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  • 1
    Electronic Resource
    Electronic Resource
    Comparative measurements of chlorophyll a fluorescence, acid accumulation and gas exchange in exposed and shaded plants of Clusia minor L. and Clusia multiflora H. B. K. in the field (1997)
    Springer
    Trees 11 (1997), S. 240-247 
    Details
    ISSN: 0931-1890
    Keywords: Key words Chlorophyll a fluorescence ; Clusia ; Crassulacean acid metabolism (CAM) ; Electron transport rate through photosystem II ; Malate decarboxylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Changes in chlorophyll a fluorescence during the day and diurnal-changes of net CO2-exchange and organic acid contents were determined in two species of the genus Clusia during the dry season in Venezuela. The investigations included plants of the C3/CAM intermediate species Clusia minor and the C3 species C. multiflora growing at exposed and shaded sites. Both species showed a C3 pattern of net CO2-exchange at the exposed site. In the shade under extreme drought stress C. minor showed a weak expression of CAM without CO2-uptake during the afternoon (phase IV of CAM). C. multiflora growing in the shade exhibited a C3-pattern of net CO2-exchange and a small but significant nocturnal accumulation of citrate. Shaded plants of C. minor were able to double their light utilisation for electron transport and to reduce non-photochemical quenching during phase III compared to phase II of CAM. Furthermore, increase of electron transport rate through photosystem II in phase III of CAM is correlated to decarboxylation of malate. At the exposed site C. multiflora was less negatively affected by high PPFD than C. minor. This was shown by a lower reduction of potential electron quantum yield (Fv/Fm) and higher light utilisation of electron transport of C. multiflora compared to C. minor. At the exposed site C. minor did not make use of the CAM option to increase light utilisation of electron transport and to reduce non-photochemical quenching as did the plants growing in the shade.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00009670
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  • 2
    Electronic Resource
    Electronic Resource
    Cyanobacterial Tintenstrich Communities and their Ecology (1997)
    Springer
    Naturwissenschaften 84 (1997), S. 526-534 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Notes: Tintenstrich communities receive their name from the black strips on rocks, which are particularly spectacular on the background of white limestone and dolomite. They are dominated by cyanobacteria, green photosynthesizing procaryotes. However, cyanobacterial crusts are ubiquitous and much more widespread. On bare substratum on walls and rocks in temperate, arid, and tropical zones they are subject to severe stress by insolation, heat, and either too little or too much water. An array of ecophysiological traits allow them to endure this multifactorial stress. Particular features of their photosynthetic membranes may facilitate dissipation of surplus photosynthetically active radiation; special sun-screen pigments protect them from UV radiation, they are desiccation tolerant, concentrate inorganic carbon for photosynthetic fixation, and assimilate atmospheric dinitrogen. With their own success on bare substratum they become pioneers for other organisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001140050439
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  • 3
    Electronic Resource
    Electronic Resource
    Generation of rhythmic and arrhythmic behaviour of Crassulacean acid metabolism in Kalanchoë daigremontiana under continuous light by varying the irradiance or temperature: Measurements in vivo and model simulations (1996)
    Springer
    Planta 198 (1996), S. 110-117 
    Details
    ISSN: 1432-2048
    Keywords: Circadian rhythm ; Crassulacean acid metabolism ; Kalanchoe ; Model simulations ; Phase setting ; Tonoplast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Leaves of Kalanchoë daigremontiana Hamet et Perr. at a photon flux density (PFD) above 220 μmol·m−2s−1 (400–700 nm) or at leaf temperatures above 27.0 °C showed a rapid loss of rhythmicity, and a more or less pronounced damping-out of the endogenous circadian rhythm of CO2 exchange under continuous illumination. This rhythm was reinitiated after reduction of the PFD by 90–120 μmol·m−2·s−1 or reduction of leaf temperature by 3.5–11.0 °C under otherwise unchanged external conditions. The reduction in the magnitude of the external control parameter of the Crassulacean acid metabolism (CAM) rhythm (i.e. PFD or leaf temperature) set the phase of the new rhythm. The maxima of CO2 uptake occurred about 5, 28, 51, 75 h after the reduction. Simulations with a CAM model under comparable conditions showed a similar behaviour. The influence of temperature on the endogenous CAM rhythm observed in K. daigremontiana in vivo could be simulated by incorporating into the model temperature-dependent switch modes for passive efflux of malate from the vacuole to the cytoplasm. Thus, the model indicates that tonoplast function plays an important role in regulation of the endogenous CAM rhythm in K. daigremontiana.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197593
