Prasanna Mohanty's research while affiliated with Regional Plant Resource Centre and other places
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Publications (115)
Two-week-old pea (Pisum sativum var. Arkal) plants were subjected to elevated temperature (38 degrees C/42 degrees C) in dark for 14-15 h. The effect of heat treatment on light-induced phosphorylation of LHCII and LHCII migration in the thylakoid membranes were investigated. The heat treatment did cause a substantial (more than two fold) increase i...
When Spirulina platensis filaments were exposed to 0.75 mW.m-2.s-1 of ultraviolet-B radiation (the ultraviolet-B radiation under clear sky condition is ~1.0 mW.m-2.s-1), an inhibition in photosystem II activity was observed, the inhibition being 90% after 90 min exposure. Upon exposure to ultraviolet-B, the room temperature emission characteristics...
It has been demonstrated that cyclic polyether, K-picrate-18-crown-6 inhibited photosynthetic electron transport (Sabat et al., 1991, Z. Naturforsch. 46c, 87-92). We further analyzed the alterations induced in the fast chlorophyll α fluorescence and thermoluminescence pattern of pea thylakoids by calcium-18-crown-6 (crown-picrate). The results indi...
Inhibitory effects of lanthanum-crown [La-(Pic)3 (15-crown-6) 3H2O] was investigated on the O2 evolution activity of photosystem II particles. Lanthanum (La)-crown inhibited the electron flow at the reducing side of PS II complex. Short duration (1-2 min) treatment of PS II membranes with trypsin partly developed resistance to La-crown inhibition....
Thylakoids isolated from SAN 9785 (4-chloro-5-dimethylamino-2-phenyl-3(2H)-pyridazi-none)-treated pea plants showed an inhibition of “state transition” and the light-harvesting complex II (LHC II) phosphorylation-mediated changes in the energy distribution between photosystem II (PS II) and photosystem I (PS I) as measured by a decrease in PS II an...
Chloroplast structure and function is known to alter during foliar senescence. Besides, the alterations in the structural organisation of thylakoid membranes changes in the steady state levels of thylakoid membrane proteins occur due to leaf ageing. We monitored temporal changes in some of the specific proteins of thylakoid membrane protein complex...
Spirulina platensis trichomes grown in Zarrouks medium having total Na+ concentration as 0.14 M when transferred to fresh Zarrouks medium containing enhanced level of Na+ ions equal to 0.86 M showed 30% more accumulation of Na+ intracellularly as compared to the control. An inhibition of photosystem II activity to almost 66% was observed. Also due...
Two-month-old seedlings of Bruguiera parvifora were treated with varying levels of NaCl (100, 200 and 400 mM) under hydroponic culture. Total proteins were extracted from leaves of control and NaCl treated plants after 7, 14, 30 and 45 d of treatment and analysed by SDS-PAGE. As visualized from SDS-PAGE, the intensity of several protein bands of mo...
The effect of K-picrate-18-crown-6 (crown) on the photoelectron transport activity of beet spinach thylakoid membranes was investigated. Addition of micromolar concentration of crown to thylakoid preparation inhibited p-benzoquinone, chloride-indophenol, methyl viologen supported Hill activities maximally by 75 per cent in a concentration dependent...
The redox state of plastoquinone (PQ) pool is the incipient signal in the signal transduction pathway of state transition mechanism, shifting from state I to state II and vice versa. The redox state of the QA, the primary acceptor of photosystem II (PSII) and the PQ pool are easily monitored by the OJIP fast fluorescence transients. The OJIP fast C...
We investigated the role of a cold-inducible and redox-regulated RNA helicase, CrhR, in the energy redistribution and adjustment of stoichiometry between photosystem I (PSI) and photosystem II (PSII), at low temperature in Synechocystis sp. PCC 6803. The results suggest that during low temperature incubation, i.e., when cells are shifted from 34°C...
The effect of temperature on the photosynthetic machinery is crucial for the fundamental understanding of plant physiology and the bioengineering of heat-tolerant varieties. In our study, Arabidopsis thaliana was exposed to mild (40°C), short-term heat stress in the dark to evaluate the heat-triggered phosphorylation and migration of light harvesti...
Fusarium induced-stress-protein (FISP) of ∼51 kDa molecular mass was detected in seven day old germinated wheat (Triticum aestivum var Sonalika) seedlings infected with F. oxysporum for a period of seven days. This particular stress protein (FISP) of ∼51 kDa was over-expressed in the case of Fusarium infected seedlings compared to the untreated see...
