Deposition of Erysiphe graminis Conidia on a Barley Crop II. Consequences for Spore Dispersal

Measured deposition rates of Erysiphe graminis conidia are often greater than those calculated from spore fall speed, v^s, and mean wind speed. The predictions of two gradient transfer models of spore dispersal in crops, in which sedimentation and inertial impaction were calculated from v^s and local wind speed or estimated from measured values (Mc Cartney and Bainbridge 1987), were compared. Comparisons of the models suggest that deposition rates close to the source may be underestimated by a factor of two and deposition half distances may be doubled when deposition is calculated conventionally. The results illustrate the importance of accurately describing deposition processes when constructing spore dispersal models.     

Sedimentation velocity of myxomycete spores

Sedimentation velocities were measured for seven myxomycete species and one fungus. Values for these first measurements for Myxomycetes were fitted with the formula of Stoke’s law for the terminal velocity of small spherical bodies in air. The obtained correlation coefficient of R=0.939 indicates that sedimentation velocities of myxomycete spores follow Stoke’s law well. With spore density as a parameter, the fit estimated a mean density of 0.74 g/cm³ for air-dried spores. The importance of the stalked spore case as well as the spore diameter for dispersal abilities of Myxomycetes is discussed.     

The effects of SO2 and O3 fumigation on acid deposition and foliar leaching in the Liphook forest fumigation experiment

The ambient pollution climate at the Liphook forest fumigation site, where coniferous trees were fumigated with SO₂ and O₃, for 4 years under field conditions, was characteristic of the fringes of the areas where pollutant effects are a problem. Experimental treatments increased SO₂ concentrations to levels more characteristic of Eastern Europe, and summer O₃ concentrations by 30%. Deposition of SO₂ to the soil between the trees (inferred from shallow lysimeters) was significant, the deposition velocity being 2–1 mms^?1. Deposition to Scots pine and Sitka spruce canopies was greater, deposition velocities being 8.5 and 9.4 mm s^?1, respectively. These high values may perhaps be explained by co-deposition with NH₃. Calculations assume that dry deposition was the sole source of SO₄^2? gain in throughfall, and that there was no significant retention by the trees. There was a trend for O₃ to enhance SO₂ deposition to both soil and trees. Fumigation with SO₂ led to a significant increase in leaching of cations from foliage. Each species neutralized about 63% of the dry-deposited SO₂, predominantly by ion exchange for Ca and K. Equations are provided which allow calculation of foliar leaching given SO₂ concentrations or SO₄^2? deposition. Fumigation increased the rate of nutrient cycling considerably, without affecting foliar concentrations or damaging the trees. Ozone treatments did not enhance foliar leaching, calling into question some suggested mechanisms for the causes of forest decline.     

Variation in the Settling Velocity of Suspended Particulate Matter in Shallow Lakes,with Special Implications for Mass Balance Modelling

Measurements of sedimentation were combined with water samples to calculate settling velocity of suspended particulate matter (SPM) in lakes. The study sites were open water stations and enclosures in Lake Erken (Sweden) and Lake Balaton (Hungary). Settling velocities were found to vary considerably both inside and outside the enclosures. Within sites, the differences between 25th and 75th percentiles of measured settling velocities of SPM were two‐ or three‐fold. Median settling velocities of SPM ranged from around 0.5 m/d in the enclosures of Lake Erken to more than 8 m/d in the open water of Lake Balaton. Special relevance was attributed to flocculation, which is known to be affected by, e.g., SPM concentration and turbulence. Even though not directly measured, the less turbulent environment inside the enclosures was suggested to explain the low settling velocity compared to the open water environment. Settling velocity apparently correlated with water current speed (r² = 0.66; n = 12). Stepwise multiple linear regressions were used to relate the variability in settling velocity of SPM to the variability of possible controlling factors in a number of data subsets. In most cases, one variable describing the total amount of settling material (e.g., SPM) and one variable reflecting the composition of settling material (e.g., total phosphorus) were chosen. The use of suspended solids concentration to predict settling velocity in mass balance models was discussed. It was found that the mean slope between SPM and v_SPM was close to 0.1 (m⁴d^–1 g^–1). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Photophysiological stress in scleractinian corals in response to short-term sedimentation

