11-01-2012, 01:57 PM
(This post was last modified: 11-01-2012, 05:49 PM by Administrator.)
The technique of utilization of biological agents for degradation of pollutants is known as bioremediation. Phytoremediation is a branch of bioremediation wherein plants are employed for the purpose of removal of pollutants from a specific area.
Plants aid in phytoremediation by absorption, assimilation of compounds, vaporization of pollutants, metabolic digestion, or by microbial degradation by plant associated microbes. The plants which can accumulate and degrade the contaminants are known as ‘hyperaccumulaters’ which play a major role in phytoremediation.
Different modes of Phytoremediation
Depending on the technique applied phytoremediation can be subdivided into many kinds:
(i) Phytoextraction: it refers to a process in which plants breakdown contaminants and adsorbs the same into its tissues. After adsorption, plants can be removed from site and disposed or incinerated. Different plant types have different ability of phytoextraction and the plants with most effectiveness are chosen usually. This process is mostly used for treatment of metal pollutants in soil.
(ii) Rhizofiltrtion: in this process the pollutants gets adsorbed and deposited, not on the shoot tissues but in this case, in the root or rather in the rhizosphere of plants. This technique is specifically employed for waste removal from contaminated water sources.
(iii) Phytostabilisation: this concept involves immobilization of the pollutants following absorption and adsorption of it by plant roots and finally precipitation of the pollutant in the root so that it does not migrate from soil into air or other sources.
(iv) Phytotransformation: it deals with transformation or degradation of pollutants as a result of various metabolic processes by plants. Thus it is also known as phytodegradation.
(v) Phytovolatilization : the contaminants are absorbed by plants, undergo many changes and finally gets volatized from leaf surface during transpiration process of plants.
(vi) Phytostimulation: the microbial population near the root system of plants gets induced by the presence of rhizosphere which initiates them to break down the pollutants. This process is also known as rhizosphere degradation.
Role of biotechnology in phytoremediation:
Off late, biotechnology has been found to increase its wide spectrum of applications into phytoremediation as well. Plants adopted for phytoremediation are usually found to exhibit the specific property due to the presence the special genes coding for it. These plants are usually seen in area where metal ores exist. The genes responsible for this resistance by such plants are isolated and expressed in wide variety of transgenic plants so that they can be made resistant as well. This increases the number of plant species that can be used for such purpose. It is also possible with the help of biotechnology to increase the gene expression for maximum resistance.
Certain plants are seen to show increased resistance under the presence of certain microbes. Biotechnology makes it possible to isolate such microbes and enrich the soil so as to enhance the phytoremediation by respective plants.
Examples of application of biotechnological aspects in phytoremediation
Selenium: The micronutrient selenium is known to induce toxicity in the soil where the concentration of the same is found to be high. It is found that methylation of amino acids at specific site can result in volatilization of selenium compound. Thus a transgenic plant is constructed which has the ability to volatize the same by following the guidelines of genetic engineering and utilizing the information obtained by studying hyperaccumulators of selenium.
Mercury: Mercury can be degraded by certain bacterium due to the presence of merA and merB genes. Thus integration of these genes into certain plant genomes has seen effective mercury degradation by such transgenic plants. The genes are targeted to be expressed in chloroplasts so that after degradation into relatively less toxic form, it is volatized. Thus transgenic tobacco produced by this phenomenon was shown to exhibit mercuric resistance.
Arsenic: Certain bacterial genes present in E. coli, such as ArsC is responsible for reduction of arsenic and formation of a complex in the presence of glutathione(GSH). An increased amount of GSH can be produced by expression of glutamyl cysteine synthetase enzyme. These genes are isolated and transferred to form a transgenic plant which can effectively absorb arsenic and accumulate the same in its vacuoles resulting in phytoremediation.
Thus it can be concluded that biotechnological tools can be utilized to improvise many existing phytoremediation systems yielding more effective and faster results.
Plants aid in phytoremediation by absorption, assimilation of compounds, vaporization of pollutants, metabolic digestion, or by microbial degradation by plant associated microbes. The plants which can accumulate and degrade the contaminants are known as ‘hyperaccumulaters’ which play a major role in phytoremediation.
Different modes of Phytoremediation
Depending on the technique applied phytoremediation can be subdivided into many kinds:
(i) Phytoextraction: it refers to a process in which plants breakdown contaminants and adsorbs the same into its tissues. After adsorption, plants can be removed from site and disposed or incinerated. Different plant types have different ability of phytoextraction and the plants with most effectiveness are chosen usually. This process is mostly used for treatment of metal pollutants in soil.
(ii) Rhizofiltrtion: in this process the pollutants gets adsorbed and deposited, not on the shoot tissues but in this case, in the root or rather in the rhizosphere of plants. This technique is specifically employed for waste removal from contaminated water sources.
(iii) Phytostabilisation: this concept involves immobilization of the pollutants following absorption and adsorption of it by plant roots and finally precipitation of the pollutant in the root so that it does not migrate from soil into air or other sources.
(iv) Phytotransformation: it deals with transformation or degradation of pollutants as a result of various metabolic processes by plants. Thus it is also known as phytodegradation.
(v) Phytovolatilization : the contaminants are absorbed by plants, undergo many changes and finally gets volatized from leaf surface during transpiration process of plants.
(vi) Phytostimulation: the microbial population near the root system of plants gets induced by the presence of rhizosphere which initiates them to break down the pollutants. This process is also known as rhizosphere degradation.
Role of biotechnology in phytoremediation:
Off late, biotechnology has been found to increase its wide spectrum of applications into phytoremediation as well. Plants adopted for phytoremediation are usually found to exhibit the specific property due to the presence the special genes coding for it. These plants are usually seen in area where metal ores exist. The genes responsible for this resistance by such plants are isolated and expressed in wide variety of transgenic plants so that they can be made resistant as well. This increases the number of plant species that can be used for such purpose. It is also possible with the help of biotechnology to increase the gene expression for maximum resistance.
Certain plants are seen to show increased resistance under the presence of certain microbes. Biotechnology makes it possible to isolate such microbes and enrich the soil so as to enhance the phytoremediation by respective plants.
Examples of application of biotechnological aspects in phytoremediation
Selenium: The micronutrient selenium is known to induce toxicity in the soil where the concentration of the same is found to be high. It is found that methylation of amino acids at specific site can result in volatilization of selenium compound. Thus a transgenic plant is constructed which has the ability to volatize the same by following the guidelines of genetic engineering and utilizing the information obtained by studying hyperaccumulators of selenium.
Mercury: Mercury can be degraded by certain bacterium due to the presence of merA and merB genes. Thus integration of these genes into certain plant genomes has seen effective mercury degradation by such transgenic plants. The genes are targeted to be expressed in chloroplasts so that after degradation into relatively less toxic form, it is volatized. Thus transgenic tobacco produced by this phenomenon was shown to exhibit mercuric resistance.
Arsenic: Certain bacterial genes present in E. coli, such as ArsC is responsible for reduction of arsenic and formation of a complex in the presence of glutathione(GSH). An increased amount of GSH can be produced by expression of glutamyl cysteine synthetase enzyme. These genes are isolated and transferred to form a transgenic plant which can effectively absorb arsenic and accumulate the same in its vacuoles resulting in phytoremediation.
Thus it can be concluded that biotechnological tools can be utilized to improvise many existing phytoremediation systems yielding more effective and faster results.
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