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  • 1
    Electronic Resource
    Electronic Resource
    Ökophysiologische Untersuchungen an Pflanzen der Namib-Wüste (1980)
    Springer
    Naturwissenschaften 67 (1980), S. 21-28 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00424499
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of nitrogen supply on growth and water-use efficiency of xylem-tapping mistletoes (1984)
    Springer
    Planta 162 (1984), S. 268-275 
    Details
    ISSN: 1432-2048
    Keywords: Host parasite interactions ; Mistletoe ; Nutrient relations (mistletoes) ; Phoradendron ; Water relations (mistletoes)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Xylem-tapping mistletoes are known to have normally a higher rate of transpiration and lower water-use efficiency than their hosts. The relationships between water relations, nutrients and growth were investigated for Phoradendron juniperinum growing on Juniperus osteosperma (a non-nitrogen-fixing tree) and for Phoradendron californicum growing on Acacia greggii (a nitrogen-fixing tree). Xylem sap nitrogen contents were approximately 3.5 times higher in the nitrogen-fixing host than in the non-nitrogen-fixing host. The results of the present study show that mistletoe growth rates were sevenfold greater on a nitrogen-fixing host. At the same time, however, the differences in water-use efficiency between mistletoes and their hosts, which were observed on the non-nitrogen-fixing host did not exist when mistletoes were grown on hosts with higher nitrogen contents in their xylem sap. Growth rates and the accumulation of N, P, K, and Ca as well as values for carbon-isotope ratios of mistletoe tissues support the hypothesis that the higher transpiration rates of mistletoes represent a nitrogen-gathering mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397449
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  • 3
    Electronic Resource
    Electronic Resource
    Rooting depth, water availability, and vegetation cover along an aridity gradient in Patagonia (1996)
    Springer
    Oecologia 108 (1996), S. 503-511 
    Details
    ISSN: 1432-1939
    Keywords: Patagonia-vegetation ; Root distribution ; 13C-, 18O-, D-Isotope composition ; Water ; Plant succession
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Above-and belowground biomass distribution, isotopic composition of soil and xylem water, and carbon isotope ratios were studied along an aridity gradient in Patagonia (44–45°S). Sites, ranging from those with Nothofagus forest with high annual rainfall (770 mm) to Nothofagus scrub (520 mm), Festuca (290 mm) and Stipa (160 mm) grasslands and into desert vegetation (125 mm), were chosen to test whether rooting depth compensates for low rainfall. Along this gradient, both mean above-and belowground biomass and leaf area index decreased, but average carbon isotope ratios of sun leaves remained constant (at-27‰), indicating no major differences in the ratio of assimilation to stomatal conductance at the time of leaf growth. The depth of the soil horizon that contained 90% of the root biomass was similar for forests and grasslands (about 0.80–0.50 m), but was shallower in the desert (0.30 m). In all habitats, roots reached water-saturated soils or ground water at 2–3 m depth. The depth profile of oxygen and hydrogen isotope ratios of soil water corresponded inversely to volumetric soil water contents and showed distinct patterns throughout the soil profile due to evaporation, water uptake and rainfall events of the past year. The isotope ratios of soil water indicated that high soil moisture at 2–3 m soil depth had originated from rainy periods earlier in the season or even from past rainy seasons. Hydrogen and oxygen isotope ratios of xylem water revealed that all plants used water from recent rain events in the topsoil and not from water-saturated soils at greater depth. However, this study cannot explain the vegetation zonation along the transect on the basis of water supply to the existing plant cover. Although water was accessible to roots in deeper soil layers in all habitats, as demonstrated by high soil moisture, earlier rain events were not fully utilized by the current plant cover during summer drought. The role of seedling establishment in determining species composition and vegetation type, and the indirect effect of seedling establishment on the use of water by fully developed plant cover, are discussed in relation to climate change and vegetation modelling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00333727
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of day-to-day changes in root temperature on leaf conductance to water vapour and CO2 assimilation rates of Vigna unguiculata L. Walp. (1982)
    Springer
    Oecologia 52 (1982), S. 116-120 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Leaf gas exchange of Vigna unguiculata was influenced by short-term (day-to-day) changes in soil temperature and the response depended upon the aerial environment. When aerial conditions were constant at 30° C leaf temperature, high air humidity and moderate quantum flux, CO2 assimilation rate and leaf conductance increased with increases in soil temperature from 20 to 35° C, and this response was reversible. Decreases in CO2 assimilation rate and leaf conductance were observed at root temperatures above 30° C when root temperatures were increased from 20° C to 40° C and when air humidity was decreased in steps during the day. In contrast, varying soil temperatures between 20 to 35° C had no influence on gas exchange when shoots were subjected to a wide range of temperatures during each day. The gain ratio ∂A/τE remained constant at different air humidities when root temperature was less than or equal to 30° C indicating optimal gas exchange regulation, but changed with humidity at higher root temperatures. Leaf conductance responded independently from leaf water potential which remained relatively constant during individual experiments. The results indicate that plant responses to high root temperatures may have relevance to plant performance in semi-arid environments. They also illustrate the importance of controlling soil temperatures when studying the responses of potted plants in controlled aerial environments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349019