Effects of short-term sedimentation on common coastal coral species were investigated in laboratory and field experiments on the Great Barrier Reef (GBR) using pulse-amplitude modulated (PAM) chlorophyll fluorometry. In the laboratory, changes in maximal quantum yields of photosystem II (F_v/F_m) in Montipora peltiformis were examined in response to the amount of sedimentation (79-234 mg cm⁻²) and duration of exposure (0-36 h). In control colonies, F_v/F_m ranged from 0.67 to 0.71, and did not show any temporal trend, while maximum yields of sediment-covered fragments declined steadily and reached levels below 0.1 in most colonies after 36 h coverage. Maximal quantum yield in M. peltiformis declined linearly in relation to both the amount of sediment deposited per unit surface area and the duration of exposure. Zooxanthellae densities and chlorophyll concentrations per unit area of sediment-treated corals decreased in the same manner, however, their responses were not quite as strong as the changes in F_v/F_m. Within the ranges measured, sedimentation stress of colonies exposed to large amounts of sediment for short periods of time was similar to that exposed to low amounts of sediments for prolonged periods of time. Colonies were recovered from short-term, or low-level, sedimentation within <36 h, whereas long-term exposure, or high levels of sedimentation, killed exposed colony parts. Field experiments comparing susceptibilities of common coastal coral species towards sedimentation showed significant reductions in effective quantum yields (ΔF/F_m′) in 9 out of 12 common coastal species after 22 h of exposure. Three out of twelve investigated species were not affected by the experimental application of sediments (Galaxea fascicularis, Fungia crassa, and Pectinia lactuca). Our results suggest that anthropogenic sediment deposition can negatively affect the photosynthetic activity of zooxanthellae and thus the viability of corals. However, the results also showed the ability of corals to compartmentalise sedimentation stress, as the photosynthetic activity only from tissues directly underneath the sediment declined, whereas that of adjacent clean tissues did not change measurably.     

Dynamics of biogenic Si in freshwater tidal marshes: Si regeneration and retention in marsh sediments (Scheldt estuary)

The sequestration and recycling of biogenic silica (BSi) in freshwater tidal marshes was modelled through the combination of short-term year round sediment trap data with a long-term sedimentation model, MARSED. The modelling was implemented through the complete evolution from a young rapidly rising marsh to a marsh with an elevation close to mean high water. BSi in imported suspended matter was higher in summer (10.9 mg BSi g⁻¹ sediment) than winter (7.6 mg BSi g⁻¹ sediment). However, the deposition of BSi on the marsh surface was higher in winter compared to summer, due to the higher sedimentation rates. Deposition of BSi was correlated to the suspended matter deposition. In the old marsh, yearly about 40 g BSi m⁻² was deposited, while in the young marsh deposition could rise up to 300 g m⁻². Young marshes retained up to 85% of the imported biogenic silica. Recycling efficiency (60%) increased drastically for older marshes. The study shows that marshes act as important sinks for BSi along estuaries. The recycling of the imported BSi to DSi in summer and spring is most likely an essential factor in the buffering role of tidal marshes for estuarine DSi concentrations.     

Photoinhibitory responses of the epiphytic bromeliad Guzmania monostachia during the dry season in Trinidad maintain photochemical integrity under adverse conditions

The C₃–CAM epiphytic bromeliad Guzmania monostachia var. monostachia may be exposed to high incident photosynthetically active radiation (PAR) during the dry season in Trinidad, and resultant variations in photochemical efficiency have been investigated for ‘exposed’ (receiving ～100% incident PAR), ‘semi-exposed’ (～60% PAR) and shaded populations under natural conditions. The more succulent leaves of the plants growing fully exposed within the canopy had higher overall CAM activity (measured as ΔH⁺, the dawn-dusk titratable acidity), a smaller proportion of chlorenchyma and lower total chlorophyll content. There was a gradation of morphological and physiological characteristics between these and shaded leaves. Diurnal time-courses of photosynthetic light responses (as O₂ evolution) showed marked variations in apparent quantum yield (AQY) and light-saturated rates for both exposed and semi-exposed populations, dependent on incident PAR during the day. Similar measurements of photosystem II fluorescence characteristics showed that F_v/F_m declined from 0·70 to 0·42 at midday for exposed plants (on a day when total incident PAR was 44 mol photon m^?2), indicating non-photochemical quenching (qNP) of photosynthesis. However, in contrast to AQY determinations, F_v/F_m recovered during the afternoon. The decrease in F_v/F_m was reduced from 0·72 to 0·64 under 24 mol photon m^?2 d^?1. The long–term recovery of photo-synthetic efficiency was assessed for exposed plants placed under three shading regimes (60, 30 and 3% of incident PAR) over a 17-d period. During this time, total chlorophyll content increased from 228 to 515 and 585 μg g^?1 fresh weight (for 3 and 30%, respectively) and chlorophyll a:b declined. While AQY recovery was much longer under the lowest PAR (17d), under 30% PAR both AQY and F_v/F_m had recovered after 2d shading. The differences between timing of recovery for F_v/F_m during diurnal time courses and in the long term suggest that, while quenching associated with PSII recovers rapidly, enzyme activation and/or protein synthesis of other photosynthetic components may be limiting under low PAR. However, it is suggested that the occurrence of qNP on a daily basis may preclude long-term photoinhibitory damage under natural conditions during the dry season.     

