particularly for revegetation and phytostabilization of mine soils. For such purposes, a number of legume species were used and this chapter gives an updated glimpse on scientific experiences dealing with microbial effects on several legume species growing in heavy metal polluted soils. Legume species are able to form symbiosis with various beneficial microorganisms, such as nitrogen-fixing nodule bacteria, arbuscular mycorrhizal fungi and plant growth-promoting bacteria. Such plant microbe associations have implications in plant growth, nutrition and disease control. The symbioses between legumes and microorganisms provide nutrients for the plant, stimulate plant growth, exert antistress effects on plants, improve soil fertility, and restore ecosystem biodiversity and functions. This makes legumes very tempting subjects for...

Flyash Induced Oxidative Stress And Tolerance In Prosopis Juliflora Grown

Belimov, AA Safronova, V Demchinskayaa, SV Dzyuba, OO. Intraspecific variability of cadmium tolerance in hydroponically grown Indian mustard (Brassica juncea (L.) Czern.) seedlings. Acta Physio.lPlant, 2007, 29, 473-478. Bonfanceschi, BA Flocco, CG Donati, ER. Study of the heavy metal phytoextraction capacity of two forage species growing in an hydroponic environment. J. Hazard Mater, 2009, 165, 366-371.

Phytoremediation of Toxins

The primary solution for the remediation of soils affected with explosive chemicals is soil evacuation and ex-situ treatment by incineration or secured land-filling. However, this method is extremely cost-intensive, destructive to the environment, and not practicable by any means. In this situation, bioremediation is an affordable and environment-friendly method and has been evaluated using a number of bacterial strains and a few plant species. A number of fungi, yeast, bacteria and other microorganisms present in the root zone (rhizosphere) of higher plants have been shown to break down organics such as explosives, fuels and solvents (French et al. 1998 Bhadra et al. 1999 Burken et al. 2000 Hawari et al. 2000). Among plants, willow and poplar have been extensively used in the cleaning-up of soils contaminated with toxic explosives. It has been reported that hybrid poplar (Populus deltoids x P. nigra) is very effective in removal of TNT when it was grown in hydroponic solution, but it...

Movement in Plant Tissues

The spinosyns have demonstrated significant translaminar and systemic mobility in plants. Spinosad and spinetoram control larvae of Liriomyza spp. and the early larval instars of some lepidopterous larvae by moving through the upper epidermis into the mesophyll tissue within treated leaves.111,112 Spinosad movement through the leaf epidermis can be increased with the addition of penetrating surfactants to the spray mixture.112 Once in the mesophyll, spinosyn residues do not appear to move out of treated leaves. The spinosyns can also be taken up by plant roots and move acropetally in vascular tissue. When administered to the roots of hydroponically-grown plants, spinosad can control Spo-doptera littoralis (Egyptian cotton leafworm) larvae, Trialeurodes vaporariorum (greenhouse whitefly) nymphs and Tetranychus urticae (twospotted spider mite) motile stages.113,114 Spinosad applied as a soil drench has significantly reduced emergence of adult Liriomyza huidobrensis (pea leafminer) from...

Phytoremediation with Genetically Modified Legumes and Symbiotrophic Microorganisms

Welch and LaRue (1990) isolated Pisum sativum mutant named E107 (brz), with an abnormally high uptake of Fe and characteristic necrotic spots on leaves due to Fe toxicity. The roots of the E107 released Fe(III)-reducing substances to the surrounding medium at higher rates than the wild type Sparkle, suggesting that the mutant acts functionally as a Fe-deficient plant. This mutant excessively accumulated Al and manifested symptoms typical of Al toxicity (Guinel and LaRue, 1993). More recently it was shown that in soil culture the mutant E107 actively accumulated other metal ions including Ca, Cu, Mg, Mn, Zn, and particularly Pb, which is usually present in soil as insoluble component (Chen and Huang, 2007). When the soil was supplemented with EDTA, the genotypic differences between the E107 and wild type plants were not manifested, suggesting that metal availability in the root zone was a crucial factor mediating excessive metal accumulation. Another mutant was obtained on Medicago...

