Showing papers by "North Eastern Hill University published in 1986"

Effect of herbicides butachlor, 2,4-D and oxyfluorfen on enzyme activities and CO2 evolution in submerged paddy field soil

Abstract: Effects of three herbicides 2,4-D, butachlor and oxyfluorfen on activities of dehydrogenase, urease and carbon dioxide evolution from paddy field soil were measured on weekly intervals. Dehydrogenase activity was significantly stimulated on application of herbicides. The herbicides did not affect the urease activity and the activity remained almost unchanged. The carbon dioxide output was higher in herbicide treated soil.

Complex peroxyuranates. Synthesis and structural assessment of alkali dioxoxperoxy(sulfato)aquouranates(VI), A2[UO2(O2)SO4(H2O)] (A = NH4, Na), and alkali dioxoperoxy(oxalato)uranate(VI) hydrates, A2[UO2(O2)C2O4].H2O

Abstract: Yellow microcrystalline alkali-metal and ammonium dioxoperoxy(sulfato)aquouranates(VI), A/sub 2/(UO/sub 2/(O/sub 2/)SO/sub 4/(H/sub 2/O)) (A = NH/sub 4/, Na), and alkali-metal and ammonium dioxoperoxy(oxalato)uranate(VI) hydrates, A/sub 2/(UO/sub 2/(O/sub 2/)C/sub 2/O/sub 4/).H/sub 2/O (A = NH/sub 4/, Na, K), have been synthesized from the reaction of the product obtained by treating an aqueous solution of UO/sub 2/(NO/sub 3/)/sub 2/.6H/sub 2/O with alkali-metal or ammonium hydroxide, AOH, with 30% H/sub 2/O/sub 2/ and aqueous sulfuric acid and oxalic acid solution, respectively, in the mole ratio UO/sub 2/(NO/sub 3/)/sub 2/.6H/sub 2/O:H/sub 2/O/sub 2/:SO/sub 4//sup 2 -/ or C/sub 2/O/sub 4//sup 2 -/ of 1:111:5 or 1, at pH 6 maintained by the addition of the corresponding alkali-metal or ammonium hydroxide. Precipitation was completed by the addition of ethanol. IR and laser Raman spectra suggest that the O/sub 2//sup 2 -/ and SO/sub 4//sup 2 -/ ions in (UO/sub 2/(O/sub 2/)SO/sub 4/(H/sub 2/O))/sup 2 -/ are bonded to the UO/sub 2//sup 2 +/ center in a bridging and in a monodentate manner, respectively, while both the O/sub 2//sup 2 -/ and C/sub 2/O/sub 4//sup 2 -/ ions in (UO/sub 2/(O/sub 2/)C/sub 2/O/sub 4/)/sup 2 -/ bind the uranyl center in bidentate chelated fashion. The complex peroxyuranatesmore » are diamagnetic and insoluble. The A/sub 2/(UO/sub 2/(O/sub 2/)SO/sub 4/(H/sub 2/O)) compounds, unlike A/sub 2/(UO/sub 2/(O/sub 2/)C/sub 2/O/sub 4/).H/sub 2/O, are stable up to 110 /sup 0/C. Whereas H/sub 2/O in A/sub 2/(UO/sub 2/(O/sub 2/SO/sub 4/(H/sub 2/O)) is coordinated to the UO/sub 2//sup 2 +/ center, it occurs as a water of crystallization in the corresponding peroxy oxalato compounds. 20 references, 3 tables.« less

Physico-chemical aspects of calcium vanadate apatite

Abstract: By appropriate modifications of existing precipitation methods, a sample of calcium vanadate apatite, Ca10(VO4)6(OH)2 was prepared at 110°C. It was characterized through X-ray, electron microscopic, infrared and thermoanalytical analyses in addition to chemical analysis. Equilibrating the sample in buffered aqueous media at 37° C, the solubility was measured using microanalytical techniques of Ca2+ and VO4 3− present in the saturated solutions after separating the colloidal component of the solute. Duration of equilibration for the attainment of saturation of the solution of the sample was obtained from a study on its dissolution kinetics. The pK ip of calcium vanadate apatite was found to be 107.09. The investigation showed that pK ip was independent of the presence of the common ions.