Deposition of ammonia to the forest floor under spruce and beech at the Höglwald site

Laboratory and field measurements of the flux of ammonia to forest floor canopies of spruce and beech stands at the Höglwald site in southern Bavaria are reported. Measurements were performed with an open chamber method. A linearity between ammonia concentration and ammonia flux from the atmosphere to the ground floor canopy was detected. Deposition of ammonia showed no saturation even at air concentrations up to 50 g NH₃ m^–3 air. Temperature, water content and the moss layer of the ground floor canopy had a minor influence on the deposition velocity in laboratory experiments. Deposition velocity of ammonia was higher to the spruce (1.3 cm s^–1), and limed spruce ground floor canopy (1.17 cm s^–1) compared to the beech stand (0.79 cm s^–1). In field studies, a diurnal course of the deposition velocity was detected with highest velocities in midday and minor during night times, but not in the climatic chamber. The flux of ammonia to the ground floor canopy was estimated of app. 10 kg N ha^–1 yr^–1 for the soil under spruce, 9 kg N ha^–1 yr^–1 for the limed spruce and 6 kg N ha^–1yr^–1 for the soil under beech. The fluxes are interpreted as fluxes from the atmosphere to the ground canopies of the stands.     

Flow characteristics of a pilot-scale airlift fermentor

The effects of aeration on the flow characteristics of water in a glass pilot-scale airlift fermentor have been examined. The 55-L capacity fermentor consisted of a 15.2-cm-i.d. riser column with a 5.1-cm-i.d. downcomer tube. It was found that the average bubble size diminished with increased aeration. Typically, average bubble sizes ranged from 4.32 mm at a superficial gas velocity of 0.64 cm/s to 1.92 mm at 10.3 cm/s. A gas holdup of 0.19 was attained with superficial gas velocities (v_s) on the order of 10 cm/s, indicating the highly gassed nature of the fluid in the riser section of the fermentor. Circulation velocities of markers placed in the fermentor decreased with increasing aeration rates due to increased turbulence and axial liquid back mixing within the riser section. Actual volumetric liquid circulation rates remained relatively constant (0.36–0.49 L/s) for values of (v_s) up to 10 cm/s. Based on theoretical calculations, the ascending velocity of bubbles in a swarm reached 54 cm/s in the range of (v_s) values studied.     

Deposition of moss spores in relation to distance from parent gametophytes

Abstract

Daily counts were made of spores trapped on microscope slides coated with petroleum jelly and placed on the ground at distances up to 200 em from isolated colonies of Atrichum undulatum and Bryum argenteum. The observations continued for 30–34 days during the annual period of spore release in these species. Estimates of the number of spores released by the colonies were obtained as the product of the numbers of capsules and the difference between the mean numbers of spores present in undehisced capsules at the beginning of the experiment and remaining in dehisced capsules at the end.

Spore deposition over the experimental periods showed a steep gradient, deposition per unit area falling from 4740—14, 230 spores cm_?2 in the centre of the colonies to less than 10 spores cm_?2 200 cm from the edge of the colonies. Despite the steep deposition gradients, however, it was estimated that more than 85% of the spores in A. undulatum, and more than 95% of those in B. argenteum, were dispersed to unknown distances beyond the trapping areas.     