Mechanisms of Silver Nanoparticle Formation

One of the driving forces for the uptake of silver metal ions is the concentration gradient between the silver ions in the soil solution and the silver ions in the plant fluid. A high concentration in the soil water (or hydroponic solution) will increase this driving force. A low concentration in the plant will also increase this driving force. The concentration in the soil water may sometimes be increased by using an agent to enhance the solubility the metal, and for this reason complexing agents are used in phytoremediation for various partially soluble metals. Generally this is not an issue with hydroponic plant growth.

Common Reclamation Methods and Reclamation Efficiency

Furrow leaching or alternate row (or border) leaching belongs to partial leaching, and its purpose is to maintain a suitable salinity level in crop beds or planting area by transporting soil salts laterally into the unirrigated area. This method is suitable to high groundwater table. Similar to furrow leaching, drip irrigation leaching also can remove salt away from the infiltrating areas. However, under drip leaching, salt will accumulate seriously on the lateral edges of the wetted area, in crop bed ridges, or at the soil surface between emitters (Keren, 2000 Burt and Isbell, 2005). Drip irrigation leaching is helpful to the establishment of a new plant in highly salt-affected soil (Burt and Isbell, 2005). Partial leaching methods can maintain reasonable soil aeration and planting during soil reclamation. However, additional methods to remove or alleviate salinity level in the root zone of planting area such as rainfall leaching or local ponding leaching usually are required under...

Phytoremediation A Potential Tool of Bioremediation

Roots of hydroponically grown Solar-powered hydroponic Technique, small scale clean-up. Hydroponic technique, industrial Hydroponic technique, contaminated water The process involves raising plants hydroponically and transplanting them into metal-polluted waters where plants absorb and concentrate the metals in their roots and shoots 4, 108-110 . Plant roots can solubilize heavy metals by acidifying their soil environment with protons extruded from the roots. A lower pH releases soil bounded metal ions into the soil solution. Solubilized metal ions may enter the root either via the extracellular or intracellular pathways. As they become saturated with the metal contaminants, roots or whole plants are harvested for disposal 109, 110 . Dushenkov et al. 108 elucidated that the translocation of metals to shoots would decrease the efficiency of rhizofiltration by increasing the amount of contaminated plant residue required for disposal. However, Zhu et al. 110 suggest that the efficiency...

Uptake of Phenol and its Derivatives

Plants play a direct role in the removal of a contaminant by (1) sorption on plant tissues and or (2) uptake and subsequent translocation, metabolization, storage or volatilization. Sorption to roots would be considered the first step, because when pollutants present in soil water or groundwater come into contact with roots, they may sorb or bind to the root structure and cell walls. Such sorption should be relatively reversible or not, depending on different variables. The sorption of contaminants to the root surface has been reported in several plant species and it can be estimated in control experiments using dead or inactivated biomass. For instance, phenolic compounds are partially adsorbed onto roots and this process of nonspecific binding by physical sorption to plant tissues contributed for phenol removal from the liquid medium (Dec and Bollag, 1994 Santos de Araujo et al., 2006 Coniglio et al., 2008 Sosa Alderete et al., 2009). However, the use of appropriate controls, have...

Arabidopsis arenosa L Lawalre 12411 Biology and Ecology

The root systems of metallophytes have been little studied outside hydroponic cultures although the root system morphology, particularly its length is important in solute uptake (Fitter 2002) and thus in phytoextraction efficiency. On agar media with increased concentration of Cr(VI) (Castro et al. 2007) or Cu(II) (Lequeux et al. 2010 Pasternak et al. 2005) reorganization of root system architecture resulted The concentration of Cd and Cu accumulated in R. acetosella leaves never exceeded that in the soils of both sites as documented by BCF < 1 (Table 12.3). Our results confirmed also the capability of R. acetosella to take up Cd in concentrations higher than those in the majority of plant species (12.9 mg kg-1 in population A). The TF > 1 for Cd was recorded in both sites (Table 12.3). R. acetosella accumulated higher amount of Cu in the roots than in the leaves (Fig. 12.2) in both localities (maximum 88 mg kg-1), similarly as R. acetosella plants grown in hydroponic culture...

