Genetic resource enhancement by isolation of diversegenotypes from seed progeny in predominantly sterile rose scentedgeranium Pelargonium graveolens

Four new accessions (BSP1-4) of rose scentedgeranium Pelargonium graveolens were derivedfrom the spontaneous half-sib seed progeny of mostly sterilepopulations of the cultivar accession Bipuli. The seed producingplants of Bipuli had been growing among the populations of cultivaraccessions Hemanti and Kunti in the temperate agroclimate ofKodaikanal, Tamilnadu in India. The four new accessions were comparedwith the cultivar accessions Bipuli, Hemanti and Kunti in fieldexperiments under subtropical agroclimate of Lucknow, Uttar Pradeshfor essential oil yield and quality related traits and in terms oftheir RAPD profiles. The crop yield and essential oil parameters andDNA profiles of the four new accessions and three cultivar accessionsallowed the conclusion that the accessions BSP-1, BSP-2 andBSP-3 were Bipuli × Kunti hybrids and BSP-4was a Bipuli × Hemanti hybrid. The accession BSP-4demonstrated hybrid vigour in several of the essential oil yieldrelated traits; on average basis it out yielded other accessions by afactor of about 2.4. The essential oil of BSP-4 had 89%rhodinol content in which citronellol to geraniol ratio was 1:1 andthe contents of isomenthone, menthone, 10-epi--eudesmol, 6,9-guaiadiene, decanoic acid andisodecanoic acid were relatively lower than in the oils of accessionsBipuli and/or Hemanti. The present study has shown a way for thegeneration of new genotypes in rose scented geranium in which thecultivars have been vegetatively maintained for decades and thegenetic resources are scanty.     

Bioavailability of an organophosphorus pesticide,fenamiphos, sorbed on an organo clay

Hydrolysis of an insecticide/nematicide, fenamiphos [ethyl-3-methyl-4-(methylthio)phenyl-(1-methylethyl)phosphoramidate], immobilized through sorption by cetyltrimethylammonium-exchanged montmorillonite (CTMA-clay) by a soil bacterium, Brevibacterium sp., was examined. X-ray diffraction analysis, infrared spectra, and a negative electrophoretic mobility strongly indicated that fenamiphos was intercalated within the bacterially inaccessible interlayer spaces of CTMA-clay. The bacterium hydrolyzed, within 24 h, 82% of the fenamiphos sorbed by the CTMA-clay complex. There was a concomitant accumulation of hydrolysis product, fenamiphos phenol, in nearly stoichiometric amounts. During the same period, in abiotic (uninoculated) controls, 4.6% of the sorbed insecticide was released into the aqueous phase as compared to 6.0% of the sorbed fenamiphos in another abiotic control where activated carbon, a sink for desorbed fenamiphos, was present. Thus, within 24 h, the bacterium hydrolyzed 77% more fenamiphos sorbed by organo clay than the amounts desorbed in abiotic controls. Such rapid degradation of an intercalated pesticide by a bacterium has not been reported before. Evidence indicated that extracellular enzymes produced by the bacterium rapidly hydrolyzed the nondesorbable fenamiphos, even when the enzyme itself was sorbed. Fenamiphos strongly sorbed to an organo clay appears to be readily available for exceptionally rapid degradation by the bacterium.     

Algal degradation of a known endocrine disrupting insecticide, alpha-endosulfan, and its metabolite, endosulfan sulfate, in liquid medium and soil

The role of algae in the persistence, transformation, and bioremediation of two endocrine disrupting chemicals, alpha-endosulfan (a cyclodiene insecticide) and its oxidation product endosulfan sulfate, in soil (incubated under light or in darkness) and a liquid medium was examined. Incubation of soil under light dramatically decreased the persistence of alpha-endosulfan and enhanced its transformation to endosulfan sulfate, over that of dark-incubated soil samples, under both nonflooded and flooded conditions. This enhanced degradation of soil-applied alpha-endosulfan was associated with profuse growth of indigenous phototrophic organisms such as algae in soil incubated under light. Inoculation of soil with green algae, Chlorococcum sp. or Scenedesmus sp., further enhanced the degradation of alpha-endosulfan. The role of algae in alpha-endosulfan degradation was convincingly demonstrated when these algae degraded alpha-endosulfan to endosulfan sulfate, the major metabolite, and endosulfan ether, a minor metabolite, in a defined liquid medium. When a high density of the algal inoculum was used, both metabolites appeared to undergo further degradation as evident from their accumulation only in small amounts and the appearance of an endosulfan-derived aldehyde. Interestingly, beta-endosulfan was detected during degradation of alpha-endosulfan by high density algal cultures. These algae were also capable of degrading endosulfan sulfate but to a lesser extent than alpha-endosulfan. Evidence suggested that both alpha-endosulfan and endosulfan sulfate were immediately sorbed by the algae from the medium, which then effected their degradation. Biosorption, coupled with their biotransformation ability, especially at a high inoculum density, makes algae effective candidates for remediation of alpha-endosulfan-polluted environments.     

Organoclays reduce arsenic bioavailability and bioaccessibility in contaminated soils

Purpose  

Naturally occurring layer silicate clay minerals can be value added by modifying their surface properties to enhance their efficacy in the remediation of environmental contaminants. Silicate clay minerals modified by the introduction of organic molecules into the mineral structure are known as organoclays and show much promise for environmental remediation applications. The present study assesses the extent of decrease in bioavailable and bioaccessible arsenic (As) via enhanced adsorption by soil treated with organoclays.     