Effect of vinyl groups on resonance Raman spectra of protoporphyrin-IX

Abstract: Resonance Raman (RR) spectra obtained with several excitation wavelengths are compared for the following porphyrin-IX compounds: free-base protoporphyrin-IX, meso-porphyrin-IX and haematoporphyrin-IX and copper-protoporphyrin-IX and copper-mesoporphyrin-IX dimethyl esters. Certain bands in the RR spectra of all the free-base porphyrins or copper complexes are unaffected with respect to frequency, whereas there is a shift in the frequencies of some vibrational modes in some systems. From a comparative study of the systems which have identical geometrical arrangements, no extra features were found in the RR spectra of protoporphyrin which can be attributed directly to the vinyl group modes. This suggests that the vibrational modes of vinyl groups do not distort the excited electronic state substantially, and are not effective in vibronic coupling with the electronic states of the porphyrin macrocycle and therefore do not gain intensity under resonance excitation. Most of the vibrational modes are strongly coupled and there are no extra distinct features in the RR spectra of PP which may be associated with selective vibrational coupling of the vinyl group modes with the porphyrin skeletal modes.

Absence of the glutamine-synthetase-linked methylammonium (ammonium)-transport system in the cyanobiont of Cycas-cyanobacterial symbiosis.

Abstract: Using the ammonium analogue (14)CH3NH 3 (+) , ammonium transport was studied in the cyanobiont cells freshly isolated from the root nodules of Cycas revoluta. An L-methionine-DL-sulphoximine (MSX)-insensitive ammonium-transport system, which was dependent on membrane potential (ΔΨ), was found in the cyanobiont. However, the cyanobiont was incapable of metabolizing exogenous (14)CH3NH 3 (+) or NH 4 (+) because of the absence of another ammonium-transport system responsible for the uptake of ammonium for assimilation via glutamine synthetase (EC 6.3.1.2). Such a modification seems to be the result of symbiosis because the free-living cultured isolate, Anabaena cycadeae, has been shown to possess both the ammonium-transport systems.

Theory of distortion-induced I.R. and Raman intensity of forbidden modes of molecular units in crystals

Abstract: Using the principles of group theory and approximation methods, a quantitative theory of distortion-induced infrared and Raman intensity due to forbidden modes of molecular units at non-polar site symmetries in crystals has been discussed. Among all forbidden modes only those which belong to , attain distortion induced activity (DIA) of first order where α ij/an is a component of anisotropic polarizability tensor; others attain higher order DIA and are hardly expected to be observed in I.R./Raman spectra due to their weak intensity.

Kinetics of reduction of copper(II) by sodium tetrahydroborate

Abstract: The kinetics of reduction of copper(II) ion by sodium tetrahydroborate in buffered aqueous solution have been investigated. The rate of the reaction is first order in the concentrations of each of the reactants. The activation parameters were evaluated and a plausible mechanism for the reduction of copper(II) ion is proposed.

Population regulation of Galinsoga ciliata (Raf.) Blake and G. parviflora Cav.: Effect of 2,4‐D application at different growth stages and light regimes