Persistent Organic Pollutants

Investigations seeking to characterize the ex-planta and in planta mechanisms by which C. pepo ssp. pepo extracts weathered POPs from soil and translocates the contaminants within the vascular cylinder, respectively, are ongoing. Under either soil-based or hydroponic conditions, C. pepo ssp. pepo exudes larger amounts of low-molecular-weight organic acids than do other cucurbits. This enhanced exudation of organic acids is likely an evolved nutrient acquisition strategy, but importantly, this increased root exudation correlates with greater POP extraction from soil (Gent et al. 2005). The mechanism of in planta POP translocation remains unknown, although preliminary data with grafted cucurbits suggest a unique transport system within C. pepo ssp. pepo root tissue (Mattina et al. 2006).

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 species exposed to heavy metals (Rauser 1999). MTs are small, gene-encoded, Cys-rich polypeptides. PCs are functionally the same as MTs (Grill et al. 1987). Chelating agents such as ethylenediaminetetraacetic acid (EDTA) have been isolated from plants that are involved in the uptake of heavy metals and their detoxification. The addition of chelators to a Pb-contaminated soil (total soil Pb 2,500 mg kg-1) increased shoot Pb concentrations of Zea mays (corn) and Pisun sativum (pea) from less than 500...

Oxygen Release By Roots Into Rhizosphere Of Helophytes

Different methods to estimate oxygen flow rates have been used, mainly in plant-physiological investigations 50 . Rates of 126 mol O2 h g root dry mass for Juncus ingens (giant rush) and 120-200 mol O2 h g root dry mass for Typha latifolia (cattail) determined by the titanium-citrate method are of technological relevance 85, 86 . Furthermore, model calculations for Phragmites australis (reed) resulting in oxygen input rates of 5-12 g O2 m2 patch area per day 86 and investigations with individual plantlets of different species in hydroponic cultures resulting in the highest oxygen release rates of 1.4 mg O2 h plantlet for T. latifolia 84 highlight from a more biotechnological view the considerable potential of helophytes to release oxygen. Some studies have revealed that the redox state of the rhizosphere has a significant effect on the intensity of oxygen release of various helophytes, with oxygen release rates increasing as the soil Eh becomes more reduced 85, 87, 88, 84 . In...

Phytoremediation Case Studies

Several experiments, mostly hydroponic experiments have been conducted for phytoremediation of cyanide. Investigation on the potential of Chinese vegetation to degrade cyanide revealed that detached leaves (1.5 g fresh weight) from 28 species of Chinese vegetation plants in aqueous solution spiked with potassium cyanide can remove cyanide from the solution in variable amounts (Table 18.2) (Yu et al. 2004). Cyanide concentrations ranged from 0.83 to 1.0 CN mg L-1. The fastest cyanide removal reported is for Chinese elder, Sambucus chinensis, with a removal capacity of 8.8 mg CN kg-1 h-1, followed by upright hedge-parsley (Torilis japonica) with a value of 7.5 mg CN kg-1 h-1. The lowest removal capacity of cyanide has been noted for snow-pine tree (Credrus deodara (Roxb.) Loud). Results from various studies have indicated that a wide range of plant species can efficiently metabolize cyanide. It is therefore, cyanide elimination with plants is a feasible option for cleaning soils and...

