Browsing by Author "S. Verma"

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Agroinsecticide-induced Clastogenicity in Vicia faba L. Varieties
(Bellwether Publishing, Ltd., 2015) Vandana; S. Verma; B.R. Chaudhary
Cytological karyotyping of Vicia faba L. varieties, viz., IC-526385, IC-424900, IC-391651, and IC-361499, procured from Indian Agricultural Research Institute (IARI), New Delhi, India, revealed disomic (2 n = 12) and asymmetric nature of faba beans. Chromosome structural variations, including total chromatin length (TF %), interestingly noted in V. faba varieties, provided karyological validation of the varietal divergence. An attempt was made here to evaluate clastogenic response of the two commonly used farm insecticides, i.e., malathion and rogor, to select relatively more resistant varieties to these pesticides and to ascertain adequate dose(s) for safe administration of the said insecticides avoiding pollution load in the environment. Root-tips from treated seeds as well as the flower buds from sprayed plants exhibited a wide spectrum of chromosomal abnormalities, such as laggards, micronuclei, disturbed phases, bridges, fragments, and stickiness in a dose-dependent manner. Rogor was more genotoxic than malathion in all cases. Interestingly, however, lower dose (0.1%) of malathion registered a stimulatory effect on the growth of Vicia faba plants. Based on this study, V. faba IC-526385 (most resistant) cultivar and malathion (less clastogenic) insecticide can be recommended for use in farming. Copyright © Taylor & Francis Group, LLC.
Assessment of future changes in high-impact precipitation events for India using CMIP6 models
(Springer, 2023) Namendra Kumar Shahi; Shailendra Rai; S. Verma; R. Bhatla
The main focus of this study is on the high-impact precipitation events of the Indian summer monsoon (ISM) that trigger devastating floods and landslides and cause widespread damage to lives, agriculture, and infrastructure. Here, 16 models from Coupled Model Intercomparison Project Phase 6 (CMIP6) have been used to evaluate the projected changes in the spatio-temporal distribution of high-impact/extreme precipitation events for the ISM under a high-emission scenario during 1941–2070 with respect to the historical period of 1981–2010. The observed rain gauge-based precipitation datasets from two sources (i.e., the India Meteorological Department (IMD) and the Climate Prediction Center (CPC)) have been used to analyze the ability of CMIP6 models in simulating the extreme precipitation characteristics of the ISM for the historical period. After a comprehensive assessment analysis, it was found that four out of a total of 16 CMIP6 models performed well in simulating the spatio-temporal distribution of extreme precipitation characteristics of the ISM for the historical period. Relative future changes in the spatio-temporal distribution of extreme precipitation characteristics with respect to the historical period indicate that the frequency, intensity, and spatial extent of high-impact precipitation events will increase with global warming over large parts of India. In particular, the total number of extreme events above the 99th percentile of the reference period is projected to increase by over 60% with a robust increase in the spatial extent of the number of extreme events in central India. The number of days with more than 50 mm of precipitation is projected to rise at a rate of over 40% per season over large parts of India and a robust amplification of heavy precipitation has also been observed. The projected changes are more prominent in the central India region. Overall, our results show a significant contribution of global warming in the rise of the frequency and intensity of extreme precipitation events. Furthermore, the response to global warming is plausibly consistent among the selected models which provides greater confidence in the results and suggests the need for profound adaptation measures and better policy-making in the future. © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.
