Showing papers by "North Eastern Hill University published in 1983"
TL;DR: The different species and infraspecific categories of the genus Brachionus, so far reported or described from India, are reviewed and remarks are made on the ecology and epizoic nature of various species.
Abstract: The different species and infraspecific categories of the genus Brachionus, so far reported or described from India, are reviewed. Their distribution and taxonomic validity are discussed. Remarks are made on the ecology and epizoic nature of various species.
62 citations
TL;DR: It was found that species ofTrichoderma, Aspergillus, Penicillium, Fusarium and a dark sterile species were the most common fungi among the initial mycoflora in the burnt soil, whereas NH4+−N increased rapidly after the burn.
Abstract: The effect of slash-burning on the soil microflora was investigated for a period of one year during 1979–80. Quantitatively, the microflora was drastically reduced in the burnt plot. The density of the fungal population reached to their original level within one month after burning, whereas for bacteria and actinomycetes it took about 20 days. The effect of fire was restricted to the surface layer of 0–2 cm and below this depth no effect of fire was observed. This will be dependent upon the intensity and duration of fire.
53 citations
TL;DR: In this article, the effect of "slash and burn" agriculture on soil fertility at higher elevations of Meghalaya, north-eastern India was investigated, comparing and contrasting 15, 10 and 5-year jhum cycles.
46 citations
TL;DR: In this article, the hydrology and the pattern of sediment and nutrient loss through water that may occur under "slash and burn" agriculture (jhum) at the time of cropping, as well as during the subsequent fallow development, was studied at higher elevations of Meghalaya, north-eastern India and compared with terrace cultivation.
45 citations
TL;DR: Results demonstrate that the enzyme activities, microbial population as well as most of the physico-chemical characteristics of soils followed the trend permanent agriculture on plain lands>terrace land agriculture>‘slash and burn’ type of shifting agriculture.
Abstract: Dehydrogenase and urease activities, bacterial and fungal populations and physicochemical characteristics of maize (Zea mays L.) field soils have been studied for one crop cycle. A comparison has been made among soils of three different agricultural systemsviz permanent agriculture on plain lands in valleys, recently introduced terrace land agriculture and age old ‘slash and burn’ type of shifting agriculture on slopes. Results demonstrate that the enzyme activities, microbial population as well as most of the physico-chemical characteristics of soils followed the trend permanent agriculture on plain lands>terrace land agriculture>‘slash and burn’ type of shifting agriculture. Moisture and nutrient levels and topography of the lands were found to be major factors responsible for the trend.
24 citations
TL;DR: A survey for the parasitic alga Cephaleuros virescens Kunze in relation to its seasonal distribution in different forest types has been done, finding that healthy leaves contain higher amounts of total nitrogen and total phenol, whereas in algal infected leaves the amounts oftotal sugar, total amino acid and dry weight were higher.
Abstract: A survey for the parasitic alga. Cephaleuros virescens Kunze in relation to its seasonal distribution in different forest types has been done. The alga was absent in gymnosperms and was common in angiosperms. The disease severity was more in summer and the rainy season and absent in winter, Combretum decandrum was found to be most susceptible to this parasite alga. Altogether 49 hosts were recorded out of which 26 were new host records. Healthy leaves contain higher amounts of total nitrogen and total phenol, whereas in algal infected leaves the amounts of total sugar, total amino acid and dry weight were higher.
16 citations
TL;DR: The population response of the two sympatric annual weeds, Galinsoga ciliata (Raf.) Blake and G. parviflora Cav.
Abstract: Summary
The population response of the two sympatric annual weeds, Galinsoga ciliata (Raf.) Blake and G. parviflora Cav., which occur abundantly in croplands and early secondary successional communities in the north-eastern hill region of India was studied in relation to sowing pattern (clump or scattered sowing), population density and soil moisture and texture.
In a given sowing pattern, seed germination of both species declined with increase in sowing density and moisture stress. However, sowing of seeds in clumps and an increased proportion of sand in soil enhanced the germination, Fewer weeds died in the population raised from scattered sowing than from clumped distribution. Plants grown at high moisture level matured earlier, and fertility of the survivors was negatively correlated with both density and moisture stress in both species although G. ciliata was less affected.