Phytoremediation Detoxification of Explosives by Plants

The two greatest advantages of phytoremediation compared with traditional abatement methods are (1) cost effectiveness, and (2) soils remain in place thereby causing less ecosystem disruption. Cropping systems with costs ranging between US 200 and US 10,000 ha-1 would correspond to a remediation cost of US 0.021.00 m-3 of soil per year, which is a saving of many orders of magnitude when compared to costs associated with physicochemical remediation technologies (Cunningham et al. 1995). There are several studies which show that plants, in general, readily take up RDX and TNT. For example, recently Vila and others reported that agronomic plants (maize, soybean, wheat, and rice) could grow on soils containing RDX and TNT and were able to uptake these compounds (Vila et al. 2007). In another recent study, it was reported that maize (Zea mays L.) and broad beans (Vicia faba L.) were able to remove TNT from soils (Van Dillewijn et al. 2007). Also, Catharanthus roseus (Vinca) hairy root...

Natural Hyperaccumulators

Several plant genera, as well as some microbes and fungi, are natural hyperaccumulators of heavy metals. It is suspected that their enhanced abilities to accumulate, translocate, and detoxify and sequester heavy metal ions evolved in some taxa to protect against disease and insect herbivores, similar to the function of glucosinolates (Salt 2006). The Brassicaceae family contains the largest number of hyperaccumulators with 11 genera (Prasad and Freitas 2003). Thlaspi species can accumulate cadmium, nickel, lead, and zinc. Cysteine and other low molecular weight thiols have been implicated in the ability of Thlaspi caerulescens to hyperaccumulate cadmium (Hernandez-Allica et al. 2006). B. juncea (Indian mustard) is known for its ability to accumulate cadmium, chromium, copper, nickel, lead, and zinc. Several aquatic species, such as duckweed (Lemma minor) and water hyacinth (Eichhornia crassipes) take up metal ions from contaminated water. Sunflower has been shown to remove lead,...

Theoretical Considerations

Consider first the simpler case of a partition-limited model for the plant uptake of nonionic contaminants from a soil-free nutrient solution by passive transport through the plant vascular system. Here water is both the solvent for the contaminant and the medium that carries it to plant roots (and to other water-contacted surfaces) and eventually to other parts of the plant via the plant vascular system. The overall plant uptake process is driven by the external-water concentration and is considered to consist of a series of partition uptakes, with the understanding that the contaminant concentrations within the plant may or may not come to full equilibrium with the external water solution. On the other hand, for any given volume element inside the plant, local equilibrium is assumed for a contaminant between sap water and the various organic constituents within that volume element. With these considerations, the concentration of a contaminant either in the whole plant or in a...

Conclusion

Some transgenic plants and, also microorganisms will be necessary to achieve this goal. Secondly, genetic engineering could be useful to produce hybrid or the novo enzymes to transform or even mineralize complex compounds, which are difficult to metabolize. In this chapter, we have presented some examples in which successful results were obtained using the above mentioned technology. However, it is expected that considering the recent advances in genetics, proteomics and metabolomics, novel genes expressing detoxifying enzymes could be cloned and expressed into plants allowing the host plant to have a wider range of phytoremediation capabilities. These plant improvements may have great potential for field applications assuming public acceptance of the use of more genetically modified organisms. Emphasis should be put on evaluating results obtained in simplified experiments, such as those performed with in vitro cultures, hydroponics or pot plants, and on applying these findings to...

Hydropower

Only small, mini and micro-hydro systems, which do not have impacts on the environment, are sustainable and manageable by the local community (Pokharel et al. 2006). WEC (2001) reported the survey result that the world hydropower potential is approximately 2360 GW of which approximately 700 GW has already been exploited. The development of half of the total hydro potential could lead to the reduction of approximately 13 of greenhouse gas emissions due to avoiding the use of fossil fuels as reported by WEC in 2001. Careful planning and development of hydropower projects is crucial in order to have the minimum social and environmental impact in the project areas. Hydropower, especially small, mini, and micro-hydro power development, is a key to addressing the global environmental problems due to energy generation.

