Almas Zaidi

Aligarh Muslim University, Koil, Uttar Pradesh, India

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Publications (69)48.39 Total impact

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    ABSTRACT: In order to optimize the crop production and hence, to achieve food security, synthetic fertilizers have largely been used in high input agronomic practices to offset major and sometimes minor nutrient deficiencies of soils with concomitant intensification in food production. When used repeatedly in horticultural practices, such environmentally un-friendly fertilizers have deleteriously impacted soil fertility and consequently, the crop productivity. Taking these threats into account, scientists are desperate to find inexpensive, environmentally benign and easy to operate options to overcome fertilizer toxicity problems. In this regard, plant growth promoting rhizobacteria (PGPR) have magnetize the agrarian communities due in part to their low cost, easy access and simple mode of application. Broadly, PGPR when used either alone or in consortia, have resulted in tremendous positive impact on horticultural production. Among horticultural crops, the interest in quality of vegetables in recent times among consumers has increased worldwide. The results of studies conducted so far worldwide on the impact of PGPR carrying numerous multi-functional plant growth promoting activities on horticultural crops especially vegetables grown distinctively in different production systems is discussed and considered. The review will conclude by identifying several PGPR for future researches aiming to improve the health and quality of vegetables grown in different production systems. Also, the findings presented here are likely to reduce the use of chemical fertilizers in horticultural practices and to protect human health (via food chain) from the ill effect of fertilizers used in different agronomic environment.
    No preview · Article · Sep 2015 · Scientia Horticulturae
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    Full-text · Dataset · Jan 2015
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    ABSTRACT: Recently, nanoscience has become one of the most promising fields of research with greater impact on economy and environment health. The research on nanomaterials: materials of 100 nm in at least one dimension, is likely to result in the production of huge number of new nano-products in the coming years. Considering the importance of nanotechnology, a greater attention has been paid on this industry which is expected to reach a market size of approximately 2.6 trillion dollars by 2015 [1]. In addition, nanotechnology is also likely to influence agricultural research especially in (i) the conversion of agricultural and food wastes to energy and other useful by-products through enzymatic nano-bio-processing (ii) disease prevention and treatment of plants using various nanomaterials [2] and (iii) reproductive science and technology. Despite these benefits, the increasing numbers of commercial products, from cosmetics to medicine and fertilizers to crop products are adding sufficient amounts of nanomaterials ultimately to soils. Such nanoparticles have however, been found highly resistant to degradation and persist in soil or water bodies. Nanomaterials for example carbon nanotubes [3, 4], graphene-based nanomaterials [5], iron-based nanoparticles [6], silver [7] and copper, zinc and titanium oxide nanoparticles [8, 9] have been reported to cause biologically undesirable toxic effects on both deleterious and beneficial rhizosphere microorganisms [10-12] including Escherichia coli, Bacillus subtilis, and Streptococcus aureus [13], Pseudomonas chlororaphis [14-18], Pseudomonas putida [11] and Campylobacter jejuni [19]. However, the reports on the effect of nanoparticles on secondary metabolites of microbes are conflicting. For example, Dimkpa et al. [16] in a recent study found that sub-lethal levels of CuONPs reduced the secretion of plant growth promoting substance siderophore in P. chlororaphis O6 whereas ZnO NPs increased the production of the fluorescent siderophore pyoverdine. Similarly, a contrasting effect of CuO and ZnO NPs on siderophores and IAA has also been reported by Dimpka et al. [18] suggesting that the effect of NPs on secondary metabolite production by bacterial populations cannot be generalized rather it is highly metabolite/nano specific and may vary from Symbiotic nitrogen fixing