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Search Results: 1 - 10 of 490848 matches for " M.V2* and Sheshshayee "
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Assessment of Genetic Diversity across differentially adopted rice ecotypes
Sridevi, G1., Raju, B.R2., Mohankumar, M.V2* and Sheshshayee, M, S.
Electronic Journal of Plant Breeding , 2012,
Abstract: Rice is an important staple food and a rich source of carbohydrates for 90% of South and Southeast Asians. Geneticdiversity of naturally adopted upland lines along with few germplasm collections in Karnataka were studied basedon 13 SSR loci on chromosome 1. A total of 24 individuals belonging to 3 differentially adopted groups [Upland(8), landraces (8) and cultivated varieties (8)] had a moderate to high level of genetic variability at groups level withnumber of alleles ranging from 5 to 23 (average 11.5) and PIC from 0.51 to 0.94 (average 0.79). The heterozygosityvaried from 0.39 to as high as 0.70. Over all genetic diversity of 0.81 was revealed indicating a high level of geneticvariation among these individuals. At the similarity coefficient of 7, all the lines were clearly grouped in 3 clusters.All cultivated types grouped in one cluster (cluster 1) except Rasi and CTH 1 which were included in cluster 2 andcluster 3 respectively. Cluster 1 contained 9 cultivated genotypes, where as cluster 2 contained 11 land races andcluster 3 had 4 upland lines. Out of 4 upland lines one line (AC-35341) intermixed, with C1 and three lines (PS-229,JBT-37/4 and AC-35310) with C3. The study of SSR markers on chromosome 1 facilitated the classification of theselines according to their adaptability. The information about the genetics of these populations will be for specificchromosomes and will be very useful for rice breeding programs, especially for gene mapping and ultimately formarker assisted selection programs.
The Gas Phase HO-Initiated Oxidation of Furan: A Theoretical Investigation on the Reaction Mechanism
Josep M. Anglada(C2V)
The Open Chemical Physics Journal , 2008, DOI: 10.2174/1874412500801010080]
Abstract: The reaction mechanism of the gas-phase HO-initiated oxidation of furan has been investigated by means of high level theoretical methods. The reaction is a complex process that begins with the formation of a pre-reactive hydrogen bonded complex, previous to the addition of the HO radical to furan, forming the 2 and 3-HO-adducts. In the prereactive complex, the hydrogen bond is formed by interaction between the hydrogen of the hydroxyl radical and the π system of furan and its stability is computed to be 1.6 kcal·mol-1 (including the BSSE corrections). The 2 and 3-HO-adducts are computed to be 30.5 and 12.5 kcal·mol-1 respectively, more stable than the reactants. The transition state leading to the formation of the 2-HO-adduct lies below the energy of the separate reactants (0.5 kcal·mol-1) and the transition state producing the 3-HO-adduct that is computed to lie 3.4 kcal·mol-1 above the sum of the energies of furan and hydroxyl radical. There are four reaction paths for the ring-opening of the 2-HO-adduct, leading to the formation of different conformers of 4-hydroxybutenaldehyde radical. The most stable of these conformers presents a cyclic symmetric (C2V) structure and can be characterized as a low-barrier hydrogen bond. The geometry optimizations and characterizations done in this work were carried out at MP2/6-311G(d,p), MP2/6-311+G(2df,2p) and QCISD/6-311G(d,p) levels of theory, whereas the relative energies are obtained at CCSD(T)/cc-pVTZ level of theory.
Effect of incubation time and substrate concentration on N-uptake rates by phytoplankton in the Bay of Bengal
S. Kumar,R. Ramesh,S. Sardesai,M. S. Sheshshayee
Biogeosciences Discussions , 2005,
Abstract: We report here the results of three experiments, which are slight variations of the 15N method (JGOFS protocol) for determination of new production. The first two test the effect of (i) duration of incubation time and (ii) concentration of tracer added on the uptake rates of various N-species (nitrate, ammonium and urea) by marine phytoplankton; while the third compares in situ and deck incubations from dawn to dusk. Results indicate that nitrate uptake can be underestimated by experiments where incubation times shorter than 4h or when more than 10% of the ambient concentration of nitrate is added prior to incubation. The f-ratio increases from 0.28 to 0.42 when the incubation time increases from two to four hours. This may be due to the observed increase in the uptake rate of nitrate and decrease in the urea uptake rate. Unlike ammonium [y{=}2.07x{-}0.002, (r2=0.55)] and urea uptakes [y{=}1.88x{+}0.004 (r2=0.88)], the nitrate uptake decreases as the concentration of the substrate (x) increases, showing a negative correlation [y{=}-0.76x+0.05 (r2=0.86)], possibly due to production of glutamine, which might suppress nitrate uptake. This leads to decline in the f-ratio from 0.47 to 0.10, when concentration of tracer varies from 0.01 to 0.04μ M. The column integrated total productions are 519 mg C m-2 d-1 and 251 mg C m-2 d-1 for in situ and deck incubations, respectively. The 14C based production at the same location is ~200 mg C m-2 d-1, which is in closer agreement to the 15N based total production measured by deck incubation.
