The relationship between CO2 assimilation and electron transport in leaves

The inter-relationships between the quantum efficiencies of photosystems I (_I) and II (_II) and the quantum yield of CO₂ fixation % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaciaacaqabeaadaqaaqaaaOqaaiabeA8aMnaaBa% aaleaacaWGdbGaam4tamaaBaaameaacaaIYaaaleqaaaqabaaaaa!3BD3!\[\phi _{CO_2 } \] were investigated in pea (Pisum sativum (L)) leaves with differing rates of photosynthesis using both photorespiratory and non-photorespiratory conditions, and in a leaf of Hedera helix (L) under photorespiratory conditions. The results indicate that under photorespiratory conditions the relationship between % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaciaacaqabeaadaqaaqaaaOqaaiabeA8aMnaaBa% aaleaacaWGdbGaam4tamaaBaaameaacaaIYaaaleqaaaqabaaaaa!3BD3!\[\phi _{CO_2 } \] and both _I and _II is non-linear and variable. The relationship between _I and _II under these circumstances remains predominantly linear. Under non-photorespiratory conditions, leaves with a low rate of photosynthesis due to sink limitation exhibit a non-linear relationship between _I and _II, though the relationship between _I and _II remains linear suggesting a close relationship between linear electron flow and CO₂ fixation. Leaves irradiated at the CO₂ compensation point also exhibit a non-linear relationship between _I and _II. These results suggest that for leaves in air linear electron flow is the predominant source of energy for metabolism. The role of cyclic electron transport is considered when the requirement for the products of linear electron transport is depressed.Abbreviations q_p the coefficient for photochemical quenching of chlorophyll fluorescence - _exe the quantum efficiency of excitation energy capture by open PS II traps - _II the quantum efficiency for electron transport by PS II - _I the quantum efficiency (for electron transport) by PS I - % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaciaacaqabeaadaqaaqaaaOqaaiabeA8aMnaaBa% aaleaacaWGdbGaam4tamaaBaaameaacaaIYaaaleqaaaqabaaaaa!3BD3!\[\phi _{CO_2 } \] the quantum yield for CO₂ fixation (obtained as the gross rate of CO₂ fixation divided by the irradiance) - % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaciaacaqabeaadaqaaqaaaOqaaiabgs5aenaaBa% aaleaacqaH8oqBdaWgaaadbaGaamisamaaCaaabeqaaiabgUcaRaaa% aeqaaaWcbeaaaaa!3CB0!\[\Delta _{\mu _{H^ + } } \] trans-thylakoid proton potential difference - PAQF photosynthetically active quantum flux     

Evaluation of the role of State transitions in determining the efficiency of light utilisation for CO2 assimilation in leaves

Wheat leaves were exposed to light treatments that excite preferentially Photosystem I (PS I) or Photosystem II (PS II) and induce State 1 or State 2, respectively. Simultaneous measurements of CO₂ assimilation, chlorophyll fluorescence and absorbance at 820 nm were used to estimate the quantum efficiencies of CO₂ assimilation and PS II and PS I photochemistry during State transitions. State transitions were found to be associated with changes in the efficiency with which an absorbed photon is transferred to an open PS II reaction centre, but did not correlate with changes in the quantum efficiencies of PS II photochemistry or CO₂ assimilation. Studies of the phosphorylation status of the light harvesting chlorophyll protein complex associated with PS II (LHC II) in wheat leaves and using chlorina mutants of barley which are deficient in this complex demonstrate that the changes in the effective antennae size of Photosystem II occurring during State transitions require LHC II and correlate with the phosphorylation status of LHC II. However, such correlations were not found in maize leaves. It is concluded that State transitions in C₃ leaves are associated with phosphorylation-induced modifications of the PS II antennae, but these changes do not serve to optimise the use of light absorbed by the leaf for CO₂ assimilation.Abbreviations Fm, Fo, Fv maximal, minimal and variable fluorescence yields - Fm, Fv maximal and variable fluorescence yields in a light adapted state - LHC II light harvesting chlorophyll a/b protein complex associated with PS II - q_P photochemical quenching - A₈₂₀ light-induced absorbance change at 820 nm - _{PS I}, _{PS II} relative quantum efficiencies of PS I and PS II photochemistry - _{CO 2} quantum yield of CO₂ assimilation     