One-year-old seedlings of Bruguiera gymnorrhiza (L) Savingay were exposed to 500 mM NaCl for 6d under hydroponic culture condition to characterize the changes in leaf and thylakoid protein profiles in response to short-term salt exposures. Significant changes in leaf dry mass, chlorophylls and soluble leaf proteins were observed in short term of sa...
Intact and metabolically very active mesophyll protoplasts were isolated rapidly from pea (Pisum sativum) leaves. The functional performance of protoplasts at various stages of their isolation was analyzed by using fast Chl αfluorescence OJIP transients and compared with that of intact leaves. The results demonstrated that the OJIP transients could...
A significant decrease in the amount of a protein, whose migration in two-dimensional gel electrophoresis corresponds to an apparent molecular mass of 23 kDa and pI = 6.5, was observed in leaves of NaCl-treated Bruguiera parviflora (Roxb.) Wt. & Arn. ex Griff. seedlings. This particular salt-sensitive protein, designated as SSP-23, almost disappear...
Photosynthesis research in India can be traced back several thousand years, with the mention of the Sun energizing the plants, which form food for all living creatures on the earth (from the Mahabharata, the great epic, ca. 2600 B.C.) and the report of Sage Parasara (ca. 100 B.C.) on the ability of plants to make their own food, due to their pigmen...
Exposure of healthy wheat seeds (Triticum aestivum var Sonalika) to mild dose of cadmium (Cd(2+)) given as 50 microM CdCl(2) for 48 h and then washed off Cd(2+) offered resistance to the subsequent infection by Fusarium oxysporum inoculum. Seven days old seedlings having two primary leaves were aseptically inoculated with fungus, F. oxysporum (1 x...
Aluminum toxicity in acidic soils poses a major threat to plant growth and development. The effects of a low dose of aluminum (50 microM, AlCl3) on various cytological parameters, including mitotic and meiotic chromosomal divisions, in situ nuclear DNA content, interphase nuclear volume (INV), and pollen fertility were compared in untreated (contro...
Salt induced biochemical changes were studied in hydroponically grown plants of a salt secrector mangrove, Aegiceras corniculatum (Myrsinaceae). Total Chl content decreased in 250 mM NaCl over the 30 d treatment period. The Chl a:b ratio remained unchanged in leaves, but carotenoids showed a 1.6-fold decrease. Total sugar content decreased to half...
In order to assess the role of the antioxidative defense system against salt treatment, the activities of some antioxidative enzymes and levels of antioxidants were monitored in a true mangrove, Bruguiera parviflora, subjected to varying levels of NaCl under hydroponic culture. In the leaves of B. parviflora, salt treatment preferentially enhanced...
Two-month-old healthy seedlings of a true mangrove, Bruguiera parviflora, raised from propagules in normal nursery conditions were subjected to varying concentrations of NaCl for 45 d under hydroponic
culture conditions to investigate the defence potentials of antioxidative enzymes against NaCl stress imposed oxidative stress.
Changes in the activi...
Senescence-induced alterations in photosystem II (PS II) structure and photofunctions were probed in cucumber (Cucumis sativus) cotyledons, using fast O-J-I-P Chlorophyll a (Chl a) fluorescence transients. Analysis of measured and derived parameters of the fast fluorescence O-J-I-P transient revealed senescence-induced alterations in (i), PS II acc...
Structure and function of chloroplasts are known to after during senescence. The senescence-induced specific changes in light harvesting antenna of photosystem II (PSII) and photosystem I (PSI) were investigated in Cucumis cotyledons. Purified light harvesting complex II (LHCII) and photosystem I complex were isolated from 6-day non-senescing and 2...
Photosynthesis research in India can be traced back several thousand years, with the mention of the Sun energizing the plants, which form food for all living creatures on the earth (from the Mahabharata, the great epic, ca. 2600 B.C.) and the report of Sage Parasara (ca. 100 B.C.) on the ability of plants to make their own food, due to their pigmen...
Less than 5% of the total pool of free amino acids in plants under stress-free conditions is p rovided by proline. In many plants under various forms of stress, the concentration increases up to 80% of the amino acid pool. This observation raises the question about the molecular mechanisms, making a high proline concentration favourable under stres...