Crop Plants

Muehling and Lauchli (2003) studied two wheat genotypes (T. aestivum and a salt-tolerant amphiploid, T. aestivum x Agropyron elongatum Host.) the plants were grown hydroponically. NaCl (75 mM) stress and Cd (10 M) stress led to significant decreases in shoot yield in both wheat genotypes however, combined treatment with the two stresses did not lead to further decreases in shoot and root Smykalova and Zamecnikova (2003) showed that biomass accumulation in barley plants grown hydroponically for seven days was equally suppressed in the presence of 10 M Cd and 100 mM NaCl (down to 76.7 and 74.4 , respectively) the combined action of these factors only slightly enhanced the negative effect (suppressed to 61.6 ). A similar inhibitory effect on Cd accumulation in the roots (61.0 of the accumulation of the control) was exerted by a combined treatment a slightly lower effect was observed on shoots (69.3 of the accumulation of the control). This indicated that Cd translocation to shoots was...

Field studies

Field studies conducted to evaluate herbicide dissipation of herbicides had two distinct research objectives. However, all experiments were conducted similarly. Bed formation (20 cm raised bed), single drip irrigation tube, and lying of 32 um-thick (1.25 mil) low density polyethylene mulchoccurred simultaneously. All studies were conducted on Tifton loamy sand (fine-loamy, kaolinitic, thermic PlinthicKandiudults) with 86 to 88 sand, 8 silt, 4 to 6 clay, 0.5 to 1.3 organic matter, and pH ranging from 6.3 to 6.9.

Partners

It was reported that development of legume-rhizobia symbiosis may be tolerant to the presence of elevated concentrations of HMs in soils. The T. repens plants cultivated in soil, originated from mining site and extremely polluted with 220 g g-1 Cd, 30000 g g-1 Pb and 20000 g g-1 Zn, had healthy nodules and their potential for nitrogen fixation (80 g N ha-1 h-1) was high (Rother et al., 1983). However as a rule, nodulation and symbiotic nitrogen fixation was sensitive to HMs and inhibited in polluted soils, resulting in nitrogen deficiency and plant growth limitation. For example, significant reduction of nodule formation and nitrogen fixation caused by elevated HM concentrations was described for Glycine max (Chen et al., 2003), Leucaena leucocephala (Cheung et al., 2000), Lotuspurshianus (Wu and Lin, 1990) and Lupinus albus (Pastor et al., 2003). Moreover, it was proposed to use nodulation process as a bioindicator to test the toxicity of HM polluted soils (Neuman et al., 1998 Manier...

Aging and weathering

Metal ions (Cd, Cu and Zn) that are toxic to sensitive crops (shown in hydroponic experiments references given), like alfalfa (pZn 5.0-5.4) or wheat (pCu 8.2). In summarizing their results, the authors conclude that although Fe hydroxides may be an important sink for long-term metal retention and have been successfully used to remediate metal-contaminated soils, they may fail to lower activities of some trace metals, including Cu, to reach the U. S. EPA permitted metal loadings (e. g. for sludge aplication).

Terrestrial Systems

However, to characterise plant uptake of metals and their subsequent toxicity as a chemical equilibrium, as most current predictions of bioavailability (including the BLM) do, is an oversimplification. Living organisms may be in quasi-equilibrium with their environment, but plants grow toxicity can cause changes in uptake and accumulation processes, and the organism itself may exert homeostatic control over metal distribution after binding, with the distribution pattern varying with species, or cultivars within species, as well as with exposure concentration. Metal concentrations in soil solution could be considered to exist in a quasi-equilibrium the selective removal of ions from soil solution, as well as bulk water uptake to satisfy transpiration needs, leads to dissociation of complexes to restore equilibrium among free and complexed metals. Thus, it is not surprising that in a study of conditional stability constants for Cu accumulation in durum wheat (Triticum aestivum cv....