Changes in ploidy and its effect on thymoquinone concentrations in nigella sativa l. Seeds
(Headley Brothers Ltd, 2015) V. Dixit; S. Verma; B.R. Chaudhary
Colchicine-induced changes in ploidy levels provide an opportunity to improve the morphological and biochemical attributes of plants. Concentrations of metabolites have been shown to be affected by changing the ploidy level of the genome. Nigella sativa L. has long been used as a traditional spice and a medicinal herb, and recent scientific reports have increased its pharmaceutical and industrial applications. Ploidy effects were investigated following the application of 0.025, 0.05, or 0.10% (w/v) colchicine, and several changed levels of ploidy (aneuploidy, triploidy, or tetraploidy) were scored. The aneuploid seedling had one telocentric chromosome missing and did not survive beyond the juvenile stage. Triploids and tetraploids exhibited large-scale morphological characteristics such as thicker and darker-green leaves, and increased numbers of branches compared to diploid plants. Increased ploidy improved the morphogenetic behaviour of the tetraploid plants, but these plants exhibited stalk-lodging at maturity. Most of the triploid plants recovered by losing the extra chromosomes from their genome in succeeding generations, with the effect that seed-set returned to normal, as in the diploids. Other triploid plants did not set C2 seed. Tetraploid plants also revealed low levels of segregation in the C2 and later generations. Careful selection and screening, based on morphological and biochemical characteristics, established 32 tetraploid lines of N. sativa with approx. 46% higher concentrations of thymoquinone in the oil of their seed. © 2015, Headley Brothers Ltd. All rights reserved.
Effect of cadmium on soluble sugars and enzymes of their metabolism in rice
(2001) S. Verma; R.S. Dubey
The effect of cadmium on the content of starch and sugars, and changes in the activities of the enzymes of sugar metabolism were studied in growing seedlings of rice (Oryza sativa L.) cultivars Ratna and Jaya. During a 5- to 20-d exposure at 100 μM or 500 μM Cd(NO3)2 in the growth medium an increase in the content of total soluble sugars and reducing sugars, and decrease in the content of non-reducing sugars was observed. Cd-induced increase in the sugar content was greater in shoots than in roots. No definite pattern of changes in starch content or in α-amylase activity was observed. Presence of 100 or 500 μM Cd(NO3)2 increased the activities of sucrose degrading enzymes, acid invertase and sucrose synthase, whereas the activity of sucrose phosphate synthase declined.
Evaluation of CORDEX- South Asia regional climate models for heat wave simulations over India
(Elsevier Ltd, 2021) Saumya Singh; R.K. Mall; J. Dadich; S. Verma; J.V. Singh; A. Gupta
The episodes of heat wave events have strengthened in recent decades causing great concern for human health, agriculture and natural ecosystem. In the present study, Regional Climate Models (RCMs) namely, CCAM and RegCM, from Coordinated Regional Climate Downscaling Experiments (CORDEX) for South Asia (SA) are evaluated for simulating heat waves (March–June) for a long-term period (1971 to 2005) over India in comparison with observations from India Meteorological Department (IMD). The statistical analysis (correlation, RMSE, MAE, ECDF) results reveal differences in RCMs in simulating spatial pattern and trends of maximum temperature before bias correction. Variance scaling bias correction is found to remove bias and improve model simulations in capturing temperature variability. An increase in correlation in daily observations from 0.24 to 0.70 and reduction in RMSE from 8.08 °C to 2.02 °C and MAE from 3.87 °C to 2.43 °C after bias correction is observed between model and observation. LMDZ4 and GFDL-ESM2M are found to perform best in simulating interannual variability of seasonal mean maximum temperature with an underestimation of −7.74% and −15.41% which improved significantly to around −1.51% and − 0.78%, respectively after bias correction over India. LMDZ4 and GFDL-ESM2M are also best-performing models in significantly reproducing the heat wave frequency and spatial variability in closer proximity with observations over India amongst all models after bias correction. Over NW and western regions, the LMDZ4 and GFDL-ESM2M ensemble models successfully capture the increasing trend of 0.2 events/year and 0.4 events/year accordance to IMD and IITM criteria, respectively. However, the ACCESS1.0, CNRM-CM5 and CCSM4 ensemble experiments overestimated heat waves by ±40 events in most sub-divisions in India. Over the central Indian regions, the ACCESS 1.0 and CNRM-CM5 model output show a negative trend of −0.2 events/year and large spatial variability possibly due to model associated uncertainties. Overall the results show an improvement in capturing maximum temperature and heat waves across the regions of Indian sub-continent in the bias-corrected downscaled CORDEX-SA ensemble RCMs than without bias-corrected output. The study suggests a way forward to assess RCMs performance and uncertainty in extreme weather analysis in future projections. © 2020 Elsevier B.V.
