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  • 1
    Electronic Resource
    Electronic Resource
    Isotopic heterogeneity of water in transpiring leaves: identification of the component that controls the δ18O of atmospheric O2 and CO2 (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 17 (1994), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Two direct but independent approaches were developed to identify the average δ18O value of the water fraction in the chloroplasts of transpiring leaves. In the first approach, we used the δ18O value of CO2 in isotopic equilibrium with leaf water to reconstruct the δ18O value of water in the chloroplasts. This method was based on the idea that the enzyme carbonic anhydrase facilitates isotopic equilibrium between CO2 and H2O predominantly in the chloroplasts, at a rate that is several orders of magnitude faster than the non-catalysed exchange in other leaf water fractions. In the second approach, we measured the δ18O value of O2 from photosynthetic water oxidation in the chloroplasts of intact leaves. Since O2 is produced from chloroplast water irreversibly and without discrimination, the δ18O value of the O2 should be identical to that of chloroplast water. In intact, transpiring leaves of sunflower (Helianthus annuus cv. giant mammoth) under the experimental conditions used, the average δ18O value of chloroplasts water was displaced by 3—10 % (depending on relative humidity and atmospheric composition) below the value predicted by the conventional Craig & Gordon model. Furthermore, this δ18O value was always lower than the δ18O value that was measured for bulk leaf water. Our results have implications for a variety of environmental studies since it is the δ18O value of water in the chloroplasts that is the relevant quantity in considering terrestrial plants influence on the δ18O values of atmospheric CO2 and O2, as well as in influencing the δ18O of plant organic matter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1994.tb00267.x
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  • 2
    Electronic Resource
    Electronic Resource
    Interactions between irradiance, nitrogen nutrition, and water stress in the sun-shade responses of Solanum dulcamara (1983)
    Springer
    Oecologia 57 (1983), S. 316-321 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When grown with adequate water and nitrogen (12 mM NO 3 - ) four clones of Solanum dulcamara from sun or shade habitats in Europe showed similar potential for acclimation of photosynthesis to irradiance level during growth. When grown with limiting nitrogen (0.6 mM NO 3 - ) all clones showed a low potential for acclimation of photosynthesis to irradiance during growth. If limiting nitrogen was accompanied by water stress at high irradiance, the initial slope of the irradiance response curve, and the irradiance saturated rate of photosynthesis were depressed, especially in a clone from a shaded habitat. These interactions are discussed in terms of earlier reports on the sunshade responses and sun-shade ecotypic differentiation in this species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377174
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  • 3
    Electronic Resource
    Electronic Resource
    Stomatal mechanism as the basis of evolution of crassulacean acid metabolism (1985)
    [s.l.] : Nature Publishing Group
    Nature 314 (1985), S. 200-200 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] KEELEY ET AL. REPLY-We agree with Cockburn that, although the presence of CAM in astomatous Stylites does not support his theory on the stomatal origin of CAM, it does not necessarily falsify the theory either. We also agree with Thomas that Stylites most reasonably should be included with ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/314200c0
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  • 4
    Electronic Resource
    Electronic Resource
    Comparisons of δ13C values in leaves of aquatic macrophytes from different habitats in Britain and Finland; some implications for photosynthetic processes in aquatic plants (1981)
    Springer