Solvents

Burken and Schnoor (1998) looked at plant uptake of several organic compounds, including solvents such as TCE. They did not look extensively for metabolites of the compounds, but rather at the uptake rates and transpiration of the chemicals by hydroponically exposed poplar cuttings. As expected, the uptake and transpiration rates corresponded to the vapor pressure of the compound, with compounds such as benzene and TCE showing the highest transpiration phyto-volatilization rates. Dietz and Schnoor (2001) looked at the relative toxicity of various chlorinated ethanes and ethenes, and determined that more chlorinated compounds had greater toxicity to poplar cuttings. Ma and Burken (2003) expanded previous volatilization studies (Vroblesky et al. 1999) by showing that poplars volatilize significant amounts of TCE through the stems of the plants in addition to leaf volatilization. Baduru et al. (2008) again looked at volatilization from poplar stems and trunks, and determined that there...

Petroleum

Storage tanks in the United States, an estimated 20 -35 may be leaking. As a result, BTEX or MTBE contamination is more frequently found in subsurface environments, primarily groundwater. As BTEX components have moderate log Kow values, significant entry into vegetation via the transpiration stream can be expected. Once in the plant, metabolism, storage, or evaporation could result (Collins et al. 2002). As such, many studies involving BTEX and MTBE use high transpiration volume or phreatophytic plants similar to those discussed above for solvents (poplar, willow) such species not only accumulate or remediate some degree of the contamination but also provide effective plume control. In a hydroponic study suggesting significant in-plant metabolic potential, Burken and Schnoor (1998) reported that 9 18 of the BTEX components were released from the transpiration stream and less than 5 were retained within the tissues. Although a variety of soil microorganisms have been isolated with...

Field Conditions

Therefore, applying the solution by irrigation has to be discussed. Drip irrigation would highly increase the costs of application. A possible way could be sprinkler irrigation which is cheaper. Anyhow, here the disadvantage remains that the solution cannot be applied directly to the soil and therefore salt could remain unproductive on the leaves. To overcome this limitation the solution would have to be applied either before rain or irrigation of water after the solution application would have to be performed.

Soil Science

External coupling processes of soil involves the interaction with atmosphere (liquid, particulate and colloidal phases wet and dry deposition), with hydrosystems (liquid, particulate and colloidal phases (deposition and resuspension), and with organisms (input by organic matter, output by bioaccumulation processes). In terrestrial contaminated areas, the soil has a key role for the investigation of the patterns resulted from external coupling because its turnover time is much lower than that of the biological, hydrological, and atmospheric entities, but higher enough to allow the detection of patterns as a result of these interactions at the scale of human observation. Soil is a more reactive entity than bedrock, for instance, with much higher reactive surfaces because of its fragmentary structure. The reactive inorganic parts in the soil are minerals and organic carbon, whose importance is underlined by their use in soil classification. The soil as physical multiphase entity (solid,...

Hydrology

From this disciplinary field, we refer here only on some aspects of surface hydrology, mainly catchment hydrology. The entities assumed in hydrology are hydrosystems, thus entities restricted to the aquatic phases, considered separated from their solid environment, which however controls water movements. The concept of hydro-system includes implicitly external ontological assumptions by the relations of the water with entities determining the types of flows at different scales. In the area of hydrology the distribution across scales of the processes is well documented (Bloeschl and Sivapalan 1995 Bloeschl 2001). Clear is also the fact that in the water quality modeling currently there are no models operating at multiple space-time scales, the integration of processes occurring at different scale being possible only by including separate models in common GIS-type platform (Srivastava et al. 2007). This is due to the coupling between processes of different scale generating...

Richard G Haverkamp

If the emphasis is changed from using plants to collect and concentrate a valuable element from soil, to the plant as a processing agent to convert an element from one chemical or physical form to another (for example from a metallic salt to a metal nanoparticle) then it is sensible to provide the elements for processing. It is also preferable to therefore grow the plants hydroponically, which enables very good control of the solution concentrations of metallic ions available to the plant. Hydroponic growth also enables very high concentrations of metals in plants to be achieved. Silver concentrations in plants grown hydroponically increase rapidly in the first few hours (Haverkamp and Marshall, 2009) to reach a maximum after less than 24 hours for Brassica juncea and perhaps 48 hours for Medicago sativa depending on the hydroponic concentration of silver (Harris and Bali, 2008). Plants have been shown to be able to accumulate silver to concentrations in the whole plant of up to 12.4...