Fission time scale from pre-scission neutron and α multiplicities in the O 16 + Pt 194 reaction
(American Physical Society, 2017) K. Kapoor; S. Verma; P. Sharma; R. Mahajan; N. Kaur; G. Kaur; B.R. Behera; K.P. Singh; A. Kumar; H. Singh; R. Dubey; N. Saneesh; A. Jhingan; P. Sugathan; G. Mohanto; B.K. Nayak; A. Saxena; H.P. Sharma; S.K. Chamoli; I. Mukul; V. Singh
Pre- and post-scission α-particle multiplicities have been measured for the reaction O16+Pt194 at 98.4 MeV forming Rn210 compound nucleus. α particles were measured at various angles in coincidence with the fission fragments. Moving source technique was used to extract the pre- and post-scission contributions to the particle multiplicity. Study of the fission mechanism using the different probes are helpful in understanding the detailed reaction dynamics. The neutron multiplicities for this reaction have been reported earlier. The multiplicities of neutrons and α particles were reproduced using standard statistical model code joanne2 by varying the transient (τtr) and saddle to scission (τssc) times. This code includes deformation dependent-particle transmission coefficients, binding energies and level densities. Fission time scales of the order of 50-65 ×10-21 s are required to reproduce the neutron and α-particle multiplicities. © 2017 American Physical Society.
Growth and biochemical profile of two cyanobacteria affected by carpet industry effluent
(1999) R.K. Rai; S. Verma; M. Goyle
The mesophillic cyanobacteria Anabaena flos-aquae and Synechococcus cedrorum were grown in various concentrations of carpet industry effluent collected from Bhadohi District of U.P., India. The changes in growth and biochemical profile were studied. The effluent was stimulatory for the growth of both the cyanobacteria when used between 5% to 50% concentrations. Anabaena flas-aquae showed maximum stimulation of growth at 25% concentration while for Synechacoccus cedrorum the concentration was 50%. These two species of cyanobacteria could be grown even in 100% concentration, but the growth was very poor. In all stimulatory levels of effluent, these cyanobacteria also showed increase in various macromolecule contents of the cell, i.e., chlorophyll, carotenoids, phycobilliprotiens, proteins and carbohydrates. Out of the two cyanobacteria studied, S. cedroruni was found to be more tolerant to the effluent.
Induction of ascorbate and guaiacol specific peroxidases in metal and water deficit induced oxidative stress in rice seedlings
(2006) P. Sharma; A.B. Jha; S. Verma; R.S. Dubey
Plants possess two distinguished forms of peroxidases, namely ascorbate peroxidase (APX) and guaiacol peroxidase (GPX). The contribution of both forms was studied in rice seedlings as part of defense mechanism against water deficit as well as metal imposed oxidative stress. The metals Pb2+ and As3+ were freely absorbed by roots of rice plants from growth medium in sand cultures but were mainly localized in roots. Rice seedlings grown for 20 days in Hoagland nutrient solution in sand cultures containing either 500 μM and 1000 μM Pb2+, 80 μM and 160 μM Al3+ or 25 μM and 50 μM As3+ or when seedlings grown for 20 days in nutrient solution were subjected to 24 h water stress treatment of -0.5 MPa or -2.0 MPa showed elevated levels of lipid peroxides. Lipid peroxidation paralleled with increased APX activity in Pb2+, Al3+, As3+ as well as water stressed seedlings. Seedlings growing in presence of metal salts showed increased GPX activity, however GPX activity was higher in moderately water stressed (-0.5 MPa) seedlings and it declined with higher level (-2.0 MPa) of water stress. Induced activity of GPX and elevated level of lipid peroxidation were higher in roots compared to shoots however the induced activity of APX was higher in shoots. Two isoforms of APX when purified from leaves of 20 day grown rice seedlings showed very high affinity for H 2O2 and ascorbate and very little affinity for guaiacol. Activity staining in polyacrylamide gels revealed the induction of two new isoforms of GPX in roots of Al3+ as well as As3+ treated seedlings where as one new isoform of APX was induced in shoot of water and Al3+ stressed seedlings. Both ascorbate and guaiacol specific peroxidases appear to be important components of antioxidative defense mechanism under conditions of metal toxicity and water stress.