Balance del nitrógeno en el sistema suelo-planta con pasto Guinea (Panicum maximum Jacq) en condiciones de bosque seco tropical
Pirela1,M.F; Clavero2,T; Fernández2,L; Sandoval2,V L;
Revista de la Facultad de Agronomía , 2006,
Abstract: abstract in order to study the nitrogen balance on the soil-plant system wilth guinea grass (panicum maximum jacq), an essay was carried out in the western part ot venezuela. the area belongs to a tropical dry forest, with an average annual precipitation of 1200mm with average temperatures of 28oc. an experimental design with randomized blocks was used with five replications and three nitrogen levels n0 = 0 kg ha-1.year-1, n1 = 100 kg ha-1.year-1 and n2 =200 kg ha-1.year-1. the data was processed using pearson's correlation analysis. se evaluó el contenido de nitrógeno (n-total) en la planta, las pérdidas de nitrógeno por efecto de la precolación, escorrentía, el contenido de nitrógeno en el suelo y el aporte de nitrógeno por la lluvia. los resultados obtenidos muestran que la distribución porcentual del nitrógeno en la planta resulto en un 55% en la biomasa removida, un 35% en la biomasa residual y un 10% en la biomasa radicular. las pérdidas por percolación ocurrieron en un 80% como n-n03- y en un 20% como n-nh4+. las pérdidas por escorrentía resultaron muy peque?as con valores que no excedieron 1 kg ha-1.a?o-1. del nitrógeno en el agua de lluvia el n-nh4+ se constituye en el mayor aporte con 8,4 kg ha-1.a?o-1 mientras tanto, el n-n03- 8,4 kg ha-1.a?o-1 mientras un 66,8% y 33,2% respectivamente. were evaluated nitrogen's content (total-n) in the plant, nitrogen's lost by effect of percolation, run-off, and nitrogen's content in the soil and the nitrogen's provision by rain. the obtained results show that the percentage distribution of nitrogen in the plant was of 55% in the removed biomass, 35% on the residual biomass and 10% on the radicle biomass. lost by percolation occurred in 80%as in n -n03- and 20% as n-nh4+. lost by run-off were not too much, with values that did not exceed 1 kg ha-1.year-1. of the nitrogen if the rain water n-nh4+ constitutes the highest contribution with 8.4 kg ha-1.year-1 meanwhile, 4.16 kg n.ha-1.year-1 showing 66.8% and 33.2% respecti
Balance del nitrógeno en el sistema suelo-planta con pasto Guinea (Panicum maximum Jacq) en condiciones de bosque seco tropical Nitrogen's Balance in the soil-plant system with guinea-grass (Panicum maximum Jacq) in tropical dry forest
M.F Pirela1,T Clavero2,L Fernández2,V L Sandoval2
Revista de la Facultad de Agronomía , 2006,
Abstract: A objeto de estudiar el balance del nitrógeno en el sistema suelo - planta con pasto guinea (Panicum maximum Jacq) se llevo a cabo un experimento en el occidente de Venezuela. Area perteneciente a un Bosque Seco Tropical, con una precipitación promedio anual 1200mm con temperaturas promedios de 28°C. Se utilizó un dise o experimental en bloque al azar con cinco repeticiones y tres niveles de nitrógeno N0 = 0 kg ha-1.a o-1, N1 = 100 kg.ha-1.a o-1 y N2 =200 kg ha-1.a o-1. Los datos se procesaron utilizando el análisis de correlación de Pearson. Se evaluó el contenido de nitrógeno (N-Total) en la planta, las pérdidas de nitrógeno por efecto de la precolación, escorrentía, el contenido de nitrógeno en el suelo y el aporte de nitrógeno por la lluvia. Los resultados obtenidos muestran que la distribución porcentual del nitrógeno en la planta resulto en un 55% en la biomasa removida, un 35% en la biomasa residual y un 10% en la biomasa radicular. Las pérdidas por percolación ocurrieron en un 80% como N-N03- y en un 20% como N-NH4+. Las pérdidas por escorrentía resultaron muy peque as con valores que no excedieron 1 kg ha-1.a o-1. Del nitrógeno en el agua de lluvia, el N-NH4+ constituye el mayor aporte con 8,4 kg ha-1.a o-1 mientras tanto, el N-N03- aportó 4,16 kg ha-1.a o-1 representando un 66,8% y 33,2% respectivamente Abstract In order to study the nitrogen balance on the soil-plant system wilth guinea grass (Panicum maximum Jacq), an essay was carried out in the western part ot Venezuela. The area belongs to a Tropical dry Forest, with an average annual precipitation of 1200mm with average temperatures of 28oC. An experimental design with randomized blocks was used with five replications and three nitrogen levels N0 = 0 kg ha-1.year-1, N1 = 100 kg ha-1.year-1 and N2 =200 kg ha-1.year-1. The data was processed using Pearson's correlation analysis. Se evaluó el contenido de nitrógeno (N-Total) en la planta, las pérdidas de nitrógeno por efecto de la precolación, escorrentía, el contenido de nitrógeno en el suelo y el aporte de nitrógeno por la lluvia. Los resultados obtenidos muestran que la distribución porcentual del nitrógeno en la planta resulto en un 55% en la biomasa removida, un 35% en la biomasa residual y un 10% en la biomasa radicular. Las pérdidas por percolación ocurrieron en un 80% como N-N03- y en un 20% como N-NH4+. Las pérdidas por escorrentía resultaron muy peque as con valores que no excedieron 1 kg ha-1.a o-1. Del nitrógeno en el agua de lluvia el N-NH4+ se constituye en el mayor aporte con 8,4 kg ha-1.a o-1 mientras tanto, el N-N03- 8,4 kg