Effect of Seaweeds on Degradation of DDT in Soils

There are concerns over the environmental risks posed by Cu-based fungicide use, and there is community and regulatory pressure on viticultural industries to restrict the use of Cu-based fungicides. This study assesses the relative environmental risks posed by Cu-based and alternative synthetic organic fungicide compounds used in Australian vineyards, giving particular consideration to their adverse effects on soil microbial activity and how risks vary across different viticultural regions. The study was guided by key steps in the ecological risk assessment framework to analyse the risks of Cu-based fungicides towards soil organisms and involved four key steps: (1) problem formulation, (2) analysis (characterise exposure and effects), (3) risk characterisation and (4) risk assessment. There is evidence of a build-up of Cu-based fungicide residues in Australian vineyard soils, although this has occurred over many years, thus allowing the availability of Cu in the soil to be attenuated over time due to aging processes. On the whole, it appears that Cu-based fungicide residues are currently unlikely to pose a significant risk to soil organisms in Australian vineyard soils. However, there are indicators that continued applications of Cu-based fungicides may well have implications on the use of impacted land for sustainable agricultural production. Further detailed studies are required to enable a more definitive characterisation of the risks posed by Cu-based fungicide residues, such as establishing a clearer link between the laboratory and agricultural settings, investigating effects on other indicators of microbial activity and biodiversity and understanding the resilience of soil microbes to additional stressors. The challenge for agricultural industries and governments, both in Australia and globally, is to formulate appropriate plans to reduce the risks associated with Cu-based fungicide use. Further research is required to consider the relative risks of a wide range of alternative fungicide compounds to ensure that they pose a lower environmental risk than the Cu-based fungicides they may replace.     

Toxicity of p-aminophenol and p-nitrophenol to Chlorella vulgaris and two species of Nostoc isolated from soil

An examination was made of the effects of p-aminophenol (PAP) treatment individually and in combination with its parent compound, p-nitrophenol (PNP), on growth and metabolic activities of a microalga, Chlorella vulgaris, and two cyanobacteria, Nostoc linckia and Nostoc muscorum, all isolated from soil. Comparatively, the cyanobacteria were more sensitive to the phenol treatments. All but the lowest (2 μg ml⁻¹) PAP treatments inhibited cell number, chlorophyll a, and total carbohydrate production, ¹⁴CO₂ uptake, and nitrate reductase and nitrogenase activity. The algistatic effect in C. vulgaris caused by PAP could not be reverted even in the presence of acetate (0.1%). However, the inherent toxic effect of PNP established toward the alga and cyanobacteria was found alleviated in the presence of PAP only at lower concentrations. Transmission electron microscopy revealed many cytological abnormalities in Chlorella vulgaris under the influence of the selected phenols, indicating that the toxicants directly interfere with membrane properties and enzymes.     

Relative Value of Phosphate Compounds in Reducing the Bioavailability and Toxicity of Lead in Contaminated Soils

Lead forms stable compounds with phosphate and the immobilized Pb becomes less available to soil biota. In this study, we tested the bioavailabilty of Pb using earthworms (Eisenia fetida) and plants after immobilization of Pb by a soluble P compound and an insoluble rock phosphate compound in the presence of phosphate-solubilizing bacteria (Enterobacter sp.). Rock phosphate in the presence of phosphate-solubilizing bacteria and a soluble P compound enhanced Pb immobilization as measured by NH₄NO₃-extractable Pb concentration, thereby reduced its bioavailability as evaluated by earthworm Pb loading and sunflower (Helianthus annuus) Pb uptake under greenhouse conditions. However, soluble P treatment increased the concentration of Pb in soil solution thereby inhibited the root elongation of mustard (Brassica hirta) seedlings. Sunflower plants in the Pb-spiked soil without P amendments showed symptoms of necrosis and stunting because of Pb toxicity. Both soluble and insoluble P treatments significantly increased shoot and root weight and decreased Pb concentration in shoot by more than 50% compared to the control. However, high Pb concentration in soil solution was found in soluble P treatment, which can be attributed to dissolved organic carbon–Pb complex formation, thereby increasing Pb mobility. The inoculation of phosphate-solubilizing bacteria can facilitate phytostabilization of Pb-contaminated site.     

Chronic and reproductive toxicity of cadmium,zinc, and lead in binary and tertiary mixtures to the earthworm (Eisenia fetida)

Journal of Soils and Sediments - The presence of one metal can alter the toxicity of another metal by having an additive, synergistic, or antagonistic impact. Mixed metal pollution has clear...     

Sodium Application Enhances DDT Transformation in a Long-Term Contaminated Soil

Bioremediation is an economically attractive option to remediate soil contaminated with DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane] and other organochlorine pesticides. However, lack of DDT bioavailability in soil presents one major obstacle to this technology particularly in soils that have been contaminated for long periods. In this work, sodium ion (Na⁺) was applied to a long-term DDT contaminated soil as Na⁺ is known to disperse clays, which would potentially release and/or expose physically protected DDT thereby enhancing DDT bioavailability. Sodium ion addition significantly increased dissolved organic carbon (DOC) levels, anaerobic bacterial numbers and the amount of DDT residues measured in soil solution. DDT transformation ranged from 95% (30—80 mg Na⁺ kg^-1 soil) to 72% (no Na⁺ added) with the optimum level of DDT transformation occurring at 30 mg Na⁺ kg^-1 soil. Higher Na⁺ levels repressed DDT transformation and this appeared to be related to lower DOC levels and flocculation of soils. The anaerobic incubation conditions employed (high water content) prevented DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene] production and DDD [1,1-dichloro-2,2-bis(p-chlorophenyl)ethane] was the major breakdown product formed. Overall it appeared that Na⁺ has potential as a cheap and safe alternative to surfactants as a method for increasing DDT transformation in contaminated soil.