The low-light reduction in the quantum yield of photosynthesis: potential errors and biases when calculating the maximum quantum yield

Photosynthesis-irradiance (P-E) curves are widely used to describe photosynthetic efficiency and potential. Contemporary models assume maximal photosynthetic quantum yield () at low irradiances. But P-E observations made with both oxygen evolution and carbon uptake techniques show that this is not always the case. Using new and published data in conjunction with modeling exercises, we demonstrate that regardless of the mechanism there can be reductions in at low irradiances that are not readily observable using conventional P-E analyses. We also show that analytical errors, such as inaccurate estimation of dark oxygen consumption or carbon uptake, can markedly affect the structure of -E curves with negligible effect on P-E curve structure. Whether from respiration `corrections' or other mechanisms, these deviations in at low light levels from the maximum quantum yield of photosynthesis (_max) can lead to significant errors (> 50%) in the estimation of the linear portion of the P-E curve and ultimately _max. Non-linear models of P-E, such as the rectangular hyperbola, quadratic, exponential and hyperbolic tangent that are commonly used to estimate the initial slope () of the P-E curve assume that is maximal at low light levels and therefore can err in the estimation of _max when is reduced at low light levels. Using a diverse data set of 622 P-E curves with a total of 7623 points, we show that although model skills are high (r ² = 0.96 ± 0.05, 0.97 ± 0.04, 0.97 ± 0.04 and 0.97 ± 0.04, respectively), a large fraction of the model-predicted _max differ by greater than 10% from true _max values (91%, 50%, 82% and 46%, respectively). Data from these observations and modeling exercises lead us to suggest that _max be determined by directly estimating the true maximum of a -E curve rather than using the more conventional methodology employing the initial slope of the P-E curve.This revised version was published online in October 2005 with corrections to the Cover Date.     

DNA homology and adsorption specificity of Pseudomonas aeruginosa virulent bacteriophages

Summary The DNA homology and adsorption specificity of newly isolated virulent bacteriophages of P. aeruginosa have been studied. On the basis of this analysis all phages were divided into four groups: k, m, mnP78-like and mnF82-like bacteriophages. DNA's of k as well as m phages were shown to possess different restriction patterns although they have an extensive homology. Unlike other groups, k phages were characterized by the presence of T4 DNA ligase-repaired, single-chain breaks.Abbreviations kbp kilobase pairs - EM electron microscopy     

Activation of peritoneal macrophages in patients with gynecological malignancies by sizofiran and recombinant interferon-γ

We investigated the influence of the combined use of sizofiran, a-1,3-glucan and a recombinant interferon- (rIFN-) upon biological activities of peritoneal macrophages (M). The number of peritoneal M and the production of cytokines (interleukin-1, interferon- and tumor necrosis factor) was increased by the combined treatment. Fully activated peritoneal M based on the increased number of elongated pseudopods were observed by electromicroscope. Sizofiran seems to assure a sufficient supply of M to kill tumor cells in the peritoneal cavity and co-administered rIFN- seems to directly stimulate the accumulated M in addition to its direct cytotoxicity against tumor cells. This combination therapy may be a step to the prevention of the recurrence of gynecological malignancies including ovarian cancer, after a negative second-look laparotomy.Abbreviations rIFN- recombinant interferon- - IL-1 interleukin-1 - TNF tumor necrosis factor - SLL second look laparotomy     

Photon yield of O2 evolution and chlorophyll fluorescence characteristics at 77 K among vascular plants of diverse origins