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  • 5
    Electronic Resource
    Electronic Resource
    A portable steady-state porometer for measuring the carbon dioxide and water vapour exchanges of leaves under natural conditions (1982)
    Springer
    Oecologia 53 (1982), S. 141-145 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A portable porometer is described for measuring the steady-state CO2 and H2O exchange rates of leaves under natural conditions. The porometer has an open gas exchange system which monitors the differences in concentrations of CO2 and H2O entering and leaving a cuvette which is clamped on or around leaves. The cuvette is designed to maintain ambient air temperature and humidity around the leaf. This instrument may also be used to determine CO2 response curves in the field. Examples of diurnal courses are presented for attached leaves of different species having high and low rates of CO2 exchange.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00545656
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  • 6
    Electronic Resource
    Electronic Resource
    Carbohydrate partitioning in relation to whole plant production and water use of Vigna unguiculata (L.) Walp. (1983)
    Springer
    Oecologia 58 (1983), S. 169-177 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Increases in plant biomass are mainly a balance between growth of new leaves and growth of new roots, the new leaves having positive feedback upon the production process and the new roots having positive feedback upon the plant water status. Control of both opposing processes with respect to biomass production may be considered optimal whenever biomass of the plant reaches a maximum without adversely affecting plant water status. This occurs only if all carbohydrates are partitioned into growth of new leaves, unless water uptake is insufficient to meet the additional evaporative demand created by the newly grown leaf area without decreasing the water status of the plant. It is shown by theoretical considerations based upon optimization theory, especially by application of the Pontryagin Maximum Principle, that in this case carbohydrate partitioning is dependent upon the transpiration rate per leaf weight and upon the efficiency of the root at taking up water. Growth of Vigna unguiculata at two levels of air humidity and two levels of water uptake rate by the root was consistent with such a carbohydrate partitioning pattern. Growth of total biomass and its components (leaves, stems, and roots), whole plant transpiration, and the pattern of carbon partitioning were predicted and explained by applying the foregoing principles of optimization in a heuristic model for vegetative growth of an annual.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00399213
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  • 7
    Electronic Resource
    Electronic Resource
    The effect of different growing conditions on water relations parameters of leaf epidermal cells of Tradescantia virginiana L. (1984)
    Springer
    Oecologia 62 (1984), S. 110-117 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Tradescantia virginiana L. plants were cultivated under contrasting conditions of temperature, humidity, light quality and intensity, and nutrient status in order to investigate the effect of growth conditions on the water relations parameters of the leaf epidermal cells. Turgor pressure (P), volumetric elastic modulus (ɛ), half-time of water potential equilibration (T 1/2), hydraulic conductivity (L p ) were measured with the miniaturized pressure probe in single cells of the upper and lower epidermis of leaves. Turgor differed (range: 0.1 bar to 7.2 bar) between treatments with lowest values under warm and humid conditions and additional supply of fertilizer, and highest values under conditions of low air humidity and low nutrient supply. The volumetric elastic modulus changed by 2 orders of magnitude (range: 3.0 bar to 350 bar, 158 cells), but ɛ was only affected by the treatments, in as much as it was dependent on turgor. The turgor dependence of ɛ, measured on intact leaves of T. virginiana, was similar to that for cells of the isolated (peeled) lower epidermis, where ɛ as a function of turgor was linear over the whole range of turgors. This result has implications for the discussion of pressure/volume curves as measured by the pressure bomb where changes in “bulk leaf ɛ” are frequently discussed as “adaptations” to certain treatments. The measurements of the hydraulic conductivity indicate that this parameter varies between treatments (range of means: 2.4×10-6 cm s-1 bar-1 to 13.4×10-6 cm s-1 bar-1). There was a negative correlation for L p in cells of intact leaves as a function of turgor which was altered by the growing conditions. However, a correlation with turgor could not be found for cells from isolated epidermis or cells from a uniform population of plants. The large variation in L p from cell to cell observed in the present and in previous studies was accounted for in a study of 100 cells from a uniform population of plants by the propagation of measurement errors in calculating L p . The results suggest that in T. virginiana cellular water relations are changed mainly by the turgor dependence of ɛ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377383
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  • 8
    Electronic Resource
    Electronic Resource