Transport efficiency and deposition velocity of fluidized spores in ventilation ducts

Experiments with dry, fluidized spores were conducted in a test apparatus to delineate the extent of spore contamination and deposition behavior under normal airflow conditions within a ventilation system. The surrogate biological warfare agent used in experiments was the spore-forming bacterium Bacillus atrophaeus. Viable-spore-counting methods were used in the study because they provide the most important number for estimating human health effects. Three common ventilation duct materials were evaluated: flexible plastic, galvanized steel, and internally insulated fiberglass. Transport efficiency ranged from 9 to 13% in steel and fiberglass ducts; transport efficiency was far less (0.1–4%) in plastic duct. Results showed that the deposition of surrogate biological warfare agent was significantly different in the three duct materials evaluated. All experimentally determined, dimensionless deposition velocities were in the range of theoretical predictions for dimensionless roughness, k ⁺=10. All were 10–100 times greater than the velocities predicted for ducts with smoother surfaces, k ⁺=0.1. For plastic duct, greater dimensionless deposition velocities were likely the result of charge forces between spores and surface. However, for the steel duct, a relatively large dimensionless deposition velocity was unexpected. These findings imply that building contamination will likely vary, depending on the specific type of duct material used throughout an affected area. Results of this study may aid in refining existing particle-transport models and remediation activities.     

Liquid fermentation to produce biomass of mycoherbicidal strains of Fusarium oxysporum

Conditions for optimizing spore production, especially chlamydospores, by host-specific mycoherbicidal strains of Fusarium oxysporum causing vascular wilts in coca (Erythroxylum coca) and poppy (Papaver somniferum) were studied in 2.5-1 fermentors. The fermentor dissolved oxygen and pH had significant effects on the growth characteristics of F. oxysporum strains. The effect of the fungal strain, however was not significant for most of the variables studied except for chlamydospore formation. After 14 days of fermentation, the spore types produced were microconidia and chlamydospores, with very little production of macroconidia. While the total viable counts were significantly higher under high than under low dissolved O₂, the chlamydospore counts were significantly higher under low than under high dissolved O₂. The percentage of chlamydospores obtained, as a proportion of total viable was significantly higher when the fermentor pH was increased, than when it was not. Scaling-up the liquid fermentation to 20 l, yielded log₁₀ c = 6.8 (where c = chlamydospores ml⁻¹) after 14 days' fermentation, with biomass viable counts of log₁₀ v∼8.0 (where v = viable counts g⁻¹ air-dried biomass). A single-step liquid fermentation reported in this study increased chlamydospore yields and reduced the time required for their production with techniques currently available from 5 weeks to less than 2 weeks. Received: 24 April 1997 / Received revision: 6 August 1997 / Accepted: 29 August 1997     

<Emphasis Type="Italic">Bacillus amyloliquefaciens</Emphasis> Spore Production Under Solid-State Fermentation of Lignocellulosic Residues

This study was conducted to elucidate cultivation conditions determining Bacillus amyloliquefaciens B-1895 growth and enhanced spore formation during the solid-state fermentation (SSF) of agro-industrial lignocellulosic biomasses. Among the tested growth substrates, corncobs provided the highest yield of spores (47?×?10¹⁰ spores g^?1 biomass) while the mushroom spent substrate and sunflower oil mill appeared to be poor growth substrates for spore formation. Maximum spore yield (82?×?10¹⁰ spores g^?1 biomass) was achieved when 15 g corncobs were moistened with 60 ml of the optimized nutrient medium containing 10 g peptone, 2 g KH₂PO₄, 1 g MgSO₄·7H₂O, and 1 g NaCl per 1 l of distilled water. The cheese whey usage for wetting of lignocellulosic substrate instead water promoted spore formation and increased the spore number to 105?×?10¹⁰ spores g^?1. Addition to the cheese whey of optimized medium components favored sporulation process. The feasibility of developed medium and strategy was shown in scaled up SSF of corncobs in polypropylene bags since yield of 10?×?10¹¹ spores per gram of dry biomass was achieved. In the SSF of lignocellulose, B. amyloliquefaciens B-1895 secreted comparatively high cellulase and xylanase activities to ensure good growth of the bacterial culture.     