Photon yields of oxygen evolution at saturating CO₂ were determined for 44 species of vascular plants, representing widely diverse taxa, habitats, life forms and growth conditions. The photonyield values on the basis of absorbed light ( ^a) were remarkably constant among plants possessing the same pathway of photosynthetic CO₂ fixation, provided the plants had not been subjected to environmental stress. The mean ^a value ±SE for 37 C₃ species was 0.106±0.001 O₂·photon^-1. The five C₄ species exhibited lower photon yields and greater variation than the C₃ species ( ^a=0.0692±0.004). The ^a values for the two Crassulaceanacid-metabolism species were similar to those of C₃ species. Leaf chlorophyll content had little influence on ^a over the range found in normal, healthy leaves. Chlorophyll fluorescence characteristics at 77 K were determined for the same leaves as used for the photon-yield measurements. Considerable variation in fluorescence emission both at 692 nm and at 734 nm, was found 1) among the different species; 2) between the upper and lower surfaces of the same leaves; and 3) between sun and shade leaves of the same species. By contrast, the ratio of variable to maximum fluorescence emission at 692 nm (F_v/F_M, 692) remained remarkably constant (The mean value for the C₃ species was 0.832±0.004). High-light treatments of shade leaves resulted in a reduction in both ^a and the F_v/F_M, 692 ratio. The extent of the reductions increased with time of exposure to bright light. A linear relationship was obtained when ^a was plotted against F_v/F_M, 692. The results show that determinations of the photon yield of O₂ evolution and the F_v/F_M, 692 ratio can serve as excellent quantitative measures of photoinhibition of overall photosynthetic energy-conversion system and of photochemistry of photosystem II, respectively. This is especially valuable in field work where it is often impossible to obtain appropriate controls.Abbreviations and symbols CAM Crassulacean acid metabolism - PFD photon flux density (photon fluence rate) - PSI, PSII photosystem I, II - F_o, F_M, F_v instantaneous, maximum, variable fluorescence emission - absorptance - ^a photon yield (absorbed light) - ⁱ photon yield (incident light) C.I.W.-D.P.B. Publication No. 923     

Inhibition of photosynthesis of sunflower leaves by an endogenous solute and interdependence of different photosynthetic reactions

The relationship between components of non-photochemical quenching of chlorophyll fluorescence yield (q_NP) and dissipation of excessive excitation energy was determined in cotton leaves using concurrent measurements of fluorescence and gas-exchange at 2% and 20% O₂ under a range of photon flux densities and CO₂ pressures. A nearly stoichiometric relationship was obtained between dissipation of energy not used in photosynthetic CO₂ fixation or photorespiration and q_NP provided that a component, probably associated with state transitions, was not included in q_NP. Although two distinct components of q_NP were resolved on the basis of their relaxation kinetics, both components appear effective in energy dissipation. The photon yield of open photosystem-II reaction centers decreased linearly with increases in q_NP, indicating that much of the energy dissipation occurs in the pigment bed. However, increases in q_NP appear dependent on the redox state of these centers. The results are discussed in relation to current hypotheses of the molecular basis of non-radiative energy dissipation. It is concluded that determinations of q_NP can provide a quantitative measure of the dissipation of excessive excitation energy if precautions are taken to ensure that the maximum fluorescence yield is measured under conditions that provide complete closure of the photosystem-II reaction centers. It is also concluded that such dissipation can prevent photoinhibitory damage in cotton leaves even under extreme conditions where as much as 80% of the excitation energy is excessive.Abbreviations and symbols F _M, F _O, F _V, F _S fluorescence yield when all PSII centers are closed, when all centers are open, F_M-F_O, at steady state in the light - PFD photon flux density (photon fluence rate) - P(CO₂) sum of rates of CO₂ uptake and dark respiration - P(ET) sum of P(CO₂) and rate of oxygenation - PSI, PSII photosystem I, II - q_NP, q_P non-photochemical, photochemical fluorescence quenching - Q the acceptor for PSII - Q _r/Q _t the fraction of reduced Q or closed PSII centers - _r/ _t intrinsic photon yield of CO₂ fixation in the absence of photorespiration of O₂ evolution - _a P(ET)/PFD (absorbed light) C.I.W. Publication No. 1016     

Effect of<Emphasis Type="Italic"> p</Emphasis>CO<Subscript>2</Subscript> and temperature on the boron isotopic composition of the zooxanthellate coral<Emphasis Type="Italic"> Acropora</Emphasis> sp.