Enhancement in the rates of photosystem (PS) II-catalysed O2 evolution was observed with thylakoids isolated from cotyledonary leaves of Brassica juncea seedlings raised in medium containing 200 mM NaCl compared to controls. The nature of this enhancement in PS II activity by NaCl treatment has been investigated. The pH profile showed an optimal PS...
Exposure of isolated thylakoids or intact plants to elevated temperature is known to inhibit photosynthesis at multiple sites. We have investigated the effect of elevated temperature (40 degrees C) for 24 hr in dark on rice seedlings to characterize the extent of damage by in vivo heat stress on photofunctions of photosystem II (PSII). Chl a fluore...
Exposure of 25 °C-grown, seven-day-old rice seedlings to mild heat stress of 40 °C for 24 h in dark did not cause any change in protein or pigment content of the thylakoids, but produced major disorganization of chloroplast ultrastructure. This heat induced disorganization of thylakoid structure/organization caused significant (∼65 percnt;) loss in...
Molecular oxygen in electronic singlet state is a very powerful oxidant. Its damaging action in a variety of biological processes has been well recognized. Here we report the singlet oxygen quenching action of proline. Singlet oxygen (1O2) was produced photochemically by irradiating a solution of sensitiser and detected by following the formation o...
We report the formation and appearance of loosely stacked extended grana like structures along with plastoglobuli in the chloroplasts isolated from 27-day old senescing cucumber cotyledons. The origin and the nature of these extended grana structures have not been elucidated earlier. We isolated Photosystem I complexes from 6-day-old control and 27...
Phycobilisomes (Pbsomes) are the supra macromolecular pigment protein complexes of cyanobacteria. Synechococcus Pbsomes are comprised of phycocyanins (PC) and allophycocyanins (APC). Pbsomes are major light harvesting antennae and also absorb ultraviolet-B (UV-B) radiation (280-320 nm). Synechococcus Pbsomes, upon exposure to low dose of UV-B (0.28...
After a 6 min exposure of isolated thylakoids to 43 C, the extent of phosphorylation of light-harvesting complex of photosystem 2 (LHC2) was higher than in control thylakoids kept at 25 C. Similarly, the exposure of intact spinach plants to 43 C in dark for 11 h induced higher extent of thylakoid LHC2 phosphorylation than in control plants kept at...
Incubation of Spirulina platensis at enhanced Na+ concentrations resulted in 30% increased intracellular accumulation of Na+ ions. This accumulation of Na+ ions intracellularly altered the phycobilisome organization as revealed by transmission electron microscopic data and changes
in the absorption spectrum. The room temperature emission peak at 63...
Intact trichomes of Spirulina platensis are exposed to ultraviolet- B (UV-B) radiation (270-320 nm; 1.9 mW m(-2)) for 9 h. This UV-B exposure results in alterations in the pigment-protein complexes and in the fluorescence emission profile of the chlorophyll-protein complexes of the thylakoids as compared with thylakoids isolated from control dark-a...
Effect of UV-B (1.9 W m-2) alone or in combination with supplemental "white light". WL (20 W m-2) exposure was studied on the energy transfer process of intact phycobilisomes isolated from Spirulina platensis. Exposure of UV-B or supplemental irradiation induced a decrease in room temperature fluorescence intensity and caused a
shift towards shorte...
We studied the development of chloroplasts from etioplasts in the cotyledonary leaves of 4-d-old dark-grown cucumber (Cucumis
sativus) seedlings after irradiation (20 μmol m-2 s-1). Upon irradiation, the triggering of chlorophyll (Chl) synthesis and accumulation showed a relatively short lag phase. The
irradiation of etiolated seedlings initiated t...
Senescence induced temporal changes in photosystems can be conveniently studied in cotyledonary leaves. We monitored the protein, chlorophyll and electron transport activities in Cucumis sativus cv Poinsette cotyledonary leaves and observed that by 20th day, there was a 50%, 41% and 30-33% decline in the chlorophyll, protein and photosystem II acti...
PS II is a multicomponent thylakoid membrane protein complex which converts solar radiation into chemical potential. PS II enriched membrane preparations lose their oxygen evolution activity upon thermal denaturation of their associated proteins. PS II enriched membranes were prepared from beet spinach (Beta vulgaris palanga) leaves, and 6 day and...