Nitrogen Uptake in the Northeastern Arabian Sea during Winter Cooling
S. Kumar,R. Ramesh,R. M. Dwivedi,M. Raman,M. S. Sheshshayee,W. D'Souza
International Journal of Oceanography , 2010, DOI: 10.1155/2010/819029
Abstract: The uptake of dissolved inorganic nitrogen by phytoplankton is an important aspect of the nitrogen cycle of oceans. Here, we present nitrate (NO3?) and ammonium (NH4
Nitrogen Uptake in the Northeastern Arabian Sea during Winter Cooling
S. Kumar,R. Ramesh,R. M. Dwivedi,M. Raman,M. S. Sheshshayee,W. D'Souza
International Journal of Oceanography , 2010, DOI: 10.1155/2010/819029
Abstract: The uptake of dissolved inorganic nitrogen by phytoplankton is an important aspect of the nitrogen cycle of oceans. Here, we present nitrate ( ) and ammonium ( ) uptake rates in the northeastern Arabian Sea using tracer technique. In this relatively underexplored region, productivity is high during winter due to supply of nutrients by convective mixing caused by the cooling of the surface by the northeast monsoon winds. Studies done during different months (January and late February-early March) of the northeast monsoon 2003 revealed a fivefold increase in the average euphotic zone integrated uptake from January (2.3?mmolN ) to late February-early March (12.7?mmolN ). The -ratio during January appeared to be affected by the winter cooling effect and increased by more than 50% from the southernmost station to the northern open ocean stations, indicating hydrographic and meteorological control. Estimates of residence time suggested that entrained in the water column during January contributed to the development of blooms during late February-early March. 1. Introduction The cycling of nitrogen (N) plays an important role in our environment and ecosystem. Primary production by photosynthesis is directly related to the N cycle and the productivity of many ecosystems is known to be controlled by N availability [1]. One of the important parameters in the N cycle of oceans is N uptake by phytoplankton, which depends on light and substrate availability [2] and acts as a regulator of primary and export production in the ocean. The part of primary production that is supported by external nitrogenous inputs of upwelled, riverine or aeolian origin introduced in the euphotic zone is known as new production, whereas regenerated production is defined as that part of the primary production which sustains on recycled nutrients like and urea, within the euphotic zone [3]. Classically, uptake is considered as new production and (and urea) uptake as regenerated production. The fraction of the total N uptake that is new is called the f-ratio and represents the probability that a N atom is assimilated by phytoplankton due to new production; likewise (1-f) is the probability of assimilation by regenerated production [4]. Due to its inextricable link with the export production, the proper understanding of new production and nutrient regime of different oceanic regions is of utmost importance in the global carbon cycle [5, 6]. The Arabian Sea constitutes the northwestern (NW) part of the Indian Ocean and encompasses an area of around [7]. Although the Arabian Sea is one of the
Nitrogen Uptake Rates during Spring in the NE Arabian Sea
Naveen Gandhi,R. Ramesh,R. Srivastava,M. S. Sheshshayee,R. M. Dwivedi,Mini Raman
International Journal of Oceanography , 2010, DOI: 10.1155/2010/127493
Abstract: We present new data on N uptake rates and f-ratios in the north-eastern (NE) Arabian Sea, where significant amounts of Trichodesmium were present in spring, 2006. The measured total nitrogen uptake rates ranged from 0.34 to 1.58 mmol N m?2d?1. N2 fixation associated with Trichodesmium varied from 0.002 to 0.54 mmol N m?2d?1 estimated from the abundance of Trichodesmium and specific N2 fixation rates of 1.5 pmol N trichome?1h?1. Inclusion of N2 fixation rates significantly changes f-ratios particularly in the coastal stations. Nitrogen isotopic data of surface suspended particles suggest that recently fixed nitrogen contributes as high as ~79% of the nitrogen in surface suspended particles. In addition, water column gained ~30 mmol N m?2 in the form of nitrate, likely due to nitrification of ammonium released by Trichodesmium. For better estimations, direct measurement of N2 fixation is recommended.