Membrane-damaging potential of natural L-(-)-usnic acid in Staphylococcus aureus
(2012) V.K. Gupta; S. Verma; S. Gupta; A. Singh; A. Pal; S.K. Srivastava; P.K. Srivastava; S.C. Singh; M.P. Darokar
The purpose of this investigation was to try to understand the antibacterial mechanism of L-(-)-usnic acid isolated for the first time from fruticose lichen Usnea subfloridana using clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA). The minimum inhibitory concentration (MIC) of L-(-)-usnic acid against the clinical isolates of MRSA and reference strain S. aureus MTCC-96 (SA-96) was in the range 25-50 μg/ml. Treatment of both reference and clinical strains (MRSA-ST 2071) with fourfold MIC concentrations (100-200 μg/ml) of L-(-)-usnic acid reduced the viability of cells without damaging the cell wall. However, the loss of 260 nm absorbing material and increase in propidium iodide uptake was observed in both of the strains. Similarly, a combined effect of L-(-)-usnic acid (25-50 μg/ml) and 7.5% NaCl resulted in a reduced number of viable cells within 24 h in comparison to the control. These observations clearly indicate that L-(-)-usnic acid exerts its action by disruption of the bacterial membrane. Further, in vivo efficacy showed that L-(-)-usnic acid significantly (p<0.001) lowered the microbial load of spleen at doses ranging from 1 to 5 mg/kg. Further, toxicity studies in infected mice at doses 20 times higher than the efficacious dose indicated L-(-)usnic acid to be safe. Paradoxically, L- (-)usnic acid exhibited changes in serum triglycerides, alkaline phosphatase (ALKP) and liver organ weight in the healthy mice administered with only 25 mg/kg body weight. The results obtained in this study showed that natural L-(-)- usnic acid exerts its antibacterial activity against MRSA by disruption of the cell membrane. Further, the natural L-(-)- usnic acid was found to be safe up to 100 mg/kg body weight, thereby, making it a probable candidate for treating S. aureus infections. © 2012 Springer-Verlag.