Abstract: Summary: Resume: Zusammenfassung Population behaviour of two sympatric annual weeds, Galinsoga ciliata (Raf.) Blake and G. parviflora Cav., which occur abundantly in hill agro-ecosystems and secondary successional communities of north-east India, was studied in response to light intensity and 2,4-D application. Survival and growth of the two weeds were adversely affected by reduction in light intensity and increased concentration of 2,4-D. G. ciliata was more susceptible to 2,4-D, whereas G. parviflora to decrease in light. Leaf area ratio in G. ciliata increased under low light regime while that in G. parviflora decreased. The increased concentration of 2,4-D caused more severe effect on both weeds. The effect was, however, modified by the light intensity and age of plant at which the herbicide was applied. The application of 2,4-D at seedling stage under the high light regime caused greater mortality and growth reduction in both weeds, while the herbicide application at flowering stage resulted in much reduced production of viable seeds. Reglementation des peuplements de Galinsoga ciliata (Raf.) Blake et G. parviflora Cav.: Effet de l'application de 2,4-D a differents stades vegetatifs et par des regimes lumineux varies Le comportement de peuplements de deux mauvaises herbes annuelles sympatriques, Galinsoga ciliata (Raf.) Blake et G. parviflora Cav., qui abondent dans les agro-ecosystemes de montagne ainsi que les communautes secondaires de succession dans le nord-est des Indes, a fait l'objet d'une etude par rapport a l'intensite lumineuse et aux applications de 2,4-D. Une luminosite moins intense, ainsi qu'une plus forte concentration de 2,4-D, a fait preuve d'une influence nefaste sur la croissance des deux adventices. G. ciliata s'est montre plus sensible envers le 2,4-D tandis que G. parviflora a reagi davantage a la diminution de lumiere. Chez G. ciliata, la proportion de superficie foliaire a augmente par un regime de faible luminosite tandis que chez G. parviflora elle a diminue. Une concentration plus importante de 2,4-D a augmente l'effet nefaste chez les deux especes. Cependant cet effet a subi des modifications selon la luminosite ainsi que l'âge de la plante au moment du traitement herbicide. Applique au stade plantule par une forte luminosite, le 2,4-D a provoque chez les deux adventices une mortalite et une reduction de croissance plus marquees, tandis qu'une application a la fleuraison a amene une baisse considerable dans le nombre de graines viables. Populationsregulation von Galinsoga ciliata (Raf.) Blake und G. parviflora Cav.: Wirkung von 2,4-D Applikationen auf verschiedene Wachstums-stadien unter verschiedenen Lichtbedingungen Es wurde die Populationsdynamik zweier einjahriger, in denselben Arealen vorkommenden Unkrauter, Galinsoga ciliata (Raf.) Bale und G. parviflora Cav., haufig in Agro-Oekosystemen und sekundaren Pflanzengesellschaften Nordost-Indiens vorhanden, in Bezug auf Einfluss von Licht und 2,4-D Applikation studiert. Das Ueberleben und das Wachstum der zwei Unkrauter wurde in gegensatzlicher Weise vonmay der Lichtintensitat und steigender 2,4-D Konzentration beeinflusst. G. ciliata war empfindlicher auf 2,4-D; G. parviflora, jedoch, gegenuber starker Belichtung. Wahrend die Blattflache von G. ciliata bei schwachem Lichtangebot zunahm, nahm sie bei G. parviflora ab. An beiden Unkrautern verursachten steigende 2,4-D Konzentrationen eine zunehmende Wirkung. Dieser Effekt wurde allerdings durch Lichteinfluss und Alter der Pflanzen bei der Herbizidan-wendung beeinflusst. 2,4-D Applikation im Keimlingsstadium und unter hohem Lichtangebot verursachte eine hohere Mortalitatsrate und eine starkere Wachstumsverringerung bei beiden Species, wahrend die Herbizidbehandlung auf bluhende Pflanzen eine stark verminderte Produktion lebensfahiger Samen zur Folge hatte.

Influence of endotrophic mycorrhizae on the fusarial wilt of Cassia tora L.

Abstract: The wilting of Cassia tora caused by Fusarium oxysporum was reduced significantly when inoculated with VAM Mycorrhizal fungi highly influenced growth stimulation of the seedlings The population of F oxysporum was reduced in the presence of VAM

Breeding behaviour of Solanum khasianum Clarke

Abstract: In nature, Solanum khasianumClarke (syn. S. variumDunal) is a self pollinated plant. However, artificial cross pollination is feasible when pollination is done around the time of anthesis, which is between 09.30 and 10.00. Due to prevalence of heterostyly bud selection has to be highly specific.

Regulation of ammonium/methylammonium transport by ammonium in the cyanobacterium Anabaena variabilis

Abstract: The ammonium transport system of Anabaena variabilis Kutz ATCC 29413 was studied with regard to its repression and derepression using [14C]-methylammonium as an analogue for ammonium. Whereas N2-grown cells showed an active ammonium transport system, the latter was repressed in ammonium-grown cells. Repression of the ammonium transport system by ammonium did not require ammonium assimilation or de novo protein synthesis, suggesting that ammonium itself was the repressor signal. The derepression of the ammonium transport system however, required de novo protein synthesis and glutamine synthetase activity.

The influence of VA mycorrhizae on the wilting of Albizia procera and Dalbergia sissoo

Abstract: The effect of pre-inoculation with VA mycorrhizae on Fusarium wilt of Albizia procera and Dalbergia sissoo was done in a green house trial. Inoculation with Fusarium spp. decreased plant growth compared to noninoculated controls. Mycorrhizal plants were significantly higher than nonmycorrhizal ones. In addition to plant growth, the disease severity caused by Fusarium spp. reduced significantly when inoculated with VA mycorrhizae. The lowest percentage of Fusarium spp. were found on plants when treated with VA mycorrhizae. The population of Fusarium spp. were higher in the rhizosphere of nonmycorrhizal roots. The P concentration in the leaves of mycorrhizal and nonmycorrhizal plants were higher in the absence of Fusarium spp.