Culture experiments were carried out with Acropora sp. (a branching scleractinian coral) in seawater at two pCO₂ conditions (438 and 725 µatm) and two temperatures (25 and 28 °C) in order to establish the pH and temperature dependence of the boron isotopic composition of the skeleton. A clear pCO₂ effect, but no temperature effect, on the coral boron isotope composition is seen. For corals cultured at normal pCO₂ (438 µatm), the ¹¹B of the skeleton was 24.0±0.2 at 25 °C, and 23.9±0.3 at 28 °C. The values of ¹¹B measured for corals cultured at higher pCO₂ (725 µatm) were lower: 22.5±0.1, and 22.8±0.1 at 25 and 28 °C, respectively. The ¹¹B of corals cultivated at both high and normal pCO₂ conditions are consistent with a dominant pH control, and are very close to that calculated from theoretical considerations. Thus, the corals do not seem to significantly alter ambient seawater for calcification with respect to pH. Co-variation between boron and carbon isotope values is explored.Communicated by: Guest Editor A. Grottoli     

Holling's “hungry mantid” model for the invertebrate functional response considered as a Markov process. Part II: Negligible handling time

In this paper we analyse a stochastic model for invertebrate predation taking account of the predator's satiation. This model approximates Holling's hungry mantid model when handling time is negligible (see Part I). For this model we derive equations from which we can calculate the functional response and the variance of the total catch. Moreover we study a number of approximations which can be used to calculate these quantities in practical cases in a relatively simple manner.List of Notation a rate constant of digestion - b maximum of rate constant of prey encounter in the mantid - c satiation threshold for search - c satiation threshold for pursuit in the mantid - c _i (w^1/2(N- N)ⁱ) - expectation operator - f rate of change of satiation during search - F functional response: mean number of prey eaten per unit of time - g rate constant of prey capture - h probability generating function of N conditional on S = s times p - H probability generating function of N - m_i ¹ - n, N number of prey caught - p probability density of S - p_n simultaneous probability (density) of N and S - q probability of strike success - r dummy variable in generating function - s, S satiation - T _s search time - T _d digestion time - v asymptotic rate of increase of var v - V asymptotic rate of increase of var N - w weight of edible part of prey - W standard Wiener process - x prey density - z (N{S = s}-N)p - rate constant of prey escape time maximum pursuit time - (v{S = + w ^1/2}-v) - present time as a fraction of the time from the start to the end of the experiment - hazard rate of T _s - mean time between (downward) passages of S through c - v w_–1/2(N-) - edible prey biomass density - probability density of , number pi - parameter of Weibull distribution of T _s = (1/2acx(-g(c)))_1/2 - w_–1/2(S -) - satiation in the guzzler approximation: solution to d/dt = f() + g(), (0)=S(0). - biomass functional response: wF - total biomass catch in the guzzler approximation: solution to d/dt = g(), (0) = 0     

Analysing the responses of photosynthetic CO2 assimilation to long-term elevation of atmospheric CO2 concentration