rhizobia besides fixing atmospheric nitrogen also produces plant growth promoting substances such as indole acetic acids, siderophores, and cyanogenic compounds etc. However, the effects of nanomaterials on plant growth regulating substances synthesized by these bacteria are not reported. In this paper we have examined the impact of varying concentration of three metal oxide nanoparticles (MONPs) namely copper oxide (CuO), iron oxide (Fe2O3) and zinc oxide (ZnO) on growth behaviour and plant growth promoting activities of nodule forming bacterium Rhizobium sp. strain OS1. The three MONPs tested in this study differentially affected the levels of plant growth regulating substances in a dose dependent manner which varied with species of each nanoparticle. A maximum reduction in indole acetic acid, hydrogen cyanide, ammonia and siderophores, expressed by Rhizobium sp. OS1 was observed at 150 µgml-1 each of CuO, Fe2O3 and ZnO. Iron oxide did not show any toxicity to siderophores. At 50 µgml
    Full-text · Article · Oct 2014
  • M. Oves · M.S. Khan · A. Zaidi · A.S. Ahmed · A. Azam
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    ABSTRACT: Symbiotic nitrogen fixing rhizobia besides fixing atmospheric nitrogen also produces plant growth promoting substances such as indole acetic acids, siderophores, and cyanogenic compounds etc. However, the effects of nanomaterials on plant growth regulating substances synthesized by these bacteria are not reported. In this paper we have examined the impact of varying concentration of three metal oxide nanoparticles (MONPs) namely copper oxide (CuO), iron oxide (Fe2O3) and zinc oxide (ZnO) on growth behaviour and plant growth promoting activities of nodule forming bacterium Rhizobium sp. strain OS1. The three MONPs tested in this study differentially affected the levels of plant growth regulating substances in a dose dependent manner which varied with species of each nanoparticle. A maximum reduction in indole acetic acid, hydrogen cyanide, ammonia and siderophores, expressed by Rhizobium sp. OS1 was observed at 150 μgml-1each of CuO, Fe2O3and ZnO. Iron oxide did not show any toxicity to siderophores. At 50 μgml-1, CuO induced the IAA production by 11% which decreased progressively with increasing concentrations. The synthesis of HCN and NH3was completely abolished when strain OS1 was grown with 150 μgml-1of all nanoparticles. Unlike plant growth promoting substances, the production of exo-polysaccharide increased gradually with increasing concentration of each MONPs by rhizobial strain. This study suggests that the nanoparticles of different functional groups affect the physiological expression of rhizobial species differently and it further opens up a new vistas to better understand the impact of nanoparticles on symbiotic interaction between rhizobia and legumes.
    No preview · Article · Oct 2014 · IIOAB Journal
  • Md. Saghir Khan · Almas Zaidi · Ees Ahmad
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    ABSTRACT: Phosphorus (P) is the second important key plant nutrient after nitrogen. An adequate supply of P is therefore required for proper functioning and various metabolisms of plants. Majority of P in soils is fixed, and hence, plant available P is scarcely available despite the abundance of both inorganic and organic P forms in soils. A group of soil microorganisms capable of transforming insoluble P into soluble and plant accessible forms across different genera, collectively called phosphate-solubilizing microorganisms (PSM), have been found as best eco-friendly option for providing inexpensive P to plants. These organisms in addition to supplying soluble P to plants also facilitate the growth of plants by several other mechanisms, for instance, improving the uptake of nutrients and stimulating the production of some phytohormones. Even though several bacterial, fungal and actinomycetal strains have been identified as PSM, the mechanism by which they make P available to plants is poorly understood. This chapter focuses on the mechanism of P-solubilization and physiological functions of phosphate solubilizers in order to better understand the ecophysiology of PSM and consequently to gather knowledge for managing a sustainable environmental system. Conclusively, PSM are likely to serve as an efficient bio-fertilizer especially in areas deficient in P to increase the overall performance of crops. © Springer International Publishing Switzerland 2014. All rights reserved.
