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...     

Morphology and mechanical properties of sisal fibre/vinyl ester composites

Sisal fibres were subjected to a 2 % sodium hydroxide solution treatment for 2, 5 and 8 h at 35 °C. Change in chemical composition of the alkali treated fibres in comparison to that of the untreated fibres was evaluated. Fibres were characterized with respect to its FTIR, linear density, crystallinity, tenacity, modulus and % breaking strain. Tenacity of the fibres increased initially and then decreased as the time of alkali treatment was increased. Modulus of elasticity of the fibres increased with increase in alkali treatment time. Fibres lost breaking strain (%) gradually with increase in treatment time. Variation in mechanical properties of composites was studied with respect to the duration time of alkali treatment of fibres. The failure mode was particularly investigated before and after treatment for better understanding of the effect of alkali treatment.     

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.     

A rapid,novel and high-throughput identification of putative bell pepper transformants generated through in planta transformation approach

The recent progress on bell pepper transformation through in planta approach is incredibly simple with high transformation efficiencies in indigenous varieties. This method produces chimeric primary transformants (T₀) hence, a large number of T₀ plants and an efficient high throughput screening strategy is necessary to be developed. In the present investigation, we have standardized a rapid and highly efficient method of screening putative bell pepper transformants. Bell pepper transformants harbouring gfp genes was developed using in planta approach and 1050 etiolated T₁ seedlings were screened using fluorescent microscope to select GFP positive plants. The molecular analysis such as, gene specific PCRs, semiquantitative RT-PCR and Southern blots analysis corroborated the transgene integration in selected T₁ transformants. Based on progressive selection strategy, the transformation efficiency was 27.4% in gfp screened plants. The fluorescence based screening is viable, rapid, requires minimal labour, expense, and expertise with less percent of non-transformant escapes; further, this method can be extended from bell pepper to other crops to identify putative transformants developed through in planta approach.     

Effect of temperature on cortical infection by Plasmodiophora brassicae and clubroot severity

A study was conducted to assess the effect of temperature on infection and development of Plasmodiophora brassicae in the root cortex of Shanghai pak choy (Brassica rapa subsp. chinensis) and on subsequent clubroot severity. Ten-day-old seedlings were grown individually, inoculated with resting spores, and maintained in growth cabinets at 10, 15, 20, 25, and 30?C. Seedlings were harvested at 2-day intervals, starting 8 days after inoculation (DAI) and continuing until 42 DAI. Roots were assessed at 4-day intervals for the incidence of cortical infection and stage of infection (young plasmodia, mature plasmodia, and resting spores), at 2-day intervals for symptom development and clubroot severity, and at 8-day intervals for the number of spores per gram of gall. Temperature affected every stage of clubroot development. Cortical infection was highest and symptoms were observed earliest at 25?C, intermediate at 20 and 30?C, and lowest and latest at 15?C. No cortical infection or symptoms were observed at 42 DAI in plants grown at 10?C. A substantial delay in the development of the pathogen was observed at 15?C. Resting spores were first observed at 38 DAI in plants at 15?C, 26 DAI at 20 and 30?C, and 22 DAI at 25?C. The yield of resting spores from galls was higher in galls that developed at 20 to 30?C than those that developed at 15?C over 42 days of assessment. These results support the observation in companion studies that cool temperatures result in slower development of clubroot symptoms in brassica crops, and demonstrate that the temperature has a consistent pattern of effect throughout the life cycle of the pathogen.     

Importance and genetic diversity of vegetable-infecting tospoviruses in India

A survey for Peanut bud necrosis virus (PBNV), Watermelon bud necrosis virus (WBNV), Capsicum chlorosis virus (CaCV), and Iris yellow spot virus (IYSV) was conducted between 2002 and 2009 in the major vegetable-growing areas in India. PBNV was documented widely in tomato and chili peppers in 14 states representing southern, north-western, north-eastern, and central regions and WBNV was predominantly detected in watermelons and cucurbits in all except north-eastern regions. In addition, the expanded host range of PBNV to watermelons and other cucurbits and WBNV to tomato and chili peppers was observed leading to natural mixed infection of the two viruses. IYSV was found in onion in southern, central, and north-eastern regions and CaCV in tomato and chili peppers in northern and southern regions, respectively. Phylogenetic analysis of the nucleocapsid gene revealed segregation of field isolates of PBNV and WBNV into two distinct subclades, whereas isolates of CaCV and IYSV each clustered into a single clade. A proposal for establishing WBNV as a distinct tospovirus species is made based on the molecular characterization of small- (S) and medium- (M) RNA segments.     