Understanding how photosynthetic capacity acclimatises when plants are grown in an atmosphere of rising CO₂ concentrations will be vital to the development of mechanistic models of the response of plant productivity to global environmental change. A limitation to the study of acclimatisation is the small amount of material that may be destructively harvested from long-term studies of the effects of elevation of CO₂ concentration. Technological developments in the measurement of gas exchange, fluorescence and absorption spectroscopy, coupled with theoretical developments in the interpretation of measured values now allow detailed analyses of limitations to photosynthesisin vivo. The use of leaf chambers with Ulbricht integrating spheres allows separation of change in the maximum efficiency of energy transduction in the assimilation of CO₂ from changes in tissue absorptance. Analysis of the response of CO₂ assimilation to intercellular CO₂ concentration allows quantitative determination of the limitation imposed by stomata, carboxylation efficiency, and the rate of regeneration of ribulose 1:5 bisphosphate. Chlorophyll fluorescence provides a rapid method for detecting photoinhibition in heterogeneously illuminated leaves within canopies in the field. Modulated fluorescence and absorption spectroscopy allow parallel measurements of the efficiency of light utilisation in electron transport through photosystems I and IIin situ.Abbreviations A net rate of CO₂ uptke per unit leaf area (µmol m^–2 s^–1) - A_sat light-saturated A - A₈₂₀ change in absorptance of PSI on removal of illumination (OD) - c CO₂ concentration in air (µmol mol^–1) - c_a c in the bulk air; c_i, c in the intercellular spaces - ce carboxylation efficiency (mol m^–2 s^–1) - E transpiration per unit leaf area (mol m^–2 s^–1) - F fluorescence emission of PSII (relative units) - F_m maximal level of F - F_o minimal level of F upon illumination when PSII is maximally oxidised - F_s the steady-state F following the m peak - F_v the difference between F_m and F_o - F'_m maximal F' generated after the m peak by addition of a saturating light pulse - F'_o the minimal level of F' after the m peak determined by re-oxidising PSII by far-red light - g₁ leaf conductance to CO₂ diffusion in the gas phase (mol m^–2 s^–1) - g'₁ leaf conductance to water vapour diffusion in the gas phase (mol m^–2 s^–1) - k_c and k_o the Michaelis constants for CO₂ and O₂, respectively, (µmol mol^–1); - J_max the maximum rate of regeneration of rubP (µmol m^–2 s^–1) - l stomatal limitation to CO₂ uptake (dimensionless, 0–1) - LCP light compensation point of photosynthesis (µmol m^–2 s^–1) - o_i the intercellular O₂ concentration (mmol mol^–1) - Pi cytosol inorganic phosphate concentration - PSI photosystem I - PSII photosystem II - Q photon flux (µmol m^–2 s^–1) - Q_abs Q absorbed by the leaf - rubisCO ribulose 1:5 bisphosphate carboxylase/oxygenase; rubP, ribulose 1:5 bisphosphate; s, projected surface area of a leaf (m²) - V_c,max is the maximum rate of carboxylation (µmol m^–2 s^–1) - W_c the rubisCO limited rate of carboxylation (µmol m^–2 s¹) - W_j the electron transport limited rate of regeneration of rubP (µmol m^–2 s^–1) - W_p the inorganic phosphate limited rate of regeneration of rubP (µmol m^–2 s^–1) - absorptance of light (dimensionless, 0–1) - _a of standard black absorber ₁, of leaf - _s of integrating sphere walls - , CO₂ compensation point of photosynthesis (µmol mol^–1) - the specificity factor for rubisCO carboxylation (dimensionless) - , convexity of the response of A to Q (dimensionless 0–1) - the quantum yield of photosynthesis on an absorbed light basis (A/Q_abs; dimensionless) - the quantum yield of photosynthesis on an incident light basis (A/Q; dimensionless) - _app the maximum - _m the maximum - _m,app the photochemical efficiency of PSII (dimensionless, 0–1) - _PSII,m the maximum      

The growth of Saccharomyces cerevisiae CBS 426 on mixtures of glucose and ethanol: a model

Saccharomyces cerevisiae CBS 426 was grown in continuous culture in a defined medium with a mixture of glucose and ethanol as carbon source. Growth on ethanol as the sole carbon source was only possible after the addition of a small amount of glutamic acid. The flows of glucose, ethanol, oxygen, carbon dioxide and biomass to and from the system were measured and a model for the growth of the yeast on the carbon sources constructed. The model is shown to allow independent estimation of Y_ATP and P/O. Y_ATP is not independent of the substrate used, but the amount of ATP used in the production of biomass from the monomers is approximately the same for growth on ethanol and on glucose.Nomenclature C chemical state vector - C_i component of the chemical state vector (C-mol) - C_x biomass present in the system (C-mol biomass) - H₂ reduction equivalents (NAD(P)H + H⁺ and FADH₂) - k the amount of ATP required in the production of 1 C-mol of biomass from the monomers (mol ATP/C-mol biomass) - m_ATP maintenance requirement for ATP (mol ATP/C-mol biomass·h) - P/O (=), efficiency of the oxidative phosphorylation (mol ATP/atom O) - r vector of reaction rates - r_i component of the vector of reaction rates (C-mol/h) - r_ATP rate of ATP production (mol ATP/h) - r_x rate of biomass production (C-mol biomass/h) - Y_ATP Y_ATP growth yield on ATP (C-mol biomass/mol ATP) - (Y_ATP)_max maximum growth yield on ATP - stoichiometry matrix - P/O - vector of the flows to the system - _s flow of glucose to the system (C-mol glucose/h) - _o flow of oxygen to the system (mol O₂/h) - _c flow of carbon dioxide to the system (mol CO₂/h) - _x flow of biomass to the system (C-mol biomass/h) - _e flow of ethanol to the system (C-mol ethanol/h) - _w flow of water produced during metabolism (mol H₂O/h)     

