Showing papers by "Jawaharlal Nehru University published in 1993"

Competition and allelopathy in aquatic plant communities

Abstract: The paper reviews the published literature on the studies of competition and allelopathy in aquatic plant communities. Taking a broader view of the community, the studies on interactions between macrophytes and microphytes, macrophytes and macro-invertebrates and microbial communities are also reviewed. The role of these interactions in the structure and dynamics of aquatic communities has been discussed in light of the current hypotheses concerning competition in terrestrial communities. The available information suggests that the aquatic plants of various growth forms differ greatly among themselves in their responses and adaptations to competition and allelopathy. The possible application of these interactions in biological control of plant pests and in agriculture is also summarized. We conclude that the observed differences in these interactions between the terrestrial and aquatic environment are due to the effects of water as a non-resource variable as well as due to special adaptive characteristics of aquatic plants. Further we hypothesize that the aquatic plants adopt both competitive and allelopathic strategies under different conditions and in interactions with different plants. The review highlights that our knowledge of both competition and allelopathy among aquatic plant communities is inadequate and fragmentary, and therefore, both extensive and intensive studies are required.

Changes in the Activities of Anti-Oxidant Enzymes during Exposure of Intact Wheat Leaves to Strong Visible Light at Different Temperatures in the Presence of Protein Synthesis Inhibitors.

Abstract: Changes in activities of the enzymes involved in the metabolism of active oxygen species were followed in homogenates prepared from wheat leaves (Triticum aestivum L.) exposed to strong visible light (600 W m-2). The activities of superoxide dismutase (SOD), ascorbate peroxidase, and monodehydroascorbate reductase increased significantly on prolonged illumination of the leaves, indicating an increase in the rate of generation of active oxygen species. This increase was further exacerbated when high light stress was combined with low temperature (8[deg]C). Our results indicate that the increase in activities of SOD and ascorbate peroxidase involved de novo protein synthesis that was sensitive to the nuclear-directed protein synthesis inhibitor cycloheximide. The activity of catalase, on the other hand, decreased on exposure to strong light, which could be due to its photolability, particularly at lower temperatures. Ascorbate and total carotenoid contents also increased on light treatment of the leaves. The induction of the enzymes except for catalase and increase in the levels of ascorbate and total carotenoids in response to the stress conditions indicate that they play an important role in the protection of higher plants from the damaging effects of toxic active species.

Proline in relation to free radical production in seedlings of Brassica juncea raised under sodium chloride stress

Abstract: The production of malondialdehyde (MDA) was higher in cotyledons from NaCl-raised Brassica juncea seedlings than in control seedlings. Light accelerated the MDA-producing capacity of thylakoids isolated from both control and treated seedlings. When exposed to strong white light (920 μmol photons m-2 s-1) the thylakoids from NaCl seedlings produced nearly 5 times more MDA than control thylakoids. In the cotyledons of NaCl seedlings, the proline level was 24-fold higher than in controls. The presence of proline during exposure of thylakoids to white light decreased MDA levels. The reduction in MDA production was higher in the thylakoids of NaCl seedlings than of controls. It is proposed that proline accumulation has an adaptive significance as it lowers the generation of free radicals and thus reduces the lipid peroxidation linked membrane deterioration under stress.

Agrarian change and occupational diversification: Non‐agricultural employment and rural development in West Bengal

Abstract: Based on evidence from the quinquennial surveys on employment by the National Sample Survey Organisation, it has been argued that, as part of the process of change associated with the Green Revolution, rural India is witnessing an agricultural growth‐induced diversification in economic activity in favour of non‐agricultural actvities. This article examines that argument using evidence relating to India as a whole and the state of West Bengal in particular. The analysis suggests that the observed occupational diversification in rural India over the last decade‐and‐a‐half is not so much a fall‐out of rural dynamism in the wake of the Green Revolution, but a reflection of the fact that two‐and‐a‐half decades after the Green Revolution began in India, much of the country is yet to experience the impact of that process.

Effect of rapid eye movement sleep deprivation on rat brain Na‐K ATPase activity

Abstract: Since rapid eye movement (REM) sleep deprivation has been reported to affect the neuronal excitability in the brain, it was hypothesized that a change in the neuronal membrane-bound Na-K ATPase activity might be at least one of the factors inducing such a change. Therefore, in this study rats were deprived of REM sleep by using the platform technique and enzyme activity was estimated in the whole brain, in different regions of the brain and in microsomal preparations. Deprivation was carried out for varying periods and suitable control experiments were conducted to rule out the possibility of nonspecific effects. The observation supported our hypothesis and showed primarily that the deprivation increased the enzyme activity in the rat brain. It showed also that the pons and the medulla were the first sites to be affected by deprivation. The probable mechanism producing such a change is discussed.