    No preview · Article · Jul 2014
  • Almas Zaidi · Ees Ahmad · Md. Saghir Khan
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    ABSTRACT: Soilborne phytopathogens are one of the major problems in sustainable crop production world over. To alleviate the damaging impact of pathogens on crop yields, huge quantities of toxic chemicals especially pesticides are used in modern agronomic practices, which, however, are extremely destructive to the environment. The non-desirability of applying huge quantities of pesticides to soil due in part to residue problems, emergence of resistance among soil phytopathogens, and lack of pathogen-resistant crop varieties has forced researchers to find solutions to the increasing pesticides problems. To this end, biological control measures consisting of microbial preparations are considered a promising option to the use of expensive and environment disruptive pesticides. Microorganisms including plant growth-promoting rhizobacteria (PGPR) in general have been found to synthesize a wide array of metabolites with significant fungicidal and bactericidal capabilities. The use of phosphate-solubilizing (PS) microorganisms among PGPR has produced both direct and indirect effects on growth and development of plants. The PS microbes endowed with biocontrol activity manage the pathogens by one or simultaneous mechanisms of antibiosis, lysis, competition, and myco-parasitism and prevent the yield losses. Even though the literature on the physiological role of PS microorganisms in crop enhancement via P supply is adequately available, the information on the ability of such organisms in the control of phytopathogens is scarce. Here, different mechanisms utilized by PS organisms for plant disease suppression are discussed. It is envisioned that the PS bacteria in the near future are expected to reduce, if not completely eliminate, the use of pesticides in insect-pests management strategies. © Springer International Publishing Switzerland 2014. All rights reserved.
    No preview · Chapter · Jul 2014
  • Ees Ahmad · Almas Zaidi · Md. Saghir Khan
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    ABSTRACT: Phosphate-solubilizing microorganisms (PSM) including bacteria, fungi, and actinomycetes dwelling in soil or other environment, for example, rhizosphere, do play some vital roles in facilitating growth and development of legumes and cereal plants via one or simultaneous mechanisms. Phosphate-solubilizing microbes when applied in agricultural practices provide one of the major plant nutrients, phosphorus, to plants by transforming insoluble P into soluble and plant available forms. This practice of applying PSM for enhancing legumes and cereal production has been found inexpensive and in many cases a successful strategy of reducing fertilizer input in intensive agricultural practices. The advent of such an eco-friendly option in farming system holds greater promise for increasing the productivity of legumes and cereal crops. Here, an attempt is made in this chapter to highlight the role of PSM involving different microbial groups, used either alone or in combination, in the promotion of growth and yield of legumes and cereal crops in different production systems.
    No preview · Chapter · Jul 2014
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    ABSTRACT: Among heavy metals, chromium is a highly toxic nonessential metal found in different environmental settings. Chromium pollution has been reported worldwide, causes undeniable damage to microbes and plant genotypes, and is carcinogenic and genotoxic for humans. Of the two most common oxidative states, hexavalent chromium is relatively more deleterious than the less-mobile trivalent form of chromium. Chromium toxicity, however, can be reduced by employing various physicochemical and biological processes. Among biomaterials, apart from plants, use of plant-growth-promoting rhizobacteria has been found effective, inexpensive, and environmentally friendly. Plant-growth-promoting rhizobacteria alleviate the metal toxicity by adopting different strategies like biosorption and bioaccumulation, bioreduction to a less-toxic state, and chromate efflux. Some of these methods have been proposed as effective biological tools for removing chromium from contaminated locations. The interaction of chromium with plant-growth-promoting rhizobacteria and the bacterial-based management of chromium toxicity is reviewed and discussed. The detoxification of chromium by plant-growth-promoting rhizobacteria is likely to reduce the adversity of chromium to various agroecosystems and may serve as a good candidate for bacterial-based bioremediation of chromium-polluted soils.
