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  • 1
    ISSN: 0931-1890
    Keywords: Key words Betula pendula ; Photosynthesis ; Respiration ; Nutrients ; Leaf ontogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  In order to explore ontogenetic variation in leaf-level physiological traits of Betula pendula trees, we measured changes in mass- (A mass) and area-based (A area) net photosynthesis under light-saturated conditions, mass- (RSmass) and area-based (RSarea) leaf respiration, relative growth rate, leaf mass per area (LMA), total nonstructural carbohydrates (TNC), and macro- and micronutrient concentrations. Expanding leaves maintained high rates of A area, but due to high growth respiration rates, net CO2 fixation occurred only at irradiances 〉200 µmol photons m–2 s–1. We found that full structural leaf development is not a necessary prerequisite for maintaining positive CO2 balance in young birch leaves. Maximum rates of A area were realized in late June and early July, whereas the highest values of A mass occurred in May and steadily declined thereafter. The maintenance respiration rate averaged ≈8 nmol CO2 g–1 s–1, whereas growth respiration varied between 0 and 65 nmol CO2 g–1 s–1. After reaching its lowest point in mid-June, leaf respiration increased gradually until the end of the growing season. Mass and area-based dark respiration were significantly positively correlated with LMA at stages of leaf maturity, and senescence. Concentrations of P and K decreased during leaf development and stabilized or increased during maturity, and concentrations of immobile elements such as Ca, Mn and B increased throughout the growing season. Identification of interrelations between leaf development, CO2 exchange, TNC and leaf nutrients allowed us to define factors related to ontogenetic variation in leaf-level physiological traits and can be helpful in establishing periods appropriate for sampling birch leaves for diagnostic purposes such as assessment of plant and site productivity or effects of biotic or abiotic factors.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0931-1890
    Keywords: Key words Scots pine ; Aluminum ; Pollution ; Photosynthesis ; Roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  One-year-old Scots pine (Pinus sylvestris L.) seedlings were grown for 9 weeks in nutrient solutions containing 0, 0.5, 1, 2 and 4 mM aluminum nitrate (Al(NO3)3) at pH 4.2. Nine weeks exposure to Al significantly reduced total plant, shoot and root mass and caused a linear decline in proportional allocation of biomass to roots. Relative growth rate of roots declined to as low as zero. Aluminum treatment decreased calcium and magnesium uptake and increased Al content in roots and needles. After 3 weeks of exposure a 10 – 60% increase in total phenols in roots and a 20 – 40% increase in o-diphenols in roots and needles were noted. Roots affected by Al showed degeneration of meristematic cells, fewer cell divisions, deformation in cell walls and higher lignification and suberization. The majority of root apices were structurally similar to dormant roots, and a premature senescence of the entire root system was observed. Net photosynthetic rate after 6 weeks of treatment was negatively correlated with needle Al content and Al/Ca ratio (r 〈  – 0.9, P 〈 0.1). The results suggest that Scots pine may be more susceptible to Al than was expected based on previous experiments.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 41 (1983), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: During slow-wave sleep, rat brain glycogen increases within a few minutes to about 70% above waking levels. Upon awakening, the increment is lost within 2–5 min. After repeated episodes of sleep, brain glycogen levels are comparable to those observed after only a single episode of sleep. Liver glycogen is unaffected by slow-wave sleep.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Medicine 36 (1985), S. 397-405 
    ISSN: 0066-4219
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 20 (1973), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Labelled inorganic phosphate (32P1) was administered intraventricularly to unrestrained sleeping and waking adult rats. After about 20 min of sleep or a comparable period of wakefulness, as monitored by EEG and EMG, the animals were frozen in liquid nitrogen and the brains were analysed. One group of animals (A) was not previously acclimatized to the apparatus. A second group (B) was acclimatized. The specific radioactivity of a phosphoprotein fraction was elevated during sleep in group A but not in group B. The specific radioactivity of the phosphatides of group B was depressed in sleeping as compared with waking animals. This effect was not observed in group A. No significant difference was detected between the EEG patterns of sleeping animals in groups A and B, as evaluated by standard criteria. These observations suggest that the physiological conditions attributable to environmental, emotional or other determinants can influence shifts in brain metabolism during the sleep-wakefulness cycle.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 19 (1972), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The levels in brain of lactate, pyruvate, creatine phosphate, ATP, ADP and AMP were examined in sleeping and waking adult rats. The animals were monitored electrophysiologically and the biochemical measurements were made after approx. 25 min of sleep or wakefulness. The previous treatment of the animals had a marked effect on the levels of brain metabolites during sleep. In animals not acclimatized to the observation chamber, brain levels of lactate and pyruvate rose during sleep above those in the waking state: creatine phosphate and ATP were depressed somewhat. When the animals were acclimatized by being placed in the observation chamber for at least 2 h on four or more consecutive days prior to the experiment, sleep was accompanied by a depression of brain levels of lactate and pyruvate and slight elevations of brain levels of creatine phosphate and ATP. No significant differences in the EEG recordings were noted between the sleeping rats of the acclimatized and non-acclimatized groups. These observations on the effect of acclimatization on brain metabolism during sleep may have clinical relevance in man.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 13 (1997), S. 0 