    Growth, photosynthesis and storage of carbohydrates and nitrogen in Phaseolus lunatus in relation to resource availability (1995)
    Springer
    Oecologia 104 (1995), S. 17-23 
    Details
    ISSN: 1432-1939
    Keywords: Carbohydrate ; Growth ; Nitrogen ; Phaseolus lunatus ; Storage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Growth, photosynthesis, and storage of nitrogen (N) and total non-structural carbohydrates (TNC) of a perennial wild type and an annual cultivar of lima bean (Phaseolus lunatus) were examined at different light intensities and N supplies. Relative growth rate and photosynthesis increased with light and N availability. N limitation enhanced biomass allocation into root rather than into shoot, while light limitation enhanced growth of leaf area. The TNC concentrations increased with light intensity and thus with photosynthesis, while the concentrations of organic N and nitrate decreased. Increasing N supply had the opposite effect. Therefore, TNC and organic N concentrations were negatively correlated (r=−0.90). Pool size of N or TNC increased with N and light availability when either resource was non-limiting, but increased little or remained constant when either resource was limiting. Storage reached a minimum when both resources were supplied at an equal rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365557
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  • 9
    Electronic Resource
    Electronic Resource
    Maximum rooting depth of vegetation types at the global scale (1996)
    Springer
    Oecologia 108 (1996), S. 583-595 
    Details
    ISSN: 1432-1939
    Keywords: Deep roots function ; Terrestrial vegetation ; Biomes ; Plant forms ; Root depth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The depth at which plants are able to grow roots has important implications for the whole ecosystem hydrological balance, as well as for carbon and nutrient cycling. Here we summarize what we know about the maximum rooting depth of species belonging to the major terrestrial biomes. We found 290 observations of maximum rooting depth in the literature which covered 253 woody and herbaceous species. Maximum rooting depth ranged from 0.3 m for some tundra species to 68 m for Boscia albitrunca in the central Kalahari; 194 species had roots at least 2 m deep, 50 species had roots at a depth of 5 m or more, and 22 species had roots as deep as 10 m or more. The average for the globe was 4.6±0.5 m. Maximum rooting depth by biome was 2.0±0.3 m for boreal forest. 2.1±0.2 m for cropland, 9.5±2.4 m for desert, 5.2±0.8 m for sclerophyllous shrubland and forest, 3.9±0.4 m for temperate coniferous forest, 2.9±0.2 m for temperate deciduous forest, 2.6±0.2 m for temperate grassland, 3.7±0.5 m for tropical deciduous forest, 7.3±2.8 m for tropical evergreen forest, 15.0±5.4 m for tropical grassland/savanna, and 0.5±0.1 m for tundra. Grouping all the species across biomes (except croplands) by three basic functional groups: trees, shrubs, and herbaceous plants, the maximum rooting depth was 7.0±1.2 m for trees, 5.1±0.8 m for shrubs, and 2.6±0.1 m for herbaceous plants. These data show that deep root habits are quite common in woody and herbaceous species across most of the terrestrial biomes, far deeper than the traditional view has held up to now. This finding has important implications for a better understanding of ecosystem function and its application in developing ecosystem models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00329030
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  • 10
    Electronic Resource
    Electronic Resource
    15N-ammonium and 15N-nitrate uptake of a 15-year-old Picea abies plantation (1995)
    Springer
    Oecologia 102 (1995), S. 361-370 
    Details
    ISSN: 1432-1939
    Keywords: Picea abies (L.) Karst ; Ammonium ; Nitrate ; 15N ; Tracer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Throughfall nitrogen of a 15-year-old Picea abies (L.) Karst. (Norway spruce) stand in the Fichtelgebirge, Germany, was labeled with either 15N-ammonium or 15N-nitrate and uptake of these two tracers was followed during two successive growing seasons (1991 and 1992). 15N-labeling (62 mg 15N m-2 under conditions of 1.5 g N m-2 atmospheric nitrogen deposition) did not increase N concentrations in plant tissues. The 15N recovery within the entire stand (including soils) was 94%±6% of the applied 15N-ammonium tracer and 100%±6% of the applied 15N-nitrate tracer during the 1st year of investigation. This decreased to 80%±24% and 83%±20%, respectively, during the 2nd year. After 11 days, the 15N tracer was detectable in 1-year-old spruce needles and leaves of understory species. After 1 month, tracer was detectable in needle litter fall. At the end of the first growing season, more than 50% of the 15N taken up by spruce was assimilated in needles, and more than 20% in twigs. The relative distribution of recovered tracer of both 15N-ammonium and 15N-nitrate was similar within the different foliage age classes (recent to 11-year-old) and other compartments of the trees. 15N enrichment generally decreased with increasing tissue age. Roots accounted for up to 20% of the recovered 15N in spruce; no enrichment could be detected in stem wood. Although 15N-ammonium and 15N-nitrate were applied in the same molar quantities (15NH 4 + : 15NO 3 - =1:1), the tracers were diluted differently in the inorganic soil N pools (15NH 4 + /NH 4 + : 15NO 3 - /NO 3 - =1:9). Therefore the measured 15N amounts retained by the vegetation do not represent the actual fluxes of ammonium and nitrate in the soil solution. Use of the molar ammonium-to-nitrate ratio of 9:1 in the soil water extract to estimate 15N uptake from inorganic N pools resulted in a 2–4 times higher ammonium than nitrate uptake by P. abies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00329803
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