    No preview · Article · May 2014
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    A Zaidi · M S Khan · M Ahemad · M Oves

    Full-text · Dataset · Feb 2014
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    A Zaidi · M S Khan · M Ahemad · M Oves

    Full-text · Dataset · Feb 2014
  • Ees Ahmad · Md. Saghir Khan · Almas Zaidi
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    ABSTRACT: Plant growth promoting rhizobacteria affects the overall performance of plants by one or combination of mechanisms. However, little information is available on how ACC deaminase secreting bacteria enhance crop production. The present study aimed at identifying ACC deaminase producing and phosphate solubilizing bacterial strains and to assess their plant growth promoting activities. Additionally, the effect of two ACC deaminase positive bacterial strains Pseudomonas putida and Rhizobium leguminosarum on pea plants was determined to find a novel and compatible bacterial pairing for developing efficient inoculants for enhancing legume production and reducing dependence on chemical fertilizers. The isolated bacterial cultures were characterized biochemically and by 16S rRNA sequence analysis. The plant growth promoting activities was determined using standard microbiological methods. The impact of P. putida and R. leguminosarum, on pea plants was determined both in pots and in field environments. Of the total 40 bacterial strains, strain PSE3 isolated from Mentha arvenss rhizosphere and RP2 strain from pea nodules produced ACC deaminase, solubilized insoluble phosphate, synthesized indole acetic acid, ammonia, cyanogenic compounds, exopolysaccharides and had antifungal activity. The dual inoculation of P. putida strain PSE3 and R. leguminosarum strain RP2 had largest positive effect and markedly increased the growth, symbiotic characteristics, nutrient pool and quantity and quality of pea seeds. The measured parameters were further augmented when inoculated pea plants were grown in soils treated with urea or DAP. A significant variation in the measured parameters of pea plants was observed under both pot and field trials following microbial inoculation but the bacterial cultures did not differ significantly in growth promoting activities. The results suggest that ACC deaminase positive bacterial cultures endowed with multiple potential can be targeted to develop mixed inoculants for enhancing pea production and hence, to reduce dependence on synthetic fertilizers.
    No preview · Article · Oct 2013 · Symbiosis
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    ABSTRACT: Phosphorus (P) is one of the major plant nutrients whose deficiency results in severe losses to crop yields. To achieve optimum crop production, P is, therefore, consistently required. The use of chemical fertilizers in contrast is discouraged for two basic reasons: one, the repeated and injudicious application may alter soil fertility by adversely affecting microbial composition and functions and, second, it is expensive. To address these problems, scientists have identified soil-borne microorganisms belonging to a specific functional group generally referred to as phosphate-solubilizing microorganisms (PSM) which play many ecophysiological roles, especially in providing plants with P. They can be found in any environment from conventional to contaminated ones and are able to express their activity both in vitro and under field conditions. The solubilization of P by bacteria including even some of the strict nitrogen fixers, for example, rhizobia (symbiotic) or Azotobacter (asymbiotic), is a multifactor process. The ability to release bound P from both organic (enzymatic) and inorganic (acidification) sources by this functionally diverse group of organisms and to provide growth regulators (phytohormones) to plants or protecting plants from various diseases through other mechanisms (such as synthesizing antibiotics, siderophores, cyanogenic compounds, etc.) is indeed some of the most fascinating biological traits that have resulted in increased crop yields. Here, we highlight the functional aspects of PS bacteria especially their role in crop improvement particularly legumes and cereals grown in varied agro-ecological regions. The discussion attempted here is likely to serve as a low-cost prospective option for sustainable agriculture and also to solve economic constraint to considerable extent faced by the farming communities.
    No preview · Chapter · Jun 2013
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    ABSTRACT: Pseudomonas aeruginosa strain OSG41, isolated from the heavy metal contaminated water irrigated to rhizospheric soil of mustard crop, tolerated chromium up to the concentration of 1800 μg ml−1 and reduced it by 100% at pH 6–8 after 120 h incubation at 30–40 °C. P. aeruginosa produced plant growth-promoting substances, both in the presence and absence of chromium; it produced 32 μg ml−1 indole acetic acid ml−1, in Luria Bertani broth with 100 mg tryptophan ml−1, solubilized tri-calcium phosphate (417 μg ml−1) and secreted 20.8 μg ml−1 exopolysaccharides (EPS) which decreased with increasing concentration of chromium added to growth medium. While investigating the impact of hexavalent chromium on chickpea, chromium application to soil had a phytotoxic effect. The application of P. aeruginosa strain OSG41 even with three times concentration of chromium increased the dry matter accumulation, symbiotic attributes (like nodule formation), grain yield and protein of chickpea compared to non-inoculated plants. The bio-inoculant decreased the uptake of chromium by 36, 38 and 40% in roots, shoots and grains, respectively. The present finding suggests that the bioinoculant effectively reduced the toxicity of hexavalent chromium to chickpea plants and concurrently enhanced the biological and chemical characteristics of chickpea, when grown in chromium treated soils.