For tropical agriculture, elevated temperature stress is one of the most important environmental stresses. The photosynthetic apparatus is extremely sensitive to heat stress. In this chapter the nature of heat induced damage and the alterations in the structure and functions of photosystems by temperature stress are discussed and the relative sensi...
Exposure of ultraviolet-B (280-320 nm, 1.9 mW m-2 s-1) radiation of intact Spirulina platensis for 9 h caused specific loss of the 85.5 KDa anchor protein of phycobilisomes, the major light-harvesting antenna complex of photosystem II. Associated with the loss of 85.5 KDa protein, the UV-B irradiation also caused photobleaching of phycobilins and a...
Carotenoids are widespread in living organisms. All the photosynthetic organisms contain carotenoids in their thylakoid membranes performing important role in the photochemical functions. Some green algae produce large amounts of carotenoids which accumulate outside the thylakoids and are known as secondary carotenoids. Two such organisms which hav...
Phycobilisomes (PBS), the major light harvesting antenna of the cyanobacterium Synechococcus contain phycocyanin (PC) and allophycocyanin (APC) as major pigment-protein complexes. PBS also absorb ultraviolet-B (280-320 nm) radiation. Exposure of Synechococcus PBS to low dose of UV-B (approximately 0.28 mw.cm-2) for 90 min induced change in absorpti...
Phycobilisomes (PBS), the major light harvesting antenna of the cyanobacterium Synechococcus contain phycocyanin (PC) and allophycocyanin (APC) as major pigment-protein complexes. PBS also absorb ultraviolet-B (280-320 nm) radiation. Exposure of Synechococcus PBS to low dose of UV-B (∼0.28 mw.cm-2) for 90 min induced change in absorption, emission...
Cotyledonary leaves of Cucumis sativus cv. Poinsette exhibited senescence-induced losses in chlorophyll (Chl) and protein contents within three weeks since germination. Chl and protein concentrations in cotyledonary leaves approached maximum on 6th d after germination and they declined to 50 and 41 %, respectively, by the 20th day of growth. Activi...
Our goal is to find a practical way to characterize rice plants in respect to their behavior upon different heat treatments. Screening of cultivars is planed (1). This way we hope to be able to improve the selection of seeds for a certain agricultural area and to improve the prediction of crop yield of cultures under heat stress by fast fluorescenc...
Ultraviolet (UV)B irradiation which rises on the earth’s surface due to depletion of ozone layer (1), affects the photosynthetic process at multiple sites (2). Several workers have studied the effects of UV-B radiation on structure and function of photosystems in cyanobacteria (3). The cyanobacterial thylakoids possess two distict pigment protein c...
Heat treatment (HT) of leaves, isolated chloroplasts or intact plants, causes inhibition of electron transport activities of both PSII and PSI (1). The order of thermal sensitivity of various photosynthetic light reactions is oxygen evolution, photochemical activity of PSII, Photophosphorylation, Cyt b6/f complex and photochemical activity of PSI (...
We have investigated the inhibitory effect of K-crown (18-crown-6 potassium picrate) on photosystem II (PSII)-enriched membrane fragments and O2-evolving core complexes. K-crown at 2-4 microM inhibits about half the control level of O2-evolution activity in both types of PSII samples. Oxygen-evolution studies demonstrated that the ether works by in...
Investigations were carried out to determine the involvement of proline in protecting thylakoid membranes against photodamage. The exposure of thylakoids isolated from the cotyledons of Brassica juncea to photoinhibitory light caused a linear increase in lipid peroxidation with time as measured by the assay of conjugated dienes and malondialdehyde...
The kinetic parameters of different sites of electron donation to photosystem I (PS I) were evaluated in Spirulina platensis thylakoids. Reduced 2,6-dichlorophenolindophenol (DCIPH2) exhibited two sites of electron donation, with apparent K(m) values of 8 and 40 microM each. The corresponding value for reduced N-tetramethyl-p-phenylenediamine (TMPD...
The after-effects of 24 h high temperature (35 or 45 °C) treatment on the photochemical activities and photooxidative lipid
peroxidation, subsequent to their irradiation were studied in 7-d-old etiolated rice (Oryza sativa) seedlings. Photosystem (PS) 1 and PS 2 mediated photoreactions of thylakoids isolated from the seedlings exposed to high
tempe...