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  • 4
    Electronic Resource
    Electronic Resource
    Temperature profiles for the expression of endogenous rhythmicity and arrhythmicity of CO2 exchange in the CAM plant Kalanchoë daigremontiana can be shifted by slow temperature changes (1998)
    Springer
    Planta 207 (1998), S. 76-82 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Crassulacean acid metabolism ; Circadian rhythm ; Kalanchoë ; Photosynthesis oscillation ; Synchronizer (“zeitgeber”) ; Temperature gradient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The crassulacean acid metabolism (CAM) plant Kalanchoë daigremontiana Hamet et Perrier de la Bâthie shows an endogenous circadian rhythm of net CO2 exchange (J CO2 ) under constant conditions in continuous light. Previous studies have shown, however, that above a certain threshold temperature J CO2 changes from rhythmic to arrhythmic behaviour and that this is reversible when the temperature is lowered again. It is now demonstrated here, that this re-initiation of rhythmic J CO2 from arrhythmicity needs a sufficiently strong temperature signal as defined by its abruptness. Rhythmicity reappears only if the temperature is reduced rather rapidly. If the temperature is reduced slowly then arrhythmicity is retained even at a low temperature level which normally would allow rhythmicity. Under these circumstances, however, a distinct temperature increase followed by an abrupt temperature decrease immediately elicits regular oscillations of J CO2 at this lower temperature. We suggest that the strong temperature signals function as a definite synchronizer (“zeitgeber”) which synchronizes different cells and/or different leaf areas which remain desynchronized after application of only slow temperature changes. This is further supported by Fourier transform analyses, revealing a harmonic structure of the superficially arrhythmic time series of J CO2 after application of slow temperature reductions. This conclusion adds a spatial dimension to the otherwise purely time-dependent rhythmicity and arrhythmicity of J CO2 in CAM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050457
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of light levels on daily patterns of chlorophyll fluorescence and organic acid accumulation in the tropical CAM treeClusia hilariana (1996)
    Springer
    Trees 10 (1996), S. 359-365 
    Details
    ISSN: 1432-2285
    Keywords: Chlorophylla fluorescence quenching ; Citric acid ; Malic acid ; Photochemistry ; Photosynthetic electron transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Sandy plains are characteristic of the coastal region of Brazil. We investigated the diel patterns of changes in organic acid levels, leaf conductance and chlorophylla fluorescence for sun-exposed and shaded plants ofClusia hilariana, one of the dominant woody species in the sandy coastal plains of northern Rio de Janeiro state. Both exposed and shaded plants showed a typical CAM pattern with considerable diel oscillations in organic acid levels. The degradation of both malic and citric acids during the midday stomatal closure period could lead to potential CO2 fixation rates of 28 μmol m-2 s-1 in exposed leaves. Moreover, exposed leaves exhibited large increases in total non-photochemical quenching (qN) accompanied by a substantial decrease in effective quantum yield during the course of the day. However, these potential high rates of CO2 fixation and the increases inqn of exposed plants were not enough to maintain the primary electron acceptor of photosystem II (qA) in a low reduction state, similar to that of shaded plants. As a result, there was a moderate increase in the reduction state of qA throughout the day. Most of the decline in photochemical efficiency of exposed leaves ofC. hilariana was reversible, as evidenced by the high levels of pre-dawn potential quantum yields (Fv/Fm) and their rapid recovery after sunset. However, the depletion of the organic acid pool in the afternoon resulted in an accentuated subsequent drop in Fv/Fm, suggesting that prolonged periods of water stress accompanied by high irradiance levels may expose plants ofC. hilariana in unprotected habitats to the danger of photoinhibition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02185639
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