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. When Albania emerged from its seclusion in 1991, the scientific community had its first opportunity to interact with its international counterparts. Soil resource assessment was made with systems developed in the early 1950s, laboratory facilities to provide supporting data were poor, and it was recognized that a new assessment was urgently needed.The country faces a major challenge in reforestation and soil conservation against a background of overgrazing by sheep and goats and clearing of trees and scrubs for fuelwood. Even orchard and olive trees were used as fuelwood during the winters of 1990 and 1991. Since then, gully and rill erosion has accelerated on many of the sloping lands. In addition to reforestation and conservation measures to reduce the pressures on the sloping land, it is necessary to enhance productivity on the fertile valley bottom soils where most of the agriculture is confined. In the recent past, grain yields have declined due to reduced fertilizer use (low purchasing capacity), and poor management practices. More recently productivity has slowly improved, but land degradation, particularly erosion, has visibly increased.USDA Natural Resources Conservation Service in collaboration with the Land Resources Institute of Albania, initiated work on a new national soil map through collation of existing information and field studies. The land unit for land use planning, evaluation, and general management decisions, is the Major Land Resource Area (MLRA). Each MLRA encompasses geographically associated soils, the majority of which have broadly similar patterns ofclimate, water resources, and land uses. The MLRAs presented here are based on the soil map of Albania at 1 : 200 000 scale. The MLRA information provides an overview of the landscape and natural resources. It can be used to assess land suitability for various crops, opportunities to achieve self sufficiency in food production, selection of areas for both field crops and highvalue crops for export, and identification of appropriate farming system technologies. Each MLRA will have a set of degradation processes which can be flagged, therefore each of them becomes a unit for decision making with respect to investments in research and mitigating technologies. The task is far from complete. Appropriate databases are needed to support the decisions that are being made at national level. To complement the MLRA and related database, decision support systems are needed for the important task of developing policy options.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 22 (1999), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We tested the hypothesis that acclimation of foliar dark respiration to CO2 concentration and temperature is associated with adjustments in leaf structure and chemistry. Populus tremuloides Michx., Betula papyrifera Marsh., Larix laricina (Du Roi) K. Koch, Pinus banksiana Lamb., and Picea mariana (Mill.) B.S.P. were grown from seed in combined CO2 (370 or 580 μmol mol–1) and temperature treatments (18/12, 24/18, or 30/24 °C). Temperature and CO2 effects were predominately independent. Specific respiration rates partially acclimated to warmer thermal environments through downward adjustment in the intercept, but not Q10 of the temperature–response functions. Temperature acclimation of respiration was larger for conifers than broad-leaved species and was associated with pronounced reductions in leaf nitrogen concentrations in conifers at higher growth temperatures. Short-term increases in CO2 concentration did not inhibit respiration. Growth in the elevated CO2 concentration reduced leaf nitrogen and increased non-structural carbohydrate concentrations. However, for a given nitrogen concentration, respiration was higher in leaves grown in the elevated CO2 concentration, as rates increased with increasing carbohydrates. Across species and treatments, respiration rates were a function of both leaf nitrogen and carbohydrate concentrations (R2 = 0·71, P 〈 0·0001). Long-term acclimation of foliar dark respiration to temperature and CO2 concentration is largely associated with changes in nitrogen and carbohydrate concentrations.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 17 (1994), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We developed a chamberless system to expose branches to elevated concentrations of ozone with little alteration of micro-meteorological conditions. In a 35-year-old stand of sugar maple (Acer saccharum Marsh.), scaffolding and a platform (14 m in height) provided access to 10 branches and ten paired controls within the canopy. Ozone was delivered to the canopy through a manifold and an array of loops (38 cm in diameter) of teflon tubing individually fitted to each branch. Ozone-enriched air was discharged through numerous small holes in each loop positioned beneath the exposed foliage. A sampling system controlled by a microcomputer monitored ozone concentrations for each loop by means of composite air samples from 12 leaves, drawn through small teflon tubes (1.65 mm diameter) attached to the petioles. On average, coefficients of variation for ozone concentrations for the sample points within each branch loop were less than 50%. Between 0900 and 1700 h for 68 d of exposure, the mean hourly ozone concentrations among the branches averaged 95nmol mol−1 (±13SD), about twice the ambient mean. Frequency distributions of mean hourly concentrations during exposure were unimodal and approximately log-normal, comparable to ambient ozone concentrations. The open-air loop system enables exposure of branches to gaseous pollutants under relatively natural conditions.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 18 (1995), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Ozone pollution may reduce net carbon gain in forests, yet data from mature trees are rare and the effects of irradiance on the response of photosynthesis to ozone remain untested. We used an open-air system to expose 10 branches within the upper canopy of an 18-m-tall stand of sugar maple (Acer saccharum Marsh.) to twice-ambient concentrations of ozone (95nmol mol−1, 0900 to 1700, 1 h mean) relative to 10 paired, untreated controls (45nmol mol−1) over 3 months. The branch pairs were selected along a gradient from relatively high irradiance (PPFD 14.5 mol m−2 d−1) to deep shade (0.7mol m−2 d−1). Ozone reduced light-saturated rates of net photosynthesis (Asat) and increased dark respiration by as much as 56 and 40%, respectively. Compared to sun leaves, shade leaves exhibited greater proportional reductions in Asat and had lower chlorophyll concentrations, quantum efficiencies, and leaf absorptances when treated with ozone relative to controls. With increasing ozone dose over time, Asat became uncoupled from stomatal conductance as ratios of internal to external concentrations of carbon dioxide increased, reducing water-use efficiency. Ozone reduced net photosynthesis and impaired stomatal function, with these effects depending on the irradiance environment of the canopy leaves. Increased ozone sensitivity of shade leaves compared to sun leaves has consequences for net carbon gain in canopies.
    Type of Medium: Electronic Resource
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