Effect of low and high doses (0.25, 0.5 and 0.75 mW cm-2 s-1) of UV-B (maximal emission at 300 nm) exposure was investigated on absorption and emission characteristics of intact phycobilisomes (PBsomes) isolated from cyanobacterium Synechococcus. It was observed that exposure to low intensity of UV-B caused a time dependent bleaching of red absorpt...
Glow curves from spinach leaf discs infiltrated with o-phthalaldehyde (OPA) show significant similarity to those obtained by DCMU treatment which is known to block the electron flow from QA, the stable acceptor of Photosystem II (PS II). In both the cases, the thermoluminescence (TL) peak II (Q band) was intensified significantly, whereas peaks III...
Twenty polystyrene-g-gelatin samples were synthesised using Ce(IV) as the free radical initiator in order to make biodegradable polystyrene. Recovery of polystyrene from acid hydrolysis of the grafted sample and the appearance of new bands of gelatin at 3479 cm−1, 3235 cm−1, 1060 cm−1 and 1370 cm−1 in the IR spectrum of the grafted polystyrene samp...
The physical properties of Methyl Methacrylate grafted Muga silk fiber (9.05 to 25.5% graft) were studied using standard methods. Properties of textile interest such as thermal insulating capacity, tensile properties like breaking load, tenacity, tensile strength, youngϵs modulus, and electrical properties such as electrical resistance were found t...
The alterations in the PSII activity of leaves, subsequent to a mild or severe heat stress were characterized by monitoring the Chl a fluorescence and thermoluminescence emission from intact leaves. The Chl a fluorescence measurements were carried out in leaves adapted to either ‘state I’ or ‘state II’ since under these two conditions the photosynt...
Synechococcus PCC 6301 cells grown in the presence of low sublethal levels of (about 2 μ
m) mercury induced alterations in chlorophyll (Chl) a absorption without significant alterations in phycocyanin. Chl a fluorescence emission in Hg2+ -raised cells showed a large (about 18 nm) blue shift in the peak emission. No major spectral changes in phycobi...
The adaptive ability of thylakoid membranes in response to a stress given in the form of an in situ prolonged partial inhibition of PSII electron transport activity was analyzed. The membranes showed alterations in the structure-function relationship, the most prominent being, an increase in the antenna size of PSII. Analysis of chlorophyll fluores...
Addition of different concentrations of heavy metal ions (Hg2+, Cu2+, Ni2+ and Pb2+) inhibited the photosystem 2 catalyzed electron transport activity (H2O→p-benzo-quinone) of the cyanobacteriumSpirulina platensis. Hg2+ caused the inhibition in electron transport activity in very low concentrations compared to the other metal ions. Hg2+ at this low...
Changes in the excitation energy distrbution between the photosystems have been investigated in response to long-term partial inhibition of Photosystem II (PS II) activity by growing the cells of cyanobacterium Synechococcus PCC 7942 in presence of a PS II inhibitor, SANDOZ 9785 (a pyridazinone derivative, also known as BASF 13.338). Transfer of ex...
The action of SAN 9785 on photosynthetic apparatus was critically examined using Chlorophyll a fluorescence and thermoluminescence measurements. The results show inhibition of photosystem II by SAN 9785 at the acceptor side. The mode of action of SAN 9785 was found to be analogous to that of diuron (DCMU) which inhibits electron transport at the ac...
A heat stable, 12kDa protein was purified to homogeneity from buffalo heart mitochondria. It suppressed hydrolytic activity of membrane bound mitochondrial ATPase and its functional activity was Mg++ and ATP dependent. Maximal inhibition was achieved at slightly acidic pH. Its ability to inhibit ATP hydrolysis was significantly diminished at alkali...
Inhibition of electron transport activities in the spheroplasts ofSynechococcus 6301 by HgCl2 is dependent on the concentration of mercury ions. The inhibition of whole chain electron transport activity occurs at low
concentration of Hg2+ (6 ΜM@#@). This inhibition occurs mostly due to interaction of Hg2+ on plastocyanin. At an elevated concentrati...
A 12kDa, heat stable protein (IF1) inhibiting hydrolytic activity of submitochondrial particles was purified to electrophoretic homogeneity from buffalo heart mitochondria. Specific activity of the purified fraction was > 5000 units/mg. Maximal inhibition was observed at pH 6.0 and was Mg++ and ATP dependent. Circular dichroism studies showed that...