Seed output and dry matter yield per pot of both species increased with population density but the increase was not linearly related to the increase in plant numbers, and density-induced reduction in seed output was observed at high densities. Galinsoga ciliata appears to tolerate greater density-stress than G. parviflora. Asubstantial decrease in production of capitula, seeds and dry matter at low moisture level indicates the role played by soil moisture in regulating the population growth of the two weeds. An increased proportion of sand in soil resulted in significantly greater seed production in G. parviflora. Galinsoga ciliata also showed a similar trend although the differences were not statistically significant.
Resume
Equiliber entre les populations de Galinsoga ciliata et G. parviflora. Influence de la technique de semis, de la densite de population et de la texture et de l'humidite du sol
L'etude porte sur les reactions de la population de deux mauvaises herbes annuelles voisines: Galinsoga ciliata et G. parviflora se developpant en abondance dans les endroits cultives et dans les cultures nouvellements implantees sur les collines du Nord Est de l'Inde. Cette etude montre l'influence des techniques de semis (a la volee Ou en poquets) de la densite de population, de l'humidite et de la texture du sol.
Pour une technique de semis donnee, le pourcentage de germination des deux especes diminue avec l'augmentation de la densite de semis et de l'humidite du sol. Cependant le semis en poquets et une texture sableuse du sol favorisent la germination. Dans le cas d'un semis a la volee, on constate une mortalite des plantes plus faibles que dans le cas d'un semis en poquets. Des plantes se developpant dans des conditions tres humides murissent plus vite et leur fertilite est inversement proportionnelle a la densite de populations et au pourcentage d'humidite du sol. Ces observations sont valables pour les deux especes, mais G. ciliata est un peu moins affectee par ces parametres.
La teneur en matiere seche de graines des deux especes augmente avec la densite de population mais cette augmentation n'est pas lineaire en fonction du nombre de plantes et une diminution du nombre de graines par planlcs est observee pour les fortes densites. G. ciliaia semble plus tolerante vis-a-vis de forte densite de populations que G. parviflora. Une diminution notable du nombre des capitules. du nombre de graines et de a l quanlitede maticre seche produite par planted laible nlveau dhumidite, montre ie role jouc par Ihumidile du sol dans la regulation des populations de ces deux adventices. Laugmenlation de l a proportion de sable dans le sol provoque une augmentation significative de la production de graines ehes G. parviflora. Galinsoga ciliata reagit de fagon similaire mais les difTerences ne sont pas statistiquement significatives.
Zusammenfassung
Stctierung de Populationen ion Galinsoga ciliata und G. parviflora. Einflus.s von Saatverfahren. Popidationsdichle. Bodenfeuehte und Bodentextur
Fur die beiden sympatrischen einjahrigen Un-krauter Galinsoga ciliata (Raf.) Blake und Galin-soga parviflora Cav. wurde der Zusammenhang zwisehen der Populationsunderung und dem Saatverfahren (geklumpt oder Breitsaat). der Populationsdichte sowie der Bodenfeuehte und -textur untersueht. Die beiden Arten kommen sehr huufig im Ackerland und im sekundaren Sukzessionsstadium von Ruderalgemeinschaflen i n der nordostliehen Bergregion Indiens vor.
Bei gegebenem Saatverfahren nahm die Kei-mung beider Arten mit Erhohung der Saatsturke und unter Wasserstress ab. Eine geklumpte Saat und ein hohercr Sandanteil im Boden verbesserte die Keimung. Bei der Breitsaat starben weniger Unkruuter ab ais naeh geklumpter Verteilung der Population. Iflanzen. welehe bei hoher Boden-feuehte gewachsen waren. reiften fruher. Ausser-dem war die Fruchtbarkeit der liberlebenden Pflanzen mit der Dichte als auch mit dem Wasser-stress negativ korreliert. Dies traf fur beide Arten zu. 6. ciliaia reagicrte aber weniger cmpfmduch.