Phenogenetic Characterization of a Group of Giant φKZ-like Bacteriophages of Pseudomonas aeruginosa

A comparative study was made of a group ofPseudomonas aeruginosa virulent giant DNA bacteriophages similar to phage KZ in several genetic and phenotypic properties (particle size, particle morphology, genome size, appearance of negative colonies, high productivity, broad spectrum of lytic activity, ability to overcome the suppressing effect of plasmids, absence of several DNA restriction sites, capability of general transduction, pseudolysogeny). We have recently sequenced the phage KZ genome (288 334 bp) [J. Mol. Biol., 2002, vol. 317, pp. 1–19]. By DNA homology, the phages were assigned to three species (represented by phages KZ, Lin68, and EL, respectively) and two new genera (KZ and EL). Restriction enzyme analysis revealed the mosaic genome structure in four phages of the KZ species (KZ, Lin21, NN, and PTB80) and two phages of the EL species (EL and RU). Comparisons with respect to phage particle size, number of structural proteins, and the N-terminal sequences of the major capsid protein confirmed the phylogenetic relatedness of the phages belonging to the KZ genus. The origin and evolution of the KZ-like phages are discussed. Analysis of protein sequences encoded by the phage KZ genome made it possible to assume wide migration of the KZ-like phages (wandering phages) among various prokaryotes and possibly eukaryotes. Since the phage KZ genome codes for potentially toxic proteins, caution must be exercised in the employment of large bacteriophages in phage therapy.     

The skeletal isotopic composition as an indicator of ecological and physiological plasticity in the coral genus<Emphasis Type="Italic"> Madracis</Emphasis>

Three species of the reef coral genus Madracis display skeletal isotopic characteristics that relate to depth, colony topography, and consequently to coral physiology. The joint interpretation of skeletal ¹³C and ¹⁸O provides information on the ecological plasticity and adaptation to depth of a coral species. Isotopic results are most easily understood in terms of kinetic effects, which reduce both ¹⁸O and ¹³C below isotopic equilibrium values, and metabolic effects, which only influence the skeletal ¹³C. Madracis mirabilis is adapted to depths shallower than 20 m, and shows the greatest range in kinetic effects and the strongest metabolic ¹³C enrichments caused by symbiont photosynthesis. Madracis formosa lives deeper than 40 m, and shows a reduced range of kinetic effects and relatively weak metabolic ¹³C enrichments. Madracis pharensis inhabits depths from 5 to >60 m, and does not attain the strength of kinetic effects of either of the other two species, apparently because it is not quite as well adapted to rapid growth at either extreme.     

Effects of CO<Subscript>2</Subscript> concentration on acclimatization and physiological responses of two cultivars of carob tree

This study reports survival and physiological responses of micropropagated Ceratonia siliqua L. cvs. Galhosa and Mulata plants during ex vitro acclimatization under ambient (AC; 330 mol mol^–1) or elevated (EC; 810 mol mol^–1) CO₂ concentration and a photosynthetic photon flux density of 125 mol m^–2 s^–1. CO₂ enrichment during acclimatization did not improve survival rate that was around 80 % for both treatments. Eight weeks after ex vitro transplantation, photosynthetic capacity and apparent quantum yield in acclimatized leaves were higher in comparison with those in in vitro-grown leaves, without any significant difference between CO₂ treatments. Chlorophyll content increased after acclimatization. However, EC led to a decrease in the total amount of chlorophyll in new leaves of both cultivars, compared to those grown at AC. Soluble sugars and starch contents were not markedly affected by growth EC, although starch had significantly increased after transfer to ex vitro conditions. EC induced an increase in the stem elongation and in the effective life of leaves, and a decrease in the number of new leaves.     