    Oecologia 50 (1981), S. 117-124 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The δ13C values of submerged aquatic plants from contrasting but relatively defined habitats, and the δ13C values of emergent, floating and submerged leaves of dimorphic aquatic plants, were measured. In many instances the δ13C values of dissolved inorganic carbon in the water were also measured. Plant δ13C values in the vicinity of-40 to-50‰ were found in rapidly flowing spring waters with carbonate δ13C values of-16 to-21‰, consistent with the notion that species such as Fontinalis antipyretica almost exclusively assimilate free CO2 via RuP2 carboxylase. Plant δ13C values in the vicinity of-10 to-15‰ in sluggish water with carbonate δ13C values of about-5‰ were observed, consistent with the notion that boundary layer diffusion and/or HCO3 - uptake may determine the δ13C value of submerged aquatic plants in these circumstances. Comparisons of δ13C values of the same or related species growing in waters of similar carbonate δ13C value but different flow rates confirmed this view; more negative δ13C values were frequently associated with plants in fast moving water. In Britain, but not in Finland, the δ13C values of submerged leaves of dimorphic plants were almost invariably more negative than in aerial leaves. The δ13C value of carbonate from chalk streams and in acid springs indicate substantial inputs of respiratory CO2, as opposed to atmospheric carbon. The contributions of these variations in δ13C of the carbon source, and of isotope fractionation in diffusion, to the δ13C value of submerged parts of dimorphic plants is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00378804
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  • 5
    Electronic Resource
    Electronic Resource
    Nitrogen supply as a factor influencing photoinhibition and photosynthetic acclimation after transfer of shade-grown Solanum dulcamara to bright light (1986)
    Springer
    Planta 168 (1986), S. 563-570 
    Details
    ISSN: 1432-2048
    Keywords: Nitrogen nutrition and photosynthesis ; Photoinhibition of photosynthesis ; Photosynthesis (acclimation) ; Solanum (photosynthetic acclimation)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have compared the ability of shadegrown clones of Solamum dulcamara L. from shade and sun habitats to acclimate to bright light, as a function of nitrogen nutrition before and after transfer to bright light. Leaves of S. dulcamara grown in the shade with 0.6 mM NO 3 - have similar photosynthetic properties as leaves of plants grown with 12.0 mM NO 3 - . When transferred to bright light for 1–2 d the leaves of these plants show substantial photoinhibition which is characterized by about 50% decrease in apparent quantum yield and a reduction in the rate of photosynthesis in air at light saturation. Photoinhibition of leaf photosynthesis is associated with reduction in the variable component of low-temperature fluorescence emission, and with loss of in-vitro electron transport, especially of photosystem II-dependent processes. We find no evidence for ecotypic differentiation in the potential for photosynthetic acclimation among shade and sun clones of S. dulcamara, or of differentiation with respect to nitrogen requirements for acclimation. Recovery from photoinhibition and subsequent acclimation of photosynthesis to bright light only occurs in leaves of plants provided with 12.0 mM NO 3 - . In these, apparent quantum yield is fully restored after 14 d, and photosynthetic acclimation is shown by an increase in light-saturated photosynthesis in air, of light-and CO2-saturated photosynthesis, and of the initial slope of the CO2-response curve. The latter changes are highly correlated with changes in ribulose-bisphosphate-carboxylase activity in vitro. Plants supplied with 0.6 mM NO 3 - show incomplete recovery of apparent quantum yield after 14 d, but CO2-dependent leaf photosynthetic parameters return to control levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392277
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  • 6
    Electronic Resource
    Electronic Resource
    Fluorescence quenching during photosynthesis and photoinhibition of Ulva rotundata blid. (1993)
    Springer
    Planta 190 (1993), S. 97-106 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll fluorescence ; Photoinhibition ; Photoprotection ; Ulva (photosynthesis)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationships between photoinhibition and photoprotection in high and low-light-grown Ulva were examined by a combination of chlorophyll-fluorescence-monitoring techniques. Tissues were exposed to a computer-controlled sequence of 5-min exposures to red light, followed by 5-min darkness, with stepwise increases in photon flux. Coefficients of chlorophyll fluorescence quenching (1−qP and NPQ) were calculated following a saturating pulse of white light near the end of each 5-min light treatment. Dark-adapted chlorophyll fluorescence parameters (F0 and FV/FM) were calculated from a saturating pulse at the end of each 5-min dark period. Low-light-grown Ulva showed consistently higher 1−qP, i.e. higher reduction status of Q (high primary acceptor of photosystem II), and lower capacity for nonphotochemical quenching (NPQ) at saturating light than did high-light-grown plants. Consequently, low-light plants rapidly displayed photoinhibitory damage (increased F0) at light saturation in