Modification of NO−3 metabolism in heterocysts of the N2-fixing cyanobacterium Anabaena 7120 (ATCC27893)

Abstract: The utilization of NO−3, NO−2 and NH+4 was studied in whole filaments and isolated heterocysts of Anabaena 7120 (ATCC27893). NO−3- and NO−2-uptake were detectable in whole filaments but not in heterocysts, whereas NH+4-uptake was detectable in both. Activity of NO−3-reductase was present in cell-free extracts of whole filaments but not of heterocysts, whereas activities of NO−2-reductase and glutamine synthetase were present in both. NO−3-uptake and reductase activities could not be induced in heterocysts even after prolonged incubation in NO−3 medium. It is suggested that NO−3-metabolism in heterocysts is impaired due to a selective and irreversible loss of NO−3-uptake and reductase systems resulting in the abolition of competition for molybdenum cofactor (Mo-Co) and reductant between nitrogenase and NO−3-reductase, and an increase in glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase levels.

Laser Raman study of phase transformation in single crystals of cadmium fluorotitanate hexahydrate

Abstract: A detailed temperature-dependent Raman study of oriented single crystals of CdTiF6·6H2O down to 10 K was carried out in the regions of internal vibrations and lattice modes. The line width, frequency shift and intensities of the modes associated with the [Cd(H2O)6]2+ and [TiF6]2− octahedra show abrupt changes at temperatures around 200 and 80 K, respectively, and many doubly degenerate modes split into two components. These studies suggest that this system undergoes two structural phase transitions at 200 and 80 K. A mechanism for these phase transitions is suggested.

Adaptive growth strategy of Khasi pine (Pinus kesiya Royle ex Gordon)

Abstract: Three year old open grown pine saplings were selected Three whorls of shoots were begun in one year The species thus exhibits a recurrent flushing pattern Two orders of shoots were recognised on the main leader during the study period of one year Shoots produced at lower canopy levels attained less extension growth and fewer and shorter needles compared to shoots at higher canopy levels The growth characteristics of shoots indicated shade intolerant nature of the species The fascicles of 3 flushes appearing at different times of the year had different patterns of fall and life expectancy The adaptive strategy of the growth pattern with recurrent flushing and short longevity of the needles are discussed and related to faster growth rate ofPinus kesiya in an early successional environment

Ammonium and potassium fluoromonooxalatomanganates(II), A[MnF(C2O4)] (A = NH4 or K) and sodium fluoromonooxalatomanganate(II) dihydrate, Na[MnF(C2O4)] · 2H2O

Abstract: Light pink-white microcrystalline ammonium and potassium fluoromonooxalatomanganates(II), A[MnF(C2O4)] (A = NH4 or K), and sodium fluoromonooxalatomanganate(II) dihydrate, Na[MnF(C2O4)] · 2H2O, have been synthesized by two different methods. Either KMnO4 is reduced in the presence of 40% HF and alkali metal oxalate, A2C2O4 (A = NH4, Na or K), or MnO(OH) in 40% HF reacts with A2C2O4. Characterisation was made by elemental analyses, determination of oxidation states, magnetic susceptibility measurements and infrared spectral studies.

Preparation and characterisation of phosphate and arsenate apatites of barium and their solid solution

Abstract: Phosphate and arsenate apatites of barium and one of their solid solutions were prepared by a wet method and characterized by chemical, x-ray, infrared and thermogravimetric analyses. Chemical analysis gave the stoichiometry of the samples while x-ray and infrared studies confirmed the formation of a solid solution. The range of thermal stabilities of the samples was established through thermogravimetric analysis.

SCF perturbation calculations on metalloporphyrins

Abstract: The influence of metal ion on the oxidation and ionisation potentials of metalloporphyrins is investigated by the simple electrostatic model using SCF perturbation theory. The zero order wavefunctions are obtained from PPP and CNDO/2 methods. The wide variations in redox potentials with metal and the relative insensitivity of the optical transitions with metal are very well accounted for by the perturbation approach.