Die Samenzahl und der Trockenmasse-Ertrag/Gefass beider Arten erhohte sich mit der Populationsdiehle. aber diese Zunahme stand in keiner linearen Beziehung zur Pflanzenzahl. Bei hohen Dichten wurde eine dlchtebedingte Rcduk-tion der Samenproduktion beobachtet. G. eiliata seheint Dichtestress eher zu tolerieren als G parviflora. Welehe Rolle das Wasser bei der Populationsregulation beider Unkrauter spielt verdeutlicht die reduzierte Bildung von Bluten-standen, Samen und Trockenmasse bei niedrigen Bodenwassergehalten. Ein hoherer Sandanteil im Boden erhohte signifikant die Samenproduktion von G. parviflora. G. cialiata zeigte einen ahn-lichen Trend, die Unterschiede waren aber nicht signifikant.
16 citations
TL;DR: In a sporulated filament, spores which developed first were generally bigger and more resistant to adverse environmental conditions than spores formed later, and the differential loss of viability in spores of a filament may be due to certain intrinsic differences in the physiological/ biochemical properties of the spores.
Abstract: The effects of temperature, desiccation and aging on the viability of spores of Sambhar salt lake blue-green algae, Anabaena fertilissima and Anabaenopsis arnoldii, were studied. Spores of A. arnoldii were found to be more susceptible to temperature variation, desiccation and storage than spores of A. fertilissima. Pre-treatment of spores with higher temperatures, 37° and 47°C, stimulated germination in A. fertilissima. In a sporulated filament, spores which developed first were generally bigger and more resistant to adverse environmental conditions than spores formed later. The differential loss of viability in spores of a filament may be due to certain intrinsic differences in the physiological/ biochemical properties of the spores.
11 citations
TL;DR: In this paper, dry weight loss and chemical changes during the process of decomposition of two types of litters viz., pine (Pinus kesiya Royle) needles and teak (Tectona grandis L.) leaves have been studied in a small freshwater lake using plastic net (1 mm pore size) bags.
Abstract: The dry weight loss and chemical changes during the process of decomposition of two types of litters viz.; pine (Pinus kesiya Royle) needles and teak (Tectona grandis L.) leaves have been studied in a small freshwater lake using plastic net (1 mm pore size) bags. The results reveal that type of litter and depth of water were the most important factors regulating the rate of decomposition. The percentage composition of cellulose and hemicellulose showed little variation and only a minor fall was noted in their values towards the end of the study period. The lignin percentage increased steadily at all the stations except the deepest station. The sugar and amino acid concentration dropped appreciably during the initial phase and stabilised during later periods. The general trend of change in nitrogen percentage was initial fall - increase - fall - stabilisation at a near original value. The rate of decomposition was faster when compared with similar studies in Canada and Europe.
10 citations
8 citations
01 Aug 1983
TL;DR: In this paper, the authors studied the population dynamics and reproductive potential of Imperata cylindrica (L.) Beauv. var. major in successional communities and found that natural regeneration was mainly through tillers which declined sharply in older fallows.
Abstract: Imperata cylindrica (L.) Beauv. var. major is an early successional weed coming up in abandoned fallows after slash and burn agriculture in the north-eastern hill region of India. This study is concerned with the population dynamics and reproductive potential of this species in successional communities. Natural regeneration through seeds occurred only in freshly burnt or cupped fallows though none of the seedlings survived. Natural regeneration was mainly through tillers which declined sharply in older fallows. As a result the species was completely eliminated in fallows older than 5 yrs. This pattern of behaviour of the species has been related to the changing micro-environmental conditions in the developing communities.
TL;DR: In Nostoc linckia, Anabaena variabilis and AnabaENA fertilissima the polyphosphate granules gradually disappear during spore formation and spores become devoid of polyph phosphate on maturation.
TL;DR: Cell differentiation in Anabaena fertilissima and Anabaenopsis arnoldii is accompanied by changes in the lipid composition of akinetes and heterocysts, which may be a reason for diminished photosynthetic acitvity in these cells.
TL;DR: In this article, phenanthrene is converted to 9-hydroxyphenanthrene by acid hexacyanoferrate(III) in 90% aqueous acetic acid.
Abstract: Under kinetically controlled conditions, phenanthrene is converted to 9-hydroxyphenanthrene by acid hexacyanoferrate(III) in 90% aqueous acetic acid. The ϕ value of −4.0 indicates that the reaction proceeds via the formation of a cation radical intermediate.
TL;DR: Iodine is a non-conductor in non-polar solvents, conducts electricity in methanol, ethanol and water as mentioned in this paper, and the majority of the charge carriers in the solutions of charge-transfer complexes of methanoline and ethanol are anion constituents.