seawater. Removal of dissolved inorganic carbon from seawater also led to photoinhibitory damage of high-light-grown Ulva at light saturation, and addition of saturating amounts of dissolved inorganic carbon protected low-light-grown plants against photoinhibitory damage. A large part of NPQ was abolished by treatment with 3 mM dithiothreitol and the processes so inhibited were evidently photoprotective, because dithiothreitol treatment accelerated photoinhibitory damage in both low- and high-light-grown Ulva. The extent of photoinhibitory damage in Ulva was exacerbated by treatment with chloramphenicol (1 mM) without much effect on chlorophyll-quenching parameters, evidently because this inhibitor of chloroplast protein synthesis reduced the rate of repair processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195680
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  • 7
    Electronic Resource
    Electronic Resource
    Stem photosynthesis in a desert ephemeral, Eriogonum inflatum (1987)
    Springer
    Oecologia 72 (1987), S. 533-541 
    Details
    ISSN: 1432-1939
    Keywords: δ13C ; Eriogonum inflatum ; Great Basin ; Mojave ; Photosynthetic morphology ; Stem photosynthesis ; Water-use efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Seasonal patterns in plant morphology, phenology, and physiology were monitored in several populations of Eriogonum inflatum, a desert ephemeral which produces a large photosynthetic inflorescence above a basal leaf rosette. Green stems accounted for 66–77% of whole plant photosynthetic surface area when integrated over a developmental cycle, whereas only 40–67% of the yearly transpirational water loss could be attributed to stems. Stems were found to have lower nitrogen and chlorophyll contents than leaves, and lower stomatal conductance under all physiological conditions encountered. However, because stems occur later in the year than leaves, comparison of physiological patterns was complicated by the two structures being exposed to different climatic regimes during their developmental cycles. Stems exhibited higher δ13C values than leaves, indicating that stems operated at higher water-use efficiencies than leaves, at least during periods when both leaves and stems were present. Higher water-use efficiency in stems of E. inflatum is attributed to both more conservative water use patterns and to their vertical orientation, allowing stems to remain photosynthetically active longer into the dry season after senescence of the horizontal leaf rosette.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00378979
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  • 8
    Electronic Resource
    Electronic Resource
    Stem photosynthesis in a desert ephemeral, Eriogonum inflatum (1987)
    Springer
    Oecologia 72 (1987), S. 542-549 
    Details
    ISSN: 1432-1939
    Keywords: Eriogonum inflatum ; Internal CO2 concentration ; Stem photosynthesis ; Water-use efficiency ; Water stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The gas exchange characteristics of photosynthetic tissues of leaves and stems of Eriogonum inflatum are described. Inflated stems were found to contain extraordinarily high internal CO2 concentrations (to 14000 μbar), but fixation of this internal CO2 was 6–10 times slower than fixation of atmospheric CO2 by these stems. Although the pool of CO2 is a trivial source of CO2 for stem photosynthesis, it may result in higher water-use efficiency of stem tissues. Leaf and stem photosynthetic activities were compared by means of CO2 fixation in CO2 response curves, light and temperature response curves in IRGA systems, and by means of O2 exchange at CO2 saturation in a leaf disc O2 electrode system. On an area basis leaves contain about twice the chlorophyll and nitrogen as stems, and are capable of up to 4-times the absolute CO2 and O2 exchange rates. However, the stem shape is such that lighting of the shaded side leads to a substantial increase in overall stem photosynthesis on a projected area basis, to about half the leaf rate in air. Stem conductance is lower than leaf conductance under most conditions and is less sensitive to high temperature or high VPD. Under most conditions, the ratio C i /C a is lower in stems than in leaves and stems show greater water-use efficiency (higher ratio assimilation/transpiration) as a function of VPD. This potential advantage of stem photosynthesis in a water limited environment may be offset by the higher VPD conditions in the hotter, drier part of the year when stems are active after leaves have senesced. Stem and leaf photosynthesis were similarly affected by decreasing plant water potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00378980
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  • 9