Effect of preheating of beet spinach leaves on chlorophyll a fluorescence yield was analyzed with the help of additional high intensity illumination pulses using a pulse modulated fluorometer. Preheating at mildly elevated temperature (35–45°C) causes a shift in the redox state of secondary donor of photosystem II, possibly due to uncoupling of pho...
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 mol photons m-2 s-1) the thylakoids from NaCl seedlings produced n...
We have shown that mercury affects energy transfer in Spirulina platensis. It inhibits energy transfer from phycocyanin to chlorophyll a by specifically bleaching the -84 chromophore of the chromo protein, phycocyanin (PC), in the cyanobacterium. This effect is observed during short-term exposure of cells to Hg2+ ions. Upon long-term (12 h) exposur...
Synechocystis sp. PCC 6803 when grown in the presence of sublethal (μM) levels of cobalt chloride shows an enhancement of Photosystem II (PS II) catalyzed Hill reaction. This stimulation seems to be induced by cobalt ions as other metal ions inhibit para-benzoquinone catalyzed Hill reaction. At saturating white light intensity, this enhancement is...
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 p...
The presence of low concentrations of cobalt ions (200 μMCoCl2) retarded the growth of the cyanobacterium Spirulina platensis. However, cells grown in the presence of CoCl2 exhibited an enhancement in the levels of phycocyanin and carotenoids, while showed a decrease in the content of chlorophyll a, when compared to the untreated control cells. Thy...
Electron transport activity of beet spinach thylakoids was enhanced in the presence of aliphatic amine, DABCO (1,4-diazobicyclo (2,2,2) octane), a hydrophilic proton trapping agent. The extent of stimulation was pH-dependent and similar to the effect of the uncoupler ammonium chloride on electron transport. The stimulation of whole-chain (H2O-->MV)...
The dark-relaxation kinetics of variable fluorescence, Fv, in intact green leaves of Pisum stativum L. and Dolichos lablab L. were analyzed using modulated fluorometers. Fast (t1/2 = 1 s) and slow (t1/2 = 7-8 s) phases in fv dark-decay kinetics were observed; the rate and the relative contribution of each phase in total relaxation depended upon the...
The effect of varying concentrations of sodium chloride (NaCl) (0, 100, 150 and 200 mM) on seedling growth, pigment composition and the primary photochemical activities in cotyledonary leaves of Brassica juncea cv. DIRA 367 was investigated. NaCl-stress resulted in a considerable decrease in growth of the seedlings without causing any significant c...
Heat-stress-induced photosynthetic electron transport and emission properties were studied in the cyanobacterium Spirulina platensis. Heat treatment of intact cells up to 50 °C did not cause major changes in the absorption and emission properties of both chlorophyll a and phycocyanin. However, above 50 °C, there was a specific bleaching of phycobil...
The presence of L-proline in the reaction mixture enhances the photosystem II (H2O----DCPIP) and whole chain (H2O----MV) catalysed electron transport activities of thylakoids isolated from the cotyledonary leaves of Brassica juncea seedlings raised in the absence and the presence of NaCl. The extent of stimulation in activities was higher in the th...
Diethylhydroxylamine, when added to beet spinach thylakoid membranes in the reaction mixture enhanced both photosystem II mediated dichlorophenolindophenol photoreduction and whole chain electron transport supported by methyl viologen. Diethylhydroxylamine supports dichlorophenolindophenol photoreduction when oxygen evolving complex is inactivated...
Fluorescence emission spectra of cells and membranes of the cyanobacterium Spirulina platensis cooled in the dark to 77 K exhibit an intense Photosystem (PS) I band at 756–759 nm (F758). The presence of a 735 nm band in the excitation spectrum with the same half-band-width (32 nm) as F758 indicates that F758 originates from chlorophyll (Ch1) a abso...
The effect of treatment of wheat plants with Cd2+ ions on the photochemical activity of the primary leaves was examined. Three day-old etiolated seedlings were treated with Cd2+ ions for 24 h in dark, and after this treatment the plants were grown in the light until the primary leaves were fully developed. Cd2+ ions (30–120 μM) induced a significan...
Mercury, at a low concentration (3 μM) caused an enhancement in the intensity of room temperature fluorescence emitted by phycocyanin and induced a blue shift in the emission peak of Spirulina cells indicating the alterations in the energy transfer within the phycobilisomes. In vitro the isolated intact Spirulina phycobilisomes from control cells e...