TL;DR: Both fungi and bacteria followed almost similar trends of population variation, and the species composition of fungi varied with time.
Abstract: Pinus kesiya Royle needles and Tectona grandis L. leaves were exposed in a freshwater lake at three stations and at different depths for a period of 600 days using plastic net bags (1 mm pore size). The fungal and bacterial populations associated with the two litters were estimated at periodic intervals. Rapid initial colonization (up to 100 days) and a lowering of populations after 200–300 days, followed by another peak after 400–500 days were noted. Both fungi and bacteria followed almost similar trends of population variation. Litter at the shallow stations harboured more fungi and bacteria. The species composition of fungi varied with time. The possible role of terrestrial fungi in aquatic habitats is discussed.
TL;DR: Spore (akinete) differentiation in Anabaena fertilissima in accompanied by changes in the composition of allophycocyanin, phycocianin and phycoerythrin is accompanied by loss of chromophores (bilins) rather than due to the loss of the apoproteins.
01 Mar 1983
TL;DR: In this article, a statistical model analysis has been performed on the θc.m.=180° elastic and inelastic scattering excitation functions in the energy range 27.8≦Ec.
Abstract: A statistical model analysis has been performed on theθc.m.=180° elastic and inelastic scattering excitation functions in the energy range 27.8≦Ec.m.≦31.5 MeV for the12C+28Si system and in the energy range 30.0≦Ec.m.≦32.7 MeV for the16O+28Si system. The exact calculation of the number of effective channels for inelastic excitation gives a value of ~1.5 corresponding to a change of 5° in the angle at which the cross sections are measured. The Hauser-Feshbach cross-sections, when compared to the experimental data, indicate very large (≧90%) direct reaction contributions to the observed cross sections. Good agreement between the theoretical and experimental distributions of the fluctuating cross sections together with the insignificant values of the cross correlation coefficients indicate that the fluctuating component of the experimental cross sections is consistent with the statistical model predictions.
TL;DR: In this article, the authors proposed that the compounds obtained were characterised by analyses, infrared (including far i.r.) and visible spectral studies, magnetic moment and conductivity measurements and many chemical reactions and they have a dimeric structure with a distorted tetrahedral environment around the nickel atom and chloro-bridges.
Abstract: Nitrosyl chloride has been treated with [Ni(PPh3)2X2] (X = Cl, Br, NCS or NO3) to obtain [Ni(PPh3)XCl]2 (X=Cl, Br, NCS or NO3) and [Ni(OPPh3)(SCN)Cl]2. The compounds obtained were characterised by analyses, infrared (including far i.r.) and visible spectral studies, magnetic moment and conductivity measurements and many chemical reactions. It is proposed that the compounds have a dimeric structure with a distorted tetrahedral environment around the nickel atom and chloro-bridges.
TL;DR: Several extra bands in the vicinity of the antisymmetric stretching vibration of the NO 2− ion doped in KI single crystals containing ≈ 10 19 NO 2 − ions per cm 3 have been observed in high resolution infrared studies at 1.7 K as discussed by the authors.
TL;DR: In this paper, it is proposed that the dimeric compounds obtained were characterised by analyses, infrared and visible spectral studies, magnetic moment and conductivity measurements, and they have distorted tetrahedral environment around the nickel atom with chloro-bridging.
Abstract: [Ni(PPh3)2X2] (X = Cl, Br or NO3) on treatment with nitrosyl chloride in a benzene cyclohexane mixture as solvent, gave [Ni(OPPh3)XCl]2 (X = Cl, Br, NO3). Treatment of [Ni(OPPh3)XCl]2, [Ni(PPh3)XCl]2 (X = Cl, Br, SCN, NO3) or [Ni(OPPh3)ICl2] with triphenylphosphine gave [Ni(PPh3)2XCl]. The compounds obtained were characterised by analyses, infrared and visible spectral studies, magnetic moment and conductivity measurements. It is proposed that the dimeric compounds have distorted tetrahedral environment around the nickel atom with chloro-bridging. The compounds, [Ni(PPh3)2XCl] (X = Br, I, or NO3), have tetrahedral structures whereas [Ni(PPh3)2(NCS)Cl] is square-planar.