Remediation of Perfluorooctane Sulfonate in Contaminated Soils by Modified Clay Adsorbent—a Risk-Based Approach

Perfluorooctane sulfonate (PFOS), which has numerous uses besides being an ingredient in the formulation of aqueous film-forming foams, is considered as an emerging pollutant of increasing public health and environmental concern due to recent reports of its worldwide distribution, environmental persistence and bioaccumulation potential. In an attempt to recommend a ‘risk-based’ remediation strategy, this study investigates the removal of PFOS from impacted waters and fixation of PFOS in impacted soils using a novel modified clay adsorbent (MatCARE?, patent number 2009905953). Batch adsorption tests demonstrated a much faster adsorption kinetics (only 60 min to reach equilibrium) and remarkably higher PFOS adsorption capacity (0.09 mmol g^?1) of the MatCARE? compared to a commercial activated carbon (0.07 mmol g^?1). Treatability studies, performed by treating the PFOS-contaminated soils with the MatCARE? (10 % w/w) and then incubating at 25 and 37 °C temperatures maintaining 60 % of the maximum water holding capacity of the soils for a period of a year, demonstrated a negligible release (water extractable) of the contaminant (only 0.5 to 0.6 %). The fixation of PFOS in soils by the new adsorbent was exothermic in nature. Soils with higher clay and organic matter content, but lower pH values, retained PFOS to a much greater extent. A cost analyses confirmed that the MatCARE^TM could be an economically viable option for the ‘risk-based’ remediation of PFOS in contaminated waters and soils.     

Carbondioxide gating in silk cocoon

Silk is the generic name given to the fibrous proteins spun by a number of arthropods. During metamorphosis, the larva of the silk producing arthropods excrete silk-fiber from its mouth and spun it around the body to form a protective structure called cocoon. An adult moth emerges out from the cocoon after the dormant phase (pupal phase) varying from 2 weeks to 9 months. It is intriguing how CO(2)/O(2) and ambient temperature are regulated inside the cocoon during the development of the pupa. Here we show that the cocoon membrane is asymmetric, it allows preferential gating of CO(2) from inside to outside and it regulates a physiological temperature inside the cocoon irrespective of the surrounding environment temperature. We demonstrate that under simulating CO(2) rich external environment, the CO(2) does not diffuse inside the cocoon. Whereas, when CO(2) was injected inside the cocoon, it diffuses out in 20 s, indicating gating of CO(2) from inside to outside the membrane. Removal of the calcium oxalate hydrate crystals which are naturally present on the outer surface of the cocoon affected the complete blockade of CO(2) flow from outside to inside suggesting its role to trap most of the CO(2) as hydrogen bonded bicarbonate on the surface. The weaved silk of the cocoon worked as the second barrier to prevent residual CO(2) passage. Furthermore, we show that under two extreme natural temperature regime of 5 and 50 °C, a temperature of 25 and 34 °C respectively were maintained inside the cocoons. Our results demonstrate, how CO(2) gating and thermoregulation helps in maintaining an ambient atmosphere inside the cocoon for the growth of pupa. Such natural architectural control of gas and temperature regulation could be helpful in developing energy saving structures and gas filters.     

Morpho-physiological parameters associated with iron deficiency chlorosis resistance and their effect on yield and its related traits in groundnut

Iron deficiency chlorosis (IDC) causes a significant reduction in yield of groundnut grown in calcareous and alkaline soils in India. The main aim of the study was to assess genotypic differences for morpho-physiological parameters associated with IDC resistance across different stages and their effect on yield and its related traits. The factorial pot experiment was comprised of two major factors, i) soil-Fe status [normal-Fe, deficit-Fe], and ii) genotypes [five] with differential IDC response, constituting 10 treatments. They were assessed for five morpho-physiological parameters associated with IDC resistance across five crop growth stages and also yield and its related traits. Associations between these traits were also estimated. Under deficit-Fe conditions, IDC resistant genotypes recorded significantly lower visual chlorosis rating (VCR), higher SPAD values, active Fe, chlorophyll content, peroxidase activity, and high yield compared to susceptible ones. Between normal- to deficit-Fe soils, resistant compared to susceptible genotypes showed no change in VCR scores; a lower reduction in SPAD, chlorophyll, active Fe, peroxidase activity, and pod yield. Under deficit-Fe conditions, high yield among resistant genotypes could be attributed to higher seed weight, number of pods and haulm yield, while contrasting reduction in main stem height and number of primaries. The results indicate that for initial large-scale screening of groundnut genotypes for IDC resistance, SPAD values are most ideal while active Fe could be utilized for confirmation of identified lines.