Regional climate model performance and application of bias corrections in simulating summer monsoon maximum temperature for agro-climatic zones in India
(Springer, 2020) R. Bhatla; D. Sarkar; S. Verma; P. Sinha; S. Ghosh; R.K. Mall
The present study evaluates the performance of Conformal-Cubic Atmospheric Model (CCAM) simulations downscaled from six global climate models (GCMs) (i.e., ACCESS1.0, CNRM-CM5, CCSM4, GFDL-CM3, MPI-ESM-LR, and NorESM-M) and Max Plank’s Regional Model (REMO2009(MPI)) obtained from the South-Asia Coordinated Regional Climate Downscaling Experiment (CORDEX) for analyzing the summer monsoon maximum temperature (Tmax) over the fifteen Agro-Climatic Zones (ACZs) in India. The model simulations are compared with the two sets of observed data obtained from the India Meteorology Department (IMD) and Climate Research Unit (CRU) for the period from 1981 to 2005. The results illustrate that the skill of CCAM regional climate models (RCMs) is higher than the REMO in simulating the Tmax over all the regions. The spatial patterns of Tmax in CCAM (CCSM) and CCAM (CNRM) are closer to IMD, while the Tmax distributions in CCAM (CNRM), CCAM (CCSM), and CCAM (BCCR) agree well with the CRU, and correlation coefficient (CC) is more than 0.6; however, large positive biases in all RCMs are depicted over the Himalayan regions. The inter-comparison among all the RCMs suggest that the CCAM (CNRM) and CCAM (CCSM) are rendering as the foremost models in simulating Tmax over different ACZs. Performances of these two models also infer the usefulness of the model products for impact studies over the individual ACZs. However, the existing systematic biases in the RCMs impeded the model performance and it is necessary to remove the model bias prior to some real-time application. In this study, two bias correction methods, i.e., linear scaling (LS) and distribution mapping (DM), have been used to correct RCM output bias. It is found that the model performance using DM correction is better than LS method. The performance validations are evaluated based on the probability density function (PDF), CC, and standard deviation (SD) with 95% confidence level. The model evaluation has also been justified using mean absolute error (MAE) index, Nash-Sutcliffe coefficient (NS) index, percent bias (Pbias), and the Willmott’s index of agreement (d) which confirm the research findings. The results are providing an effective guidance on the usefulness of bias corrected RCMs over a particular ACZs for impact assessment. © 2020, Springer-Verlag GmbH Austria, part of Springer Nature.
Role of viscosity in fusion-fission dynamics via simultaneously measured neutron and α -particle multiplicities
(American Physical Society, 2019) K. Kapoor; N. Bansal; Chetan Sharma; S. Verma; K. Rani; R. Mahajan; B.R. Behera; K.P. Singh; A. Kumar; H. Singh; R. Dubey; N. Saneesh; M. Kumar; A. Yadav; A. Jhingan; P. Sugathan; B.K. Nayak; A. Saxena; H.P. Sharma; S.K. Chamoli
The multiplicities of α particles and neutrons have been measured simultaneously for the reaction O16+Pt196 forming Rn212 compound nucleus at excitation energies of 56 MeV, 61 MeV, and 68 MeV. Neutrons and α particles were detected at various angles in coincidence with the fission fragments. To extract the contribution of pre- and postmultiplicities using the total α-particle and neutron spectra, moving source formalism was implemented. In the case of α particle, near scission contribution has also been extracted. Study of the fission mechanism using light particle emissions are helpful in understanding the detailed fusion-fission reaction dynamics. The statistical model code joanne2, which includes deformation-dependent particle transmission coefficients, binding energies and level densities, has been used to reproduce the measured multiplicities of neutrons and α particles by varying the transient (τtr) and saddle to scission (τssc) times. It is found that the fission time scales of the order of 50-70×10-21 sec are required to reproduce the neutron and α-particles multiplicities simultaneously. The fission time scales are the measure of the nuclear viscosity, which is responsible for the dynamic hindrance of the fission process. © 2019 American Physical Society.
Study of nuclear fusion-fission dynamics in 16O+194Pt reaction
(American Institute of Physics Inc., 2017) K. Kapoor; S. Verma; P. Sharma; R. Mahajan; N. Kaur; G. Kaur; B.R. Behera; K.P. Singh; H. Singh; R. Dubey; N. Saneesh; A. Jhingan; P. Sugathan; G. Mohanto; B.K. Nayak; A. Saxena; H.P. Sharma; S.K. Chamoli; I. Mukul; A. Kumar
Pre- and post-scission α-particle multiplicities have been measured for the reaction 16O + 194Pt at 98.4 MeV forming compound nucleus 210Rn. The α-particle's yield has been measured in coincidence with the fission fragments at various angles. The moving source analysis was performed to extract the alpha particle multiplicity which yielded the contribution of pre- and post- scission components. The pre-scission α-particle multiplicity has been compared with JOANNE2 statistical model code predictions to extract fission time scale and which is observed to be around 55zs (1zs=10-21s). © 2017 Author(s).