TL;DR: In this paper, the ESR spectrum of this radical intermediate gave 15 lines and a radical pathway was indicated by ϕ+=−0.50 and kH/kD=6.0.
Abstract: Methoxytoluenes react with acidic K3Fe(CN)6 giving aldehyde as major product. The rate depends on the first powers of the concentrations of substrate, oxidant and acid. A radical pathway is indicated by ϕ+=−0.50 and kH/kD=6.0. The ESR spectrum of this radical intermediate gave 15 lines.
TL;DR: In this paper, the first powers of the concentrations of substrate, oxidant, and alkali were taken into account for naphthol and hexacyanoferrate (III) reactions.
Abstract: The oxidation of naphthols by alkaline hexacyanoferrate(III), at constant ionic strength, gave coupled products. The rate of the reaction was dependent on the first powers of the concentrations of substrate, oxidant, and alkali. The activation energies were 31.8 and 34.5 kJ/mol for α naphthol and β naphthol, respectively. The reaction pathway was via the formation of a radical intermediate, which was detected by electron spin resonance spectroscopy.
TL;DR: In this article, the proton attached to the α-carbon was removed, yielding a radical whose ESR spectrum gave 9 spectral lines, whose activation rate depended on the first powers of the concentrations of substrate and oxidant; the activation parameters were: E=57.0 kJ mol−1.
Abstract: The reaction of trimethylamine with aqueous hexacyanoferrate(III) gave formyldimethylamine. The rate depends on the first powers of the concentrations of substrate and oxidant; the activation parameters were: E=57.0 kJ mol−1, ΔS≠=−154 JK−1 mol−1. The mechanism involves abstraction of the proton attached to the α-carbon, yielding a radical, whose ESR spectrum gave 9 spectral lines.
TL;DR: In this article, the reaction of pyrogallol with alkaline hexacyanoferrate (III) at constant ionic strength gave 3,3′,5,5′-tetrahydroxy-4,4′-diphenoquinone in a yield of 80%.
Abstract: The reaction of pyrogallol with alkaline hexacyanoferrate(III) at constant ionic strength gave 3,3′,5,5′-tetrahydroxy-4,4′-diphenoquinone in a yield of 80%. The rate is dependent on the first powers of the concentrations of substrate, oxidant and alkali. The reaction pathway could be visualized as proceeding via a radical intermediate formed in the rate determining step. This radical was detected by ESR spectroscopy as two triplets with the intensity ratios of (1,2,1), (1,2,1), and showed absorptions at 655 nm, and at 1560 cm−1 in the infrared region.
DOI•
01 Apr 1983TL;DR: In this paper, the interaction between weak interacting systems such as benzene, CCl4-cyclohexane, toluene and xylene has been studied and the equilibrium constants and other thermodynamic parameters have been reported.
Abstract: Viscometric method has been used to study the interaction between the weak interacting systems such as benzene-CCl4-cyclohexane, toluene-CCl4-cyclohexane ando- xylene-CCl4-cyclohexane. The equilibrium constants and other thermodynamic parameters have been reported and compared with literature data.
TL;DR: A new compound of nickel(III), [Ni(OPPh 3 )Cl 2 I] has been prepared by the action of nitrosyl chloride or chlorine gas on [NiPPh 3 ] 2 I 2 ] as discussed by the authors.
TL;DR: In this paper, the existence of a second-order phase transition associated with spontaneous supersymmetry breaking in a prototype globally supersymmetric model with a conserved fermion number is demonstrated.
Abstract: The existence of a second-order phase transition associated with spontaneous supersymmetry breaking in a prototype globally supersymmetric model with a conserved fermion number is demonstrated. The model is solved exactly and it is shown that one of the superfields develops a vacuum expectation value below a critical temperature and that the ground-state energy is nonzero.
TL;DR: In this article, the rate of the displacement of the atylacetonate ligand from the Mn(acac)3 complex has been studied in methanol, in the presence of perchloric acid.
Abstract: The rate of the displacement of the aœtylacetonate ligand from the Mn(acac)3 complex has been studied in methanol, in the presence of perchloric acid. Ion pair formation has been suggested. Mn(II) ions have been found to retard the rate of ligand displacement that has been attributed to the formation of a mixed valence complex.