Susceptibility of green leaves and green flower petals of CAM orchid <Emphasis Type="Italic">Dendrobium</Emphasis> cv. Burana Jade to high irradiance under natural tropical conditions

Photosynthetic rates of green leaves (GL) and green flower petals (GFP) of the CAM plant Dendrobium cv. Burana Jade and their sensitivities to different growth irradiances were studied in shade-grown plants over a period of 4 weeks. Maximal photosynthetic O₂ evolution rates and CAM acidities [dawn/dusk fluctuations in titratable acidity] were higher in leaves exposed to intermediate sunlight [a maximal photosynthetic photon flux density (PPFD) of 500–600 μmol m⁻² s⁻¹] than in leaves grown under full sunlight (a maximal PPFD of 1 000–1 200 μmol m⁻² s⁻¹) and shade (a maximal PPFD of 200–250 μmol m⁻² s⁻¹). However, these two parameters of GFP were highest in plants grown under the shade and lowest in full sun-grown plants. Both GL and GFP of plants exposed to full sunlight had lower predawn F_v/F_m [dark adapted ratio of variable to maximal fluorescence (the maximal photosystem 2 yield without actinic irradiation)] than those of shade-grown plants. When exposed to intermediate sunlight, however, there were no significant changes in predawn F_v/F_m in GL whereas a significant decrease in predawn F_v/F_m was found in GFP of the same plant. GFP exposed to full sunlight exhibited a greater decrease in predawn F_v/F_m compared to those exposed to intermediate sunlight. The patterns of changes in total chlorophyll (Chl) content of GL and GFP were similar to those of F_v/F_m. Although midday F_v/F_m fluctuated with prevailing irradiance, changes of midday F_v/F_m after exposure to different growth irradiances were similar to those of predawn F_v/F_m in both GL and GFP. The decreases in predawn and midday F_v/F_m were much more pronounced in GFP than in GL under full sunlight, indicating greater sensitivity in GFP to high irradiance (HI). In the laboratory, electron transport rate and photochemical and non-photochemical quenching of Chl fluorescence were also determined under different irradiances. All results indicated that GFP are more susceptible to HI than GL. Although the GFP of Dendrobium cv. Burana Jade require a lower amount of radiant energy for photosynthesis and this plant is usually grown in the shade, is not necessarily a shade plant.     

Mercury dynamics in Tivoli South Bay, a freshwater tidal mudflat wetland in the Hudson River

The accumulation of total mercury (Hg_T) andmethylmercury (MeHg) was evaluated in sediments ofTivoli South Bay, a freshwater tidal mudflat wetlandin the Hudson River National Estuarine ResearchReserve system. Hg_T concentrations in sedimentcores were measured to evaluate the spatialvariability of Hg_T deposition, and to establisha chronology of Hg_T accumulation. Cores takenfrom the northern, middle, and southern sections ofthe bay had similar distribution patterns andconcentrations of Hg_T, suggesting a common sourceof Hg_T throughout the bay. Sedimentconcentrations ranged from 190 to 1040 ng Hg g^–1,2 to 10 times greater than concentrations expected insediments from non-anthropogenic sources. Hg_Tdeposition rates were similar in different regions ofthe bay, and increased from 200 ng Hg cm^–2yr^–1in the 1930s to a maximum of 300 ngHg cm^–2 yr^–1 in the 1960s. Deposition rateshave steadily declined since the 1970s and arecurrently at 80 ng Hg cm^–2 yr^–1. Transportof Hg_T by tidal waters from the Hudson River islikely the main source of Hg_T in the bay.Distribution patterns and absolute concentrations ofMeHg in sediment cores were similar throughout thebay, with concentrations ranging from 0.43 to 2.95ng g^–1. Maxima in MeHg concentration profilesoccurred just below the sediment-water interface andat a depth of 30 cm. The maximum at 30 cm wascoincident with maximum Hg_T concentrations. MeHgconcentrations in suspended particulate matter (SPM)from the Hudson River suggest that MeHg in the baycould be derived from riverine SPM rather than formedin situ.     