The glyoxalase system in higher plants: regulation in growth and differentiation.

Abstract: 39. Hall, J. C. and Vander Jagt, D. I,. (1979) Anal. Hiochem. 98,472-477 Oray, B. and Norton, S. J. (1980) Hiochim. Biophys. Acta611, 168-173 I’rincipato, G. H., Kosi, G., Talesa, V., Hocchini, V. and Giovannini, E. (1984) Biochem. Int. 9, 351-359 I’rincipato, G. H., Rosi, G., Talesa, V. and Giovannini, E. (1985) IKCS Med. Sci. 13,952-953 Murata, K., Inoue, Y., Watanabe. K., Fukuda, Y., Saikusa, T., Shimosaka, M. and Kimura, A. (1986) Agric. Biol. Chem. 50, 135-142 Norton, S. J., Principato, G. B., Talesa, V., Lupattelli, M. and Kosi, G. ( 1989) Enzyme 42, 189196 Ball, J. C. and Vander Jagt, L). I,. (1981) Hiochemistry

Transport and distribution of heavy metals in Cauvery river

Abstract: Heavy metal transport in Cauvery river chiefly takes place in the particulate form. Tributaries Hemevathi and Kabini draining highly mineralized areas contribute significantly to the heavy metal load of the Cauvery river. Particulate metal transport is influenced by the presence of major dams built across the river. Factor analysis of the elemental data identifies two major group of heavy metals, (a) Fe, Mn, Cr, V and Ti and (b) Cu, Pb and Zn in the suspended sediments of Cauvery river. Heavy metals in surface sediments show wide variations in their concentrations due to the non-uniform grain size distribution of the sediments. The elements Fe, Mn, Pb, Cu, Zn, Ni, Co and As are dominantly present in the <20 μm fraction of the river sediments. Speciation studies show that Fe-Mn oxide phase held the largest share of heavy metals in the sediments. The depth variation of heavy metals in the core sediments suggest their similar mobility during diagenesis. Geoaccumulation indices calculated suggest that Cd, Zn, Cr, Pb, Cu and Ni are enriched in sediments several times over background values.

Heavy metals distribution and fractionation in sediments of the Mahanadi River basin, India

Abstract: Heavy metals distribution in core sediments, different size fractions of bed sediments (>212 urn, 90-212 jam, 63–90 urn, 53–63 urn, 30 urn, 20–30 μm, 10–20 urn, 2–10 urn, <2 μm) have been discussed. Pb, Zn, and Cr have been accumulating in recent years in the sediments. Si, Al, Fe, Ca, and Mg dominate the bed and suspended sediment composition. Metals show increasing concentrations in finer sediments. Applying multivariate analysis to sediment composition, metals have been grouped into different factors depending upon their source of origin. Chemical fractionation studies on suspended and bed sediments show Fe, Zn, Cu, and Pb are associated with the residual fraction and Mn with the exchangeable fraction.

Geochemistry of the Cauvery Estuary, East Coast of India

Abstract: Major ion chemistry of water and elemental geochemistry of suspended and surficial sediments collected from the Cauvery Estuary were studied to understand the geochemical processes in this tropical estuarine system. Specific conductance (EC), total dissolved solids (TDS), and total suspended matter (TSM) increased conservatively with increasing chlorinity. In general, SO4 2−, Na, K, Ca, and Mg showed an increasing trend while H4SiO4 and PO4 3− showed a decreasing trend toward the sea. Additional removal mechanisms operating for these ions in the Cauvery Estuary have been identified based on observed concentrations. Factor analysis pointed out the sources contributing to the observed trends in estuarine water chemistry. POC and PON decreased toward the high chlorinity zone. TSM in the Cauvery Estuary were mostly of inorganic nature. Stable carbon isotope values showed that the carbon was equally of marine and terrestrial origin and helped to delineate the contribution of river water and seawater. The ϕ mean size (a logarithmic grain size scale commonly used by sedimentologists) indicated that the surficial sediments were primarily comprised of coarse and silt, whereas suspended sediments were principally silt and clay. Suspended sediments were enriched in clays compared to surficial sediments. Quartz and feldspar were abundant among detritals while chlorite, kaolinite, and montmorillonite were dominant among clays. Silicon was the most abundant element in the sediments followed by Al, Ca, Na, K, Fe, Mn, and P. Heavy metals were enriched in the suspended sediments compared to the surficial bottom sediments as follows: Fe = 3.5, Mn = 7.4, Pb = 1.1, Zn = 15.2, Cu = 7.4, and Cr = 4.0. The levels of Cd, Cr, Zn, and Fe increased up the middle reaches and then decreased toward the sea due to urban effluent and fertilizer input. Size fractionation studies indicated that the metal concentration in the finer fraction was 50% higher by mass than the coarse silt and fine silt fractions. Chemical fractionation studies showed that the abundance of metals were in the order of residual > organic/sulfide > carbonate > Fe/Mn oxide > exchangeable fractions.