    Full-text · Article · May 2013 · European Journal of Soil Biology
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    ABSTRACT: The study was navigated to examine the metal biosorbing ability of bacterial strain OSM29 recovered from rhizosphere of cauliflower grown in soil irrigated consistently with industrial effluents. The metal tolerant bacterial strain OSM29 was identified as Bacillus thuringiensis following 16S rRNA gene sequence analysis. In the presence of the varying concentrations (25-150 mgl(-1)) of heavy metals, such as cadmium, chromium, copper, lead and nickel, the B. thuringiensis strain OSM29 showed an obvious metal removing potential. The effect of certain physico-chemical factors such as pH, initial metal concentration, and contact time on biosorption was also assessed. The optimum pH for nickel and chromium removal was 7, while for cadmium, copper and lead, it was 6. The optimal contact time was 30 min. for each metal at 32 ± 2 °C by strain OSM29. The biosorption capacity of the strain OSM29 for the metallic ions was highest for Ni (94%) which was followed by Cu (91.8%), while the lowest sorption by bacterial biomass was recorded for Cd (87%) at 25 mgl(-1) initial metal ion concentration. The regression coefficients obtained for heavy metals from the Freundlich and Langmuir models were significant. The surface chemical functional groups of B. thuringiensis biomass identified by Fourier transform infrared (FTIR) were amino, carboxyl, hydroxyl, and carbonyl groups, which may be involved in the biosorption of heavy metals. The biosorption ability of B. thuringiensis OSM29 varied with metals and was pH and metal concentration dependent. The biosorption of each metal was fairly rapid which could be an advantage for large scale treatment of contaminated sites.
    Full-text · Article · Apr 2013 · Saudi Journal of Biological Sciences
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    ABSTRACT: Biofabricated metal nanoparticles are generally biocompatible, inexpensive, and ecofriendly, therefore, are used preferably in industries, medical and material science research. Considering the importance of biofabricated materials, we isolated, characterized and identified a novel bacterial strain OS4 of Stenotrophomonas maltophilia (GenBank: JN247637.1). At neutral pH, this Gram negative bacterial strain significantly reduced hexavalent chromium, an important heavy metal contaminant found in the tannery effluents and minings. Subsequently, even at room temperature the supernatant of log phase grown culture of strain OS4 also reduced silver nitrate (AgNO3) to generate nanoparticles (AgNPs). These AgNPs were further characterized by UV-visible, Nanophox particle size analyzer, XRD, SEM and FTIR. As evident from the FTIR data, plausibly the protein components of supernatant caused the reduction of AgNO3. The cuboid and homogenous AgNPs showed a characteristic UV-visible peak at 428 nm with average size of ∼93 nm. The XRD spectra exhibited the characteristic Bragg peaks of 111, 200, 220 and 311 facets of the face centred cubic symmetry of nanoparticles suggesting that these nanoparticles were crystalline in nature. From the nanoparticle release kinetics data, the rapid release of AgNPs was correlated with the particle size and increasing surface area of the nanoparticles. A highly significant antimicrobial activity against medically important bacteria by the biofabricated AgNPs was also revealed as decline in growth of Staphylococcus aureus (91%), Escherichia coli (69%) and Serratia marcescens (66%) substantially. Additionally, different cytotoxic assays showed no toxicity of AgNPs to liver function, RBCs, splenocytes and HeLa cells, hence these particles were safe to use. Therefore, this novel bacterial strain OS4 is likely to provide broad spectrum benefits for curing chromium polluted sites, for biofabrication of AgNPs and ultimately in the nanoparticle based drug formulation for the treatment of infectious diseases.