Specific features of the kinetics of H2-O2-O2(a 1Δ g ) mixtures: I. formation and quenching of electronically and vibrationally excited (A′) molecules in H2-O2-O2(A 1Δ g ) mixtures at a temperature of 300 K

Available data on the kinetic processes in H₂-O₂-O₂(a ¹Δ _g ) mixtures are analyzed theoretically, and the ranges in which the rate constants of these processes can vary are determined. The processes of energy transformation in an O₂(a ¹Δ _g )-H₂-H-HO₂ system in the approximations of the fast and slow (in comparison with the vibrational relaxation time of the HO₂ radical) quenching of the electronically excited state are considered. The experiments on the quenching of singlet delta oxygen (SDO) molecules O₂(a ¹Δ _g ) excited in a microwave discharge at a temperature of 300 K and pressure of 6 Torr in a lean hydrogen-oxygen mixture are simulated (by a lean fuel mixture is meant a mixture in which the ratio of the fuel to the oxidizer mass fraction is less than the stoichiometric ratio, which is 2: 1 for a hydrogen-oxygen mixture). It is shown that, over the experimental observation times, the SDO quenching frequency depends on the concentration of molecular hydrogen, the residual odd oxygen fraction in the gas flow, and the ratio between the rate constants of kinetic processes involving HO₂ and HO₂* radicals. Simulations of the microwave discharge and the transport of excited oxygen along the drift tube make it possible to determine the residual odd oxygen concentration in the gas flow. Recommendations on the choice of the rate constants for the O₂(a ¹Δ _g ) + HO₂)A″, v₃″ = 0) ? O₂ + HO₂*(A′, v₃′ = 1), HO₂*(A′v₃′ ≤ 1) + O₂(a ¹Δ _g ) → HO₂*(A′,v₃′ ≥ 6) + O₂, and HO₂*(A′,v₃′ ≤ 1) + O₂(a ¹Δ _g ) → H + O₂ + O₂ processes are given. It is shown that, in the case of slow quenching in a H₂-O₂-O₂(a ¹Δ _g ) mixture at a low temperature, the intensity of hydrogen oxidation is enhanced due to the reaction + HO₂*(A′,v₃′ ≤ 1) + O₂(¹Δ) → H + O₂ + O₂.     

Dispersal of Erysiphe graminis and Lycopodium clavatum spores near to the source in a barley crop

In experiments to study dispersal of spores in a crop of barley, a 4-m wide strip of the cultivar Zephyr (a mildew-susceptible variety) was a source of mildew (Eyrsiphe graminis) conidia. Small suction traps, previously calibrated in a wind tunnel, were used to measure spore concentration within and above the crop. Large concentrations of conidia were measured in the crop at the downwind edge of the Zephyr strip but these decreased rapidly with distance downwind. At 1 m concentrations were halved and by 4 m they were no greater than the background concentration measured in the crop upwind of the source. Next to the source, concentrations were much greater within than above the crop and net spore movement (flux) was upwards out of the crop; by 4 m downwind concentrations were greater above the crop and spore flux was reversed. Lycopodium clavatum spores were released in the same crop from a line of point sources. Concentrations also decreased rapidly downwind but, with no background of spores, numbers remained greater within than above the crop further from the source than for E. graminis. Even so by 7 m downwind concentrations in the crop had declined to less than those above. Deposition of L. clavatum spores onto horizontal glass slides in the crop agreed with that expected by settling. However, impaction onto vertical cylinders among plants was much greater than predicted. The reason is not known although turbulent air-flow around plants may, in some way, enhance impaction. Many E. graminis conidia near the source were deposited in clumps. This prevented any accurate prediction of deposition rates as fall speeds of clumps (necessary for prediction) were not known. Not surprisingly, deposition on horizontal slides often exceeded that expected from settling of single spores although it was not always greatest where clumps predominated. The proportion of spores deposited on vertical cylinders and horizontal slides located among plants ranged from 0–02 to 0–27 and from 0–019 to 0–127 of the area dose, respectively. Although these may seem to be small trapping efficiencies, the same deposition rates in a crop with many leaves and stems would rapidly filter most spores from air in the crop and can explain why concentrations were observed to decline so rapidly.     