Phytoremediation

Nevertheless, the persistence of all isomers was found to be lower in cropped plots of maize (Zea mays), wheat (Triticum sp.) or pigeon pea (Cajananus cajan) than in uncropped plots, therefore sustaining the idea of remediation of polluted sites with plants 66 . Revision of available literature concerning contamination of the aerial part of plants reveals that the a, P and y isomers have been detected in many plants, including Lactuca sativa (lettuce), Sesamum indicum (sesame), Hydrilla verticillata (hydra), Lagernia siceraira (bottle gourd), Memordica charantia (bitter gourd), Luffa cylindrical (sponge gourd), Citrullus varifistulosus (tinda punjab), Spinacia oleracea (spinach) and Brassica campestris (rape). These species were not selected for testing in hydroponics however, since the detected residues were due to a direct contact with lindane, and not as a result of translocation from roots to shoots. Barriada-Pereira et al. 67 also attributed the presence of lindane in the shoots...

Background

Soil Plant Atmosphere Continuum

Accumulation of metals by roots in a hydroponic setup, followed by harvesting of the plant biomass, is termed rhizofiltration Dushenkov and Kapulnik, 2000 . The accumulation of metals in shoot tissue, followed by harvesting of shoot biomass, is called phytoextraction Blaylock and Huang, 2000 . After harvesting of the root and or shoot biomass, the plant material may be ashed, followed by recycling of the metals if economically feasible Chaney et al., 2000 , or the disposal of the ash in landfill. Alternatively, the plant material may be used for non-food purposes, for example, cardboard or wood products.

Rhizosphere Ecology

With supplementation of autoclaved roots. Conversely, gnotobiotic hydroponic and sand-grown roots did not increase the rate of 2,4-D degradation, which suggested that the stimulatory component was both a function of the plant and cultivation medium. The authors also found evidence that unfractionated legume rhizodeposits enhanced 2,4-D mineralization. The implication was that flavonoids, as major signalling components of the rhizobia-legume symbiosis 1 , might select for microorganisms capable of detoxifying and utilising the flavanoid signals or their metabolites 66 . For example, cinnamic acid is one of the possible metabolites of flavanoid degradation and has been shown to induce TfdA, the gene responsible for the first step of 2,4-D catabolism 66 . 2,4-D is structurally analogous to p-coumaryl alcohol, a lignin monomer, which has been proposed to be a natural inducer of PCB degradation (Figures 3 and 4) 26 .

Biological Methods

Several plant-based experimental systems have been studied for phytoremediation purposes. In increasing order of complexity, they are plant cell cultures such as callus and cell suspensions (Harvey et al., 2002), differentiated organ cultures such as roots, hairy roots and shoots (Mackova et al., 2001 Suresh et al., 2005 Singh et al., 2006), explants such as leaf disks and excised roots and whole plants in hydroponic culture, in potted soil under greenhouse cultivation and in the field (Flocco et al., 2002 Singh et al., 2008 Schroder et al., 2008 Doran, 2009). It is important to note that plant tissue cultures cannot represent or simulate many aspects of whole plant cultivation, and a proper design of experiments and interpretation of results are required to avoid experimental artefacts and to obtain the maximum benefit from using plant tissue culture models. However, in vitro plant model systems have been a very useful tool for studying the uptake of organic compounds without the...

Growing Soilless

Growing Soilless

This is an easy-to-follow, step-by-step guide to growing organic, healthy vegetable, herbs and house plants without soil. Clearly illustrated with black and white line drawings, the book covers every aspect of home hydroponic gardening.

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