The Cause of the Difference in Leaf Net Photosynthetic Rate between Two Soybean Cultivars

To explore the cause of difference in photosynthetic performance between different cultivars of crops, leaf net photosynt rate (P _N) and photosystem 2 (PS2) photochemical efficiency (F_v/F_m), apparent quantum yield of carbon assimilation (_c), electron transport rate, photophosphorylation activity, etc. were measured in two soybean cultivars, Heinong 42 and Heinong 37. At pod setting and filling, significant differences in P _N between them were observed. The former with a higher P _N (from 7 to 38 %) had a significantly higher leaf thickness, leaf dry mass/area (LMA), chlorophyll content, soluble protein content, apparent quantum yield of electron transport through PS2 (_e), carboxylation efficiency (CE), and ribulose-1,5-bisphosphate carboxylase (RuBPC) activity. The significantly higher P _N of Heinong 42 is mainly due to its higher content and activity of RuBPC.     

Isolation of phages infecting<Emphasis Type="Italic"> Actinoplanes</Emphasis> SN223 and characterization of two of these viruses

Phages infecting the industrially important Actinoplanes strain SN223 were isolated from soil samples collected at the shores of inland waters in Germany. The genome sizes range from 53 kb to 58 kb. Preliminary analyses revealed G+C contents comparable with the G/C bias of the host. Electron microscopy of three selected viruses displayed no obvious morphological differences, the phage heads being icosahedral and their tails non-contractible. Two of the phages (Asp2, Asp3.1) characterized in more detail are capable of provoking putative pseudolysogenic growth of the host bacterium. The carrier state for Asp2, in which cells are tightly packed with viruses, was demonstrated by electron microscopy. The latter phage is apparently widely distributed, as it was isolated from regions which are distantly located, i.e. more than 600 km apart from each other.     

Derivation of 13C chemical shift surfaces for the anomeric carbons of oligosaccharides and glycopeptides using ab initio methodology

The dependence between the anomeric carbon chemical shift and the glycosidic bond , dihedral angles in oligosaccharide and glycopeptide model compounds was studied by Gauge-Including Atomic Orbital (GIAO) ab initio calculations. Complete chemical shift surfaces versus and for d-Glcp-d-Glcp disaccharides with (11), (12), (13), and (14) linkages in both - and -configurations were computed using a 3-21G basis set, and scaled to reference results from calculations at the 6-311G^** level of theory. Similar surfaces were obtained for GlcNAcThr and GlcNAcSer model glycopeptides in - and -configurations, using in this case different conformations for the peptide moiety. The results obtained for both families of model compounds are discussed. We also present the determination of empirical formulas of the form ¹³C=f(,) obtained by fitting the raw ab initio data to trigonometric series expansions suitable for use in molecular mechanics and dynamics simulations. Our investigations are consistent with experimental observations and earlier calculations performed on smaller glycosidic bond models, and show the applicability of chemical shift surfaces in the study of the conformational behavior of oligosaccharides and glycopeptides.     