Measurements of the gas temperature in an oxygen plasma by spectroscopy of the O2( b 1Σ g+ ) → O2( X 3Σ g? ) transition

A method for measuring the gas temperature in an oxygen plasma by spectroscopy of the electronic transition from the O₂(b ¹Σ _g ⁺ , v = 0) metastable state of molecular oxygen into the O₂(X ³Σ _g ⁻ , v = 0) ground state is considered in detail. The method is verified experimentally for the plasma of dc glow discharge in pure oxygen. It is shown that the gas temperature can be determined by analyzing high-resolution spectra of the P branch of this transition, no matter whether its fine structure (^P P and ^P Q branches) is resolved or masked, provided that the rotational structure of the spectrum is resolved. The feasibility of the method proposed in 1999 by P. Maco and P. Veis for determining the gas temperature from the ratio between the intensity maxima of the R and P branches of the O₂(b ¹Σ _g ⁺ , v = 0) → O₂(X ³Σ _g ⁻ , v = 0) transition in a poorly resolved spectrum was studied experimentally. It is shown that, in order to use this method, it is necessary to know the spectrograph instrumental function. The effect of the spatial inhomogeneity of the temperature and concentration of O₂(b ¹Σ _g ⁺ ) molecules on the accuracy of integral (over the plasma volume) measurements of the gas temperature is investigated using spatially resolved spectroscopy of the O₂(b ¹Σ _g ⁺ , v = 0) → O₂(X ³Σ _g ⁻ , v = 0) transition. It is shown that precise measurements of the temperature require that the optical measurement system be thoroughly adjusted in order for the temperature and concentration of the emitting particles to vary insignificantly over the optically selected volume. Original Russian Text ? S.M. Zyryanov, D.V. Lopaev, 2007, published in Fizika Plazmy, 2007, Vol. 33, No. 6, pp. 563–574.     

The Photosynthesis and Chlorophyll a Fluorescence in Seedlings of Kandelia Candel (L.) Druce Grown under Different Nitrogen and NaCl Controls

Kandelia candel (L.) Druce is the dominant mangrove species on the west coast of northern Taiwan. We have measured the net photosynthetic rate (P _N) and chlorophyll (Chl) a fluorescence of seedlings grown at combinations of two nitrogen (0.01 and 0.1 mM) and two NaCl (250 and 430 mM NaCl) controls. With the same nitrogen level, seedlings grown at higher salinity (HS) had a significantly lower P _N and stomatal conductance (g _s) than those at lower salinity (LS). An increase in nitrogen availability significantly elevated P _N and g _s of the LS-grown seedlings. Compared to dark adapted leaves, the maximum quantum yield of photosystem 2 (PS2) (F_v/F_m) of leaves exposed to PFDs of 1200 and 1600 μmol m^-2 s^-1 for 2 h was significantly reduced. The degree of F_v/F_m reduction differed among leaves of the four types of treated plants. Chl fluorescence quenching analysis revealed differences among the examined plants in coefficients of non-photochemical and photochemical quenching. This revised version was published online in June 2006 with corrections to the Cover Date.     

Physiological responses to nitrogen and sulphur addition and raised temperature in <Emphasis Type="Italic">Sphagnum balticum</Emphasis>

Sphagnum, the main genus which forms boreal peat, is strongly affected by N and S deposition and raised temperature, but the physiological mechanisms behind the responses are largely unknown. We measured maximum photosynthetic rate (NP_max), maximum efficiency of photosystem II [variable fluorescence (F _v)/maximum fluorescence yield (F _m)] and concentrations of N, C, chlorophyll and carotenoids as responses to N and S addition and increased temperature in Sphagnum balticum (a widespread species in the northern peatlands) in a 12-year factorial experiment. NP_max did not differ between control (0.2 g N m⁻² year⁻¹) and high N (3.0 g N m⁻² year⁻¹), but was higher in the mid N treatment (1.5 g N m⁻² year⁻¹). N, C, carotenoids and chlorophyll concentration increased in shoot apices after N addition. F _v/F _m did not differ between N treatments. Increased temperature (+3.6°C) had a small negative effect on N concentration, but had no significant effect on NP_max or F _v/F _m. Addition of 2 g S m⁻² year⁻¹ showed a weak negative effect on NP_max and F _v/F _m. Our results suggest a unimodal response of NP_max to N addition and tissue N concentration in S. balticum, with an optimum N concentration for photosynthetic rate of ~13 mg N g⁻¹. In conclusion, high S deposition may reduce photosynthetic capacity in Sphagnum, but the negative effects may be relaxed under high N availability. We suggest that previously reported negative effects on Sphagnum productivity under high N deposition are not related to negative effects on the photosynthetic apparatus, but differences in optimum N concentration among Sphagnum species may affect their competitive ability under different N deposition regimes.