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  • 1
    Electronic Resource
    Electronic Resource
    An analysis of needle yellowing in healthy and chlorotic Norway spruce(Picea abies) in a forest decline area of the Fichtelgebirge(N.E. Bavaria) (1990)
    Springer
    Trees 4 (1990), S. 55-67 
    Details
    ISSN: 1432-2285
    Keywords: Forest decline ; Needle yellowing ; Chlorophylls ; Carotenoids ; Picea abies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In a forest decline area (Fichtelgebirge, N.E. Bavaria, FRG), annual time courses of chloroplast pigments in both healthy and chlorotic Norway spruce were studied. The seasonal time courses of green and apparently healthy trees did not generally differ from those reported in the literature for spruce trees of other regions. Chlorophyll content increased from May to October, remained relatively constant or declined slightly during the fall and early winter, and finally decreased markedly from March to early May when pigment is at its minimum before bud break. The annual maximal chlorophyll content increased with needle age from the current year's needles to 4-yearold needles. While carotene content reached its highest concentration in August, the xanthophylls did not peak until February or March. Pigment dynamics of chlorotic trees with lower concentrations, corresponded to those of undamaged trees. Chlorophyll deficits resulted from less pigment formation as well as pigment loss during the growing period. Even when the content of total chlorophyll was low, the ratio of chlorophyll a/chlorophyll b remained almost unchanged. In conjunction with the chlorophyll reductions, a decