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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 51 (1912), S. 322-323 
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 1912-05-01
    Print ISSN: 1618-2642
    Electronic ISSN: 1618-2650
    Topics: Chemistry and Pharmacology
    Published by Springer
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of pest science 34 (1961), S. 61-61 
    ISSN: 1612-4766
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Reviews of physiology, biochemistry and pharmacology 1 (1902), S. 32-62 
    ISSN: 1617-5786
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 8 (1972), S. 334-355 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Während der Zeit stärkster Wasseranspannung, am Ende der Trockenzeit, wurde der Einfluß der Klimafaktoren auf Nettophotosynthese, Dunkelatmung und Transpiration von Pflanzen in der Negev-Wüste untersucht. Versuchsobjekte waren Wildpflanzen (Artemisia herba-alba, Hammada scoparia, Noaea mucronata, Reaumuria negevensis, Salsola inermis, Zygophyllum dumosum), Kulturpflanzen der Sturzwasserfarm Avdat (Prunus armeniaca, Vitis vinifera) und künstlich bewässerte Arten (Citrullus colocynthis, Datura metel). 1. Lichtsättigung der Nettophotosynthese findet entsprechend der ungehinderten Enstrahlung am Wüstenstandort zwischen 60 und 90 klx statt. 2. Bei Bezug auf das Trockengewicht der Assimilationsorgane übertreffen die maximalen apparenten Photosyntheseraten der mesomorphen, bewässerten Fflanzen die der Wildpflanzen um das Zehnfache. Im Vergleich zu den übrigen Arten erreichen die Wildpflanzen bei Bezug auf die Oberfläche demgenüber höhere Werte. Bezogen auf den gesamten Chlorophyllgehalt liegen die maximalraten der Nettophotosynthese von Salsola und Noaea in der gleichen Größenordnung wie die von Datura, Citrullus und Wein. Selbst Hammada erreicht höhere Werte als die Aprikose. Daraus wird die hohe Photosynthesefähigkeit der Wildpflanzen am Ende der Trockenzeit deutlich. 3. In Anpassung an die Standortstemperaturen liegt der obere Temperaturkompensationspunkt der Nettophotosynthese bei den Wildpflanzen ungewöhnlich hoch. Mit Werten über 49°C erreicht und überschreitet er die bisher für Blütenpflanzen bekannten Maxima. Hammada weist bei 37°C noch optimale Leistungsfähigkeit auf, und bei einer Temperatur der Assimilationsorgane von 49°C ist die Photosyntheserate erst zu 50% gemindert. 4. Die Blattemperatur beeinflußt den Gaswechsel der Pflanzen auch durch Einwirkung auf den Spaltöffnungszustand. Temperatursenkung führt zu Verminderung, Temperaturerhöhung zu Steigerung des internen Diffusionswiderstandes der Blätter für Wasserdampf. Die Mittagsdepression von Nettophotosynthese und Transpiration der Wüstenpflanzen kann daher auf einer temperaturgesteuerten Spaltöffnungsreaktion beruhen. Es wird diskutiert, inwieweit auch die bei erhöhter Temperatur gleichzeitig vergrößerte Wasserdampfdruckdifferenz zwischen Blattmesophyll und Umgebungsluft auf dem Wege über die peristomatäre Transpiration Spaltöffnungsregelungen bedingen kann. 5. Erhöhung der Temperatur bis in die Nähe der Hitzeresistenzgrenze führt zur Verringerung des Diffusionswiderstandes gegen Wasserdampf, also zu einer Öffnungsreaktion der Stomata. Das verursacht verstärkte Transpirationskühlung. 6. Bei zunehmender Wasseranspannung in den Blättern kann der Diffusions-widerstand für Wasserdampf in Form einer Schwellenreaktion durch Spaltenschluß plötzlich steigen, oder es kommt zur einem kontinuierlichen Anstieg, der mit allmählicher Abnahme von Transpiration und Nettophotosynthese verbunden ist. 7. Bei vielen Pflanzen zeigt sich im Tageslauf eine Zunahme des Diffusions-widerstandes für Wasserdampf, der eine Abnahme der Transpirationsrate, aber keine Depression der Nettophotosynthese entspricht. Der Quotient zwischen CO2-Aufnahme und Wasserabgabe wird im Laufe des Tages also günstiger. Es wird erwogen, ob dieses für Wüstenpflanzen vorteilhafte Reaktionsvermögen auf einer Erhöhung des Mesophyllwiderstandes für den Transpirationsstrom beruhen kann.
    Notes: Summary The influence of climatic factors on net photosynthesis, dark respiration and transpiration was investigated in the Negev Desert at the end of the dry summer period when plant water stress was at a maximum. Species studied included: dominant species of the natural vegetation (Artemisia herba-alba, Hammada scoparia, Noaea mucronata, Reaumuria negevensis, Salsola inermis, Zygophyllum dumosum), cultivated plants receiving rainfall and run-off water during the winter season in the run-off farm Avdat (Prunus armeniaca, Vitis vinifera), and irrigated cultivated plants receiving additional water during the summer season (Citrullus colocynthis, Datura metel). 1. Light saturation of net photosynthesis was reached at 60–90 klx conforming to the high solar radiation intensities of the desert. 2. Maximum rates of CO2 uptake per unit of dry weight for the irrigated mesomorphic plants was ten times that of the wild plants. However, in comparison to the other species, maximal rates of CO2 uptake for wild plants were higher when calculated on a leaf area basis than when represented on a dry weight basis. Maximum rates of net photosynthesis per unit chlorophyll content for some of the wild plants (Salsola and Noaea) were comparable to those of the cultivated Vitis and irrigated Citrullus and Datura, Hammada exhibited even higher rates than Prunus. This demonstrates the great photosynthetic capacity of the wild plants even at the end of the dry season. 3. The upper temperature compensation point for net photosynthesis of the wild plants was unusually high as an adaptation to the temperatures of the habitat. Compensation points higher than 49°C exceed the maxima known so far for other flowering species. Maximum rates of net photosynthesis of Hammada were measured when the temperature of the photosynthetic organs was 37°C; at 49°C photosynthesis was only reduced by 50%. 4. Leaf temperature affects plant gas exchange by influencing stomatal aperture. Diffusion resistance of leaves to water vapour was reduced at low temperatures and increased at high temperatures. Reduction of net photosynthesis and transpiration of desert plants at midday may, therefore, be the result of temperature-induced stomatal closure. The possible influence of peristomatal transpiration on stomatal aperture is also discussed. Peristomatal transpiration is directly related to the vapour pressure gradient between the leaf mesophyll and the ambient air which increases with increasing temperatures. 5. Diffusion resistance to water vapour was reduced at high temperatures approaching the limits of heat resistance, due to increased stomatal aperture. This resulted in greater transpirational cooling. 6. Under conditions of increased leaf water stress, diffusion resistance increased, either by sudden stomatal closure at specific threshold values of water stress or through a continuous increase in resistance. This increased resistance is coupled with decreases in transpiration and photosynthesis. 7. In several plant species increased diffusion resistance during the course of the day caused decreased transpiration without a corresponding decrease in photosynthesis. Under these conditions, the ratio of CO2 uptake to transpiration became more favourable as the day progressed. The possibility that this favourable gas exchange response is the result of an increased mesophyll resistance to water vapour loss is discussed.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 8 (1971), S. 296-309 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Carbon dioxide exchange and transpiration measurements of various wild and cultivated plants were carried out during the dry summer period in 1967 in the Central Negev Desert (Israel). A mobile laboratory used for these investigations is described. Measurements were carried out with conditioned plant chambers which followed either the ambient temperature and humidity or else allowed the experiments to be carried out under constant conditions. The accuracy of the measurements was estimated. The mean error of the determination of the CO2 exchange rate amounts to ±0.07 mg CO2·g-1·h-1. Transpiration rate is measured with an error of ±0.15 g H2O·g-1·h-1. The response time of the instrumentation to reach 90% equilibrium after a change in photosynthesis or transpiration is 7 to 9 minutes. Errors which are caused by changes of quality of incident radiant energy and altered turbulence conditions for the leaves enclosed in the chamber, are discussed.
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  • 7
    ISSN: 1432-1939
    Keywords: δ13C ; δ15N ; Nitrogen assimilation ; Forest decline ; Picea abies ; Stable isotopes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Natural carbon and nitrogen isotope ratios were measured in different compartments (needles and twigs of different ages and crown positions, litter, understorey vegetation, roots and soils of different horizons) on 5 plots of a healthy and on 8 plots of a declining Norway spruce (Picea abies (L.) Karst.) forest in the Fichtelgebirge (NE Bavaria, Germany), which has recently been described in detail (Oren et al. 1988a; Schulze et al. 1989). The δ13C values of needles did not differ between sites or change consistently with needle age, but did decrease from the sun-to the shade-crown. This result confirms earlier conclusions from gas exchange measurements that gaseous air pollutants did no long-lasting damage in an area where such damage was expected. Twigs (δ13C between-25.3 and-27.8‰) were significantly less depleted in 13C than needles (δ13C between-27.3 and-29.1‰), and δ13C in twigs increased consistently with age. The δ15N values of needles ranged between-2.5 and-4.1‰ and varied according to stand and age. In young needles δ15N decreased with needle age, but remained constant or increased in needles that were 2 or 3 years old. Needles from the healthy site were more depleted in 15N than those from the declining site. The difference between sites was greater in old needles than in young ones. This differentiation presumably reflects an earlier onset of nitrogen reallocation in needles of the declining stand. δ15N values in twigs were more negative than in needles (-3.5 to-5.2‰) and showed age- and stand-dependent trends that were similar to the needles. δ15N values of roots and soil samples increased at both stands with soil depth from-3.5 in the organic layer to +4‰ in the mineral soil. The δ15N values of roots from the mineral soil were different from those of twigs and needles. Roots from the shallower organic layer had values similar to twigs and needles. Thus, the bulk of the assimilated nitrogen was presumably taken up by the roots from the organic layer. The problem of separation of ammonium or nitrate use by roots from different soil horizons is discussed.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 82 (1990), S. 427-429 
    ISSN: 1432-1939
    Keywords: Insectivorous plants ; Insect capture ; Leaf growth ; Nitrogen storage ; Drosera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Rates of insect capture increased with leaf area in the insectivorous plant Drosera rotundifolia, and growth of new leaves was related to insect capture. However, increased leaf growth was counterbalanced by leaf abscission which was in turn related to insect capture and leaf growth. Leaf loss equaled leaf growth in plants having natural rate of insect capture. A large proportion of the nitrogen gain from prey was stored in the hypocotyl; it was estimated from feeding experiments that about 24% to 30% of the nitrogen stored in the hypocotyl after winter originated from insect capture in the previous season. The effect of insect capture is discussed in relation to the life cycle of Drosera.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Notes: Abstract The southern Namib desert has a vegetation cover of mainly succulent plants in which species of the Mesembryanthemaceae are predominant. Climatically this area is characterized by hot and dry days, and cool and humid nights with episodic rainfalls only in winter. In this environment a great number of species perform a crassulaceaen acid metabolism (CAM). The responses of these plants to water stress as well as the regulation of CAM in the natural habitat are described and discussed.
    Type of Medium: Electronic Resource
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