Carbon dioxide and water vapor exchange over a <Emphasis Type="Italic">Miscanthus</Emphasis>-type grassland: Effects of development of the canopy

The eddy correlation technique was employed to measure net ecosystem carbon dioxide (CO₂) (NEE) and water vapor exchange (LE) over a C3/C4 co-occurring wet temperate Miscanthus-type grassland in the Kanto plain of Japan in the 1999 growing season. The maximal mean canopy height and maximal leaf area index were 1.0m and 5.5, respectively. The daily maximal LE was approximately 540Wm^–2. The maximum value of daily accumulative LE was 16.3MJday^–1. Daily variation of the decoupling factor () suggests that in the morning LE decoupled with the atmosphere, and the available energy was the major driving force for LE, whereas in the afternoon LE coupled strongly with the atmosphere, and the atmospheric evaporative demand played a critical role in LE. The decline in (from 0.8 to 0.5) with the growing season demonstrates that LE decoupled from the atmosphere in the later growth season. The peak NEE value was 57.4µmolCO₂m^–2s^–1 (the positive value signifies the canopy carbon gain was from the air). The maximal daily integrated NEE was 1.06molCO₂m^–2day^–1 observed during the peak growth stage. A rectangular hyperbolic model was used to describe the relation between daytime NEE and incident photosynthetic photon flux density (PPFD). The net ecosystem CO₂ was not light-saturated up to a PPFD level of 2000µmol m^–2s^–1. The initial slope estimated with the NEE–PPFD response model was approximately 0.042molCO₂mol^–1photon on average. The canopy light compensation point ranged from 210 to 430µmolm^–2s^–1 with an average of approximately 310µmolm^–2s^–1. Both the initial slope and the canopy light compensation point decreased as the canopy senesced. The switch in dominance from C3 to C4 plants played an important role in the canopy fluxes.     

Large scale preparation of PA-oligosaccharides from glycoproteins using an improved extraction method

We have developed a new method for the large scale preparation of pyridylaminated (PA-) oligosaccharides from glycoproteins. Phenol/chloroform extration was adapted for the removal of protein and excess 2-aminopyridine, improving the efficiency of preparation. From a 2.5 g sample of human apo-transferrin, 25–30 mol of agalacto biantennary PA-oligosaccharide could be obtained. By increasing the concentration of PA-oligosaccharide substrate, we were able to detect a very low level ofN-acetylglucosaminlytransferase IV activity in CHO cell extracts.Abbreviations PA 2-aminopyridine - SDS sodium dodecyl sulfate - GlcNAc N-acetylglucosamine - GnT N-acetylglucosaminyltransferase - Gn,Gn-bi-PA GlcNAc1-2Man1-3(GlcNAc1-2Man1-6)Man1-4GlcNAc1-4GlcNAc-2-aminopyridine - Gn,Gn,Gn-tri-PA GlcNAc1-2(GlcNAc1-4)Man1-3(GlcNAc1-2Man1-6)Man1-4GlcNAc1-4GlcNAc-2-aminopyridine - Gn,Gn,Gn-trí-PA GlcNAc1-2Man1-3({GlcNAc1-2(GlcNAc1-6)Man1-6})Man1-4GlcNac1-4GlcNAc-2-aminopyridine - Gn,(Gn),Gn-bi-PA GlcNAc1-2Man1-3(GlcNAc1-4)(GlcNAc1-2Man1-6)Man1-4GlcNAc1-4GlcNAc-2-aminopyridine     

Isolation and characterization of lytic phages fromBacterioides ruminicola ssbrevis

Two bacteriophages (Brb01 and Brb02), lytic toBacteroides ruminicola ssbrevis AR20, were isolated from sewage water. Both phages possessed polyhedral heads and long noncontractile tails, and were classified as Siphoviridae of morphotype B1. Bacteria resistant to phages Brb01 and Brb02 arose following lysis of broth cultures. Survivors of Brb01 infection were capsulated but remained susceptible to Brb02 infection. Survivors of Brb02 infection were noncapsulated and were resistant to attack by both Brb01 and Brb02. Neither phage lysogenized the host. Both phages contained double-stranded DNA, and their restriction endonuclease digestion patterns indicated that the phage genomes were circularly permuted and terminally redundant. Phage Brb01 genome was examined in greater detail and confirmed to be circularly permuted, of size 33 kb, with a terminal redundancy of 2 kb, or 6% of the length of the genome. Circularly permuted genomes in phages of rumen bacteria do not appear to have been reported previously.At present, there is considerable interest in the genetic manipulation of rumen bacteria. The characterization of the phages described herein provides the basic information required for their use in the construction of vectors for the transfer of genetic material.