Liquid–liquid transition in polymers and glass‐forming liquids

Abstract: It is shown that many simple glass-forming liquids exhibit a phenomenon known in the area of polymer science as the liquid–liquid transition. The phenomenon manifests itself as a third-order transition in the equilibrium liquid-specific heat data around approximately 1.2 Tg and also as a bifurcation of the liquid relaxation into primary and secondry processes. It is stressed that the above phenomenon is due to a smooth changeover of the liquid from one dynamic regime to the other and hence is not due to any real phase transition. It is suggested that a liquid cluster kind of picture for the supercooled liquid regime, is capable of explaining the above phenomenon and is consistent with observation made on polymers and monomeric liquids. © 1993 John Wiley & Sons, Inc.

Germinable soil seed bank dynamics during the gap phase of a humid tropical forest in the Western Ghats of Kerala, India

Abstract: The present study showed that the density of germinable seeds in the soil of a humid tropical forest ecosystem at Nelliampathy, in the Western Ghats of Kerala in India, fluctuates sharply at different times of the year. There were more germinable seeds in the soil during the monsoon season. Regeneration was activated after canopy gap formation and thus a decline in the soil seed density in 1-year-old gaps was recorded. However, soil seed density increased with gap age. Differences were found between primary, late secondary and early secondary categories of species with respect to their soil seed bank. There were more seeds of primary species in the soil of natural gaps than in selection felled ones, while the seeds of early secondary shrubs and herbs were more in the soil of selection felled gaps than in natural gaps. The soil seed banks of the primary forest species, being transient, are not an important conservation tool for these species.

Leaf Senescence-induced Alterations in Structure and Function of Higher Plant Chloroplasts

Abstract: Leaf senescence constitutes a crucial aspect of plant life. In this chapter, we highlight various possible reactions involved in the decline of photochemical activity of chloroplasts during leaf senescence. Loss of photosynthetic pigments is the most conspicuous event during this phase. Electron transport activities catalysed by photosystem n and photosystem I (PS II and PS I) also decline during senescence. The progress of senescence appears to affect not only the oxygen-evolving complex but also the QA ⇄ QB site of PS II and cytochrome b 6 lf complex in the electron transport chain. As a combined result of all these perturbations. an imbalance between PS II and PS I catalysed activities is induced. which eventually limits photosynthesis in senescing leaves. The studies on molecular aspects of leaf senescence focus on identification of specific changes in gene expression associated with the onset and progress of senescence phase. A critical review of the current state of knowledge pertaining to senescence-induced changes in thylakoid structure and functional capacities of the photosynthetic membranes is presented. It points to specific directions for future investigation to get a better understanding of the mechanism(s) involved in regulation energy transfer and energy conservation in the senescing chloroplasts.