Nitrogen Uptake Rates during Spring in the NE Arabian Sea
Naveen Gandhi,R. Ramesh,R. Srivastava,M. S. Sheshshayee,R. M. Dwivedi,Mini Raman
International Journal of Oceanography , 2010, DOI: 10.1155/2010/127493
Abstract: We present new data on N uptake rates and f-ratios in the north-eastern (NE) Arabian Sea, where significant amounts of Trichodesmium were present in spring, 2006. The measured total nitrogen uptake rates ranged from 0.34 to 1.58 mmol N? . fixation associated with Trichodesmium varied from 0.002 to 0.54?mmol N estimated from the abundance of Trichodesmium and specific fixation rates of 1.5?pmol N trichome . Inclusion of fixation rates significantly changes f-ratios particularly in the coastal stations. Nitrogen isotopic data of surface suspended particles suggest that recently fixed nitrogen contributes as high as?~79% of the nitrogen in surface suspended particles. In addition, water column gained?~30 mmol N in the form of nitrate, likely due to nitrification of ammonium released by Trichodesmium. For better estimations, direct measurement of fixation is recommended. 1. Introduction Nitrogenous nutrients are considered to be the major limiting factor of oceanic primary production in many regions [1]. Further, primary production can be partitioned on the basis of the nitrogen source: “new” and “regenerated” production [2]. New production is supported by nitrate from the deeper ocean, rivers, and atmospheric N2??fixed by diazotrophs. However, ammonium and urea, derived from biological processes occurring within the euphotic zone, sustain regenerated production; these can circulate indefinitely under a quasisteady state or form an ideal closed system if there is no nitrogen loss from the euphotic zone. Losses through the sinking of particulate matter, mixing, and by predation by zooplankton invariably happen in the real ocean, and therefore other sources of nitrogen are needed to sustain productivity. It is important to determine if the sum of the losses, in the form of export production, is balanced by nitrate upwelling and N2??fixation by diazotrophs, and verify whether on an annual time scale export production is equal to the new production, under steady state [3]. The Arabian Sea (area ~6.2 × 106?km2), though accounts for only ~1% of the global ocean surface, contributes to ~5% of the global marine primary production [4]. Recent observations based on ocean color show that summer productivity in the western Arabian Sea has been increasing from year 1997 to 2004 [5]. The observed trend in Chl a has been attributed to the warming of the Eurasian land mass. However, such claims are not supported by in situ hydrographic and chlorophyll measurements as well as a reanalysis of ocean colour data extending to 2009 [6]. Further, such a trend is not observed in
Natural isotopic composition of nitrogen in suspended particulate matter in the Bay of Bengal
S. Kumar, R. Ramesh, N. B. Bhosle, S. Sardesai,M. S. Sheshshayee
Biogeosciences (BG) & Discussions (BGD) , 2004,
Abstract: We present the first measurement of nitrogen isotopic composition (δ15N) in suspended particulate matter (SPM) of the surface Bay of Bengal (BOB) at 24 different locations during pre- (April–May 2003) and post- (September–October 2002) monsoon seasons. The δ15N of particulate organic nitrogen (PON) in surface suspended matter of coastal as well as northern open BOB shows signatures of a two end-member mixing between continental inputs and marine sources. Dilution by the organic and detrital continental material brought in by rivers leads to consistently lower δ15N, evident from the relationship between surface salinity and δ15N. δ15N of surface PON of open ocean locations during both seasons, and also at coastal locations during pre-monsoon suggest the nitrate from deeper waters as a predominant source of nutrient for planktons. The depth profiles of δ15N of SPM during pre-monsoon season at nine different locations are also presented. These indicate an increase in δ15N by a maximum of 2.8‰ between euphotic depth and 300 m, which is lower than that observed in the eastern Indian Ocean, indicating the role of higher sinking rates of particles ballasted by aggregates of organic and mineral matter in BOB.
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