Changes in the fluorescence yield of chlorophyll were monitored to investigate the effect of HgCl2 on the cyanobacteria Spirulina platensis and Anacystis nidulans; weak modulated light, high intensity actinic light and additional strong sources of illumination were used. Depending on the concentration of HgCl2, three distinct types of change in the...
After preheating of Amaranthus chloroplasts at elevated temperatures (up to 45C), the chlorophyll a fluorescence level under low excitation light rises as compared to control (unheated) as observed earlier in other chloroplasts (Schreiber U and Armond PA (1978) Biochim Biophys Acta 502: 138–151). This elevation of heat induced fluorescence yield is...
Addition of low concentrations of mercury chloride (HgCl 2 to intact cells of the cyanobacterium, Spirulina platensis caused an enhancement in the intensity of fluorescence emitted from phycocyanin at room temperature and induced blue shifts in the emission peak suggestive of changes in energy transfer within the phycobilisomes. HgCl 2 also suppres...
The effect of reduction in leaf water content on the complete chlorophyll α fluorescence transient of Dolichos leaf was monitored using a kinetic fluorescence monitor. Specific and sequential alterations in the profile of the fluorescence transient was observed as leaf water content was progressively decreased. Of all the characteristic, the PS 1 M...
Aging in vivo of primary wheat leaves not only induces loss in chloroplast O2 evolution capacity but also alters the accessibility of the electron transport chain for exogenous electron acceptors and donors. The pH profile of ferricyanide Hill reaction in the presence of uncoupler methylamine shifts to the acidic side, upon leaf aging, close to the...
Exposure of isolated Amaranthus chloroplasts to elevated temperatures (>25 °C for 5 min) induced a stimulation of photosystem I catalyzed electron transport rates only with reduced-dichlorophenolindophenol but not with -tetramethylparaphenylenediamine or -diaminodurene as electron donors. Uncoupler mediated stimulation in dichlorophenolindophenol s...
Aging induced selective changes were monitored both in intact and in detached primary leaves of wheat. We have shown that loss in senescence associated chlorophyll content in the case of wheat leaves, is linked to uniform loss in pigment in chloroplasts and not due to loss in chloroplast number. Analyses of loss of chloroplast absorption spectra bo...
Etiolated wheat seedlings grown at 25 °C were subjected to 35 °C for 48 h. During subsequent greening at 25 °C the pigment accumulation and the appearance of photochemical activities were monitored. The 35 °C-pretreatment retarded pigment accumulation and delayed the appearance of photochemical activities. The 35 °C-pretreatment-induced loss in tot...
Chloroplasts isolated from the primary leaves of wheat seedlings grown under different light in the laboratory as well as
from the leaves of field grown seedlings exhibited distinct rhythmic oscillations in photosynthetic electron transport activities.
Chlorophyll content in the primary leaves of continuous light grown wheat seedlings did not oscil...
Chloroplasts isolated at defined times from the primary leaves of wheat seedlings grown under continuous light as well as 12 h light-dark cycles exhibited endogenous oscillations in photosystem II activity monitored as photoreduction of 2,6-dichlorophenol indophenol with water as electron donor. The 12 h rhythmicity in photoreduction of 2,6-dichlor...
Relation between the chlorophyll loss on unit fresh mass basis and the loss of absorbance maximum at 678 nm of the chloroplast absorption spectrum during senescence was investigated in detached wheat leaves. The measurements of absorption spectrum in all assay intervals were made while maintaining nearly the same number of chloroplasts. We observed...
Citations
... In the lab, Prasanna wanted to examine the effects of crown ether complexes, synthesized at JNU (Sabat et al. 1991a), on spinach PSII membrane fragments and O 2evolving PSII core complexes that we made at NREL. We initially thought that K-crown (18-crown-6 potassium picrate) might bind calcium or affect chloride binding in the PSII membrane, thus interfering with O 2 evolution, but this turned out not to be the case. ...
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... In general, a transient elevation in temperature, usually 10-15°C above ambient, is considered as heat shock or heat stress (Wahid et al., 2007 ) . The severity of heatinduced damage depends not only on the tested systems and the potential for temperature tolerance but also on the temperature gradient and mode of heat application (Bukhov and Mohanty, 1999 ) . Under in vivo conditions, the heat-stress-linked alterations depend on the stage of growth of the photosynthetic tissues. ...
Refere