Conservation and Management of Rivers in India: Case-study of the River Yamuna

Abstract: The River Yamuna, originating in the Himalayas, is the largest tributary of the River Ganga (Ganges) into which it flows at Allahabad. Its drainage basin covers about 42% of the Ganga River basin and about 11% of India's total land area. The area of the Yamuna drainage basin is densely populated and under intensive agriculture, while industrial activity is also rapidly growing in it. Climatically, a large part of the basin is semi-arid, and the river-flow depends upon highly erratic monsoonal rains. Therefore, the River and its tributaries have been regulated for over a century by dams and barrages for domestic water-supply and irrigation.Besides increased flow-regulation, the River's system has been under increasing anthropogenic stress from discharge of—mostly untreated—domestic and industrial wastewaters, and from other activities in the basin. River Yamuna is severely polluted by domestic and industrial effluents especially from Delhi down to Agra. Water extraction and consequently low flow has affected the selfpurification capacity of the River. The greater inflow of River Chambal helps River Yamuna to recover to some extent after their confluence near Etawah.Studies of water quality and biota of the River Yamuna along its course during the past 30 years show rapid deterioration of water-quality, loss of fisheries, and significant changes in the biotic communities. In the manner of River Yamuna, its tributaries have also become increasingly polluted during the same period. There has, however, been little attention paid to the management of the River system and conservation of its resources, except for some efforts at the treatment of sewage effluents but emphasizing only water-quality. Ignoring the river-flood-plain interactions which play significant roles in the ecology of a river, most of the floodplain has been reclaimed by constructing high levees.We emphasize that the Yamuna River basin should be treated as one ecocomplex in developing appropriate management strategies, and that the conservation of waterquality and biota can be achieved through protection and better management of floodplains than has been practised to date.

Rapid eye movement sleep deprivation induced changes in glucose metabolic enzymes in rat brain

Abstract: Glucose metabolism and energy expenditure are altered during rapid eye movement (REM) sleep. To understand this mechanism, it was hypothesized that the enzymes involved in the metabolism of glucose, viz. hexokinase and glucose-6-phosphatase, are affected by REM sleep deprivation. The flower pot technique was used for 1-, 2- and 4-day periods of REM sleep deprivation. Suitable control experiments were carried out to rule out the nonspecific effects. The results showed that glucose-6-phosphatase was first to be affected, and it showed decreased activity. In longer periods of deprivation, there was an increase in hexokinase activity. Both the altered enzyme activities returned to baseline level on recovery from REM sleep deprivation. Control experiments suggest that alterations were primarily caused by REM sleep deprivation, not nonspecific effects.

Effect of Radiation on Glyoxalase I and Glyoxalase II Activities in Spleen and Liver of Mice

Abstract: Swiss albino mice (7-8 weeks old) were irradiated with different doses (0-25 Gy) of gamma-radiation at a dose-rate of 0.05 Gy/s. The specific activities of glyoxalase I (GI) and glyoxalase II (GII) were determined in the spleen and liver immediately and on the 3rd and 6th day postirradiation. The results indicate that the glyoxalase system is radiosensitive, particularly glyoxalase I whose activity was enhanced even at low doses (0.5 Gy). The magnitude and mode of the radiation effect depends on dose and tissue. The patterns of the GI/GII ratio in the liver and spleen was very similar when measured immediately after irradiation. The radiation effect on the glyoxalase system persists even in the postirradiation period and was inversely related to the dose-rate. GSH and caffeine increased and chlorpromazine decreased the radiation-induced activity of GI, but all three modifiers enhanced radiation-induced inactivation of GII. Since the glyoxalase system may play an important role in the regulation of cell division and differentiation, radiation effects on this system may have some biochemical consequences.

Sediment transfer in the glaciofluvial environment — a Himalayan perspective

Abstract: The Alaknanda river, a major Himalayan proglacial stream, and its tributaries have been studied to evaluate sediment sources, production mechanisms, and transport pathways in the Alaknanda river basin. The study is based on a single-time sampling of the river and its tributaries and gives an insight into the suspended load pattern of the river from its source to its confluence with the other major Himalayan proglacial stream, the Bhagirathi. It is tentatively concluded that the suspended load of the Alaknanda is primarily due to natural processes and events and does not reflect the effects of human intervention.

Involvement of active oxygen species in photoinhibition of photosystem. II: Protection of photosynthetic efficiency and inhibition of lipid peroxidation by superoxide dismutase and catalase

Abstract: Superoxide dismutase and catalase were observed to prevent the loss of photosynthetic electron transport activity and the variable chlorophyll fluorescence in wheat photosystem II (PSII) preparations exposed to strong visible light at 25 and 5 °C. A simultaneous increase in the rate of lipid peroxidation in PSII membranes was also observed which was significantly inhibited in the presence of superoxide dismutase and catalase. Our results strongly suggest the generation of active species such as O 2 − , H 2 O 2 and OH · in the PSII complex during photoinhibition at ambient temperature and low temperatures. The protection of PSII functions against strong-light-induced damage by the antioxidant enzymes was, however, not complete, which might suggest the existence of an oxygen-independent mechanism operating simultaneously.