    Electronic Resource
    Electronic Resource
    Photoinhibition and recovery in tropical plant species: response to disturbance (1994)
    Springer
    Oecologia 97 (1994), S. 297-307 
    Details
    ISSN: 1432-1939
    Keywords: Photoinhibition ; Rainforest disturbance Photosynthesis ; Leaf turnover
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Disturbance or rainforest is often followed by mass mortality of understorey seedlings. Transitions of shade grown plants to full sunlight can cause reductions in the efficiency with which light is used in photosynthesis, called photoinhibition. In order to assess the influence of photoinhibition on mortality and growth after rainforest disturbance this study examined photoinhibition in both simulated and real forest disturbances in northern Papua New Guinea. In an experiment simulating rainforest disturbance, exposure of shade-grown plants to full sunlight resulted in abrupt decreases in the chlorophyll fluorescence parameter F v/F m that is characteristic of photoinhibition. However, in the well-watered plants used in these experiments there were no fatalities during 3 weeks after exposure to full sunlight. Thus, it is unlikely that photoinhibition, alone, is responsible for seedling fatalities after rainforest disturbances, but more likely that fatalities are due to photoinhibition in conjunction with other environmental stress. There were differences between the response of species to the simulated disturbance that concurred with their preferred habitats. For example, species form the genus Barringtonia, which is commonly found in shaded understorey environments, underwent greater reductions in F v/F m and were slower to recover than species that usually inhabit high solar radiation environments. The extent of photoinhibition and the rate of recovery appeared to be dependent on avoidance of direct solar radiation by altering leaf angles and on increasing maximum photosynthetic rates. A field survey of photoinhibition in man-made rainforest gaps corroborated the findings of the simulated disturbance experiment showing that plant species commonly found in shaded environments showed a greater degree of photoinhibition in forest gaps at midday than those species which are classified as species that benefit from gaps or specialist gap inhabitors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317318
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  • 10
    Electronic Resource
    Electronic Resource
    Crassulacean acid metabolism in the shade. Studies on an epiphytic fern, Pyrrosia longifolia, and other rainforest species from Australia (1986)
    Springer
    Oecologia 68 (1986), S. 224-230 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Crassulacean acid metabolism (CAM) was studied in a tropical epiphytic fern, Pyrrosia longifolia, from a fully sun-exposed and from a very shaded site in Northern Queensland, Australia. Measurements of instantaneous net CO2 exchange showed carbon gain via CO2 dark fixation with some net CO2 uptake also occuring during late afternoon, in both sun and shade fronds. Maximum rates of net CO2 uptake and the nocturnal increase in titratable acidity were lower in shade than in sun fronds. δ13C values of sun and shade fronds were not significantly different, and ranged between-14 and-15‰ suggesting that, in the long term, carbon gain was mainly via CO2 dark fixation. Sun fronds had a higher light compensation point of photosynthesis than shade fronds but the same quantum yield. Yet there was no acclimation of photosynthetic O2 evolution, (measured at 5% CO2) in sun and shade fronds and photosynthesis saturated at between 200 and 400 μmol quanta m-2 s-1. Use of higher light intensities for photosynthesis of sun fronds was probably precluded by low nutrient availability. Total nitrogen was less than 1% of dry weight in fully expanded sun and shade fronds. Exposure of shade fronds to full sunlight for 6 h led to a 60% decline in the quantum yield of photosynthesis and to a decline in variable fluorescence measured at room temperature. Photoinhibition by high light was also observed in Hoya nicholsoniae, a rainforest climber growing in deep shade. This species also exhibited CAM as demonstrated by nocturnal net CO2 uptake, nocturnal acidification and a δ13C value of-14‰. Photosynthetic O2 evolution in this species was saturated at 2.5% of full sunlight. Two species of Dendrobium (Orchidaceae) from sun-exposed sites, one species exhibiting CAM and the other one exhibiting net CO2 uptake exclusively during daytime via conventional C3 photosynthesis, showed similar light response curves and the same quantum yield for photosynthetic O2 evolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384791
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