    Full-text · Article · Mar 2013 · PLoS ONE
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    ABSTRACT: This title discusses various effects of heavy metal exposure to legumes as well as the bioremediation potential of rhizosphere microbes. Availability of heavy metals, their uptake and the effects of metals on various signaling pathways within legumes are presented. Furthermore, the effects of heavy metals to nitrogen fixing microorganisms and how microsymbionts can overcome metal stress is presented in detail. The role of nitrogen fixers in decontamination of heavy metal toxicity, mycoremediation of metal contaminated soils, microbially mediated transformation of heavy metals and action of plant growth promoting rhizobacteria and nitrogen fixers together in detoxifying heavy metals are broadly explained. This volume is a useful tool for scientists, policy makers and progressive legume growers intending to develop safe and healthy legumes for future generations.
    No preview · Article · Jan 2012
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    Ees Ahmad · Zaidi A · Khan MS · Oves M

    Full-text · Chapter · Jan 2012
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    ABSTRACT: Pollution of the environment by toxic metals in recent years has accelerated dramatically due to rapid industrial progress. Heavy metals when taken up in amounts in excess of the normal concentration produce lethal effects on plants, on microbes, and directly or indirectly on the human health. Deleterious impact of metals on plants includes the reduction in germinability of seeds, inactivation of enzymes, damage to cells by acting as antimetabolites, or formation of precipitates or chelates with essential metabolites. Heavy metals also show unconstructive effects on other physiological processes like photosynthesis, gaseous exchange, water relations, and mineral/nutrient absorption by plants. These adverse effects may be due to the generation of reactive oxygen species which may cause oxidative stress. The impact of heavy metals on germination of legume seeds and different physiological events of plants with special reference to leguminous plants grown in distinct agroecological niches is highlighted.
    No preview · Chapter · Jan 2012
  • Mohammad Oves · Khan MS · Almas Zaidi · Ees Ahmad
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    ABSTRACT: Globally, rapidly increasing industrialization and urbanization have resulted in the accumulation of higher concentrations of heavy metals in soils. The highly contaminated soil has therefore become unsuitable for cultivation probably because of the deleterious metal effects on the fertility of soils among various other soil characteristics. In addition, the uptake of heavy metals by agronomic crops and later on consumption of contaminated agri-foods have caused a serious threat to vulnerable human health. Considering these, a genuine attempt is made to address various aspects of metal contamination of soils. In addition, the nutritive value of some metals for bacteria and plants is briefly discussed. Here, we have also tried to understand how heavy metals risk to human health could be identified. These pertinent and highly demanding discussions are likely help to strategize the management options by policy makers/public for metal toxicity caused to various agro-ecosystems and for human health program.
    No preview · Chapter · Jan 2012
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    ABSTRACT: Heavy metal contamination resulting from rapid industrialization and other sources is a growing problem worldwide. Increasing pollution of soils with heavy metals disturbs the microbial biodiversity, soil fertility, and plant production and may cause significant human health problems. The excessive accumulation of heavy metals within plant tissues can modify protein structure or replace an essential element causing chlorosis, growth impairment, browning of roots, and photosystems dysfunction. To circumvent metal toxicity, bioremediation, a process that involves the use of biological materials to detoxify the contaminated sites and brings the environment to its contaminant free (original) state, has emerged as a promising alternative to widely practiced physicochemical methods used to clean up contaminated lands. Biological materials used to remediate contaminated sites are inexpensive, are easy to operate, do not produce hazardous by-products, and can be effective even if metals are present in low concentrations. Here, we integrate the knowledge obtained so far on the removal of metals and metalloids employing bioremediation strategies for contaminated soils. The information regarding different types of bioremediation and the challenges facing bioremediation are highlighted. The role and impacts of plant-growth-promoting rhizobacteria on bioremediation efficiency are addressed.
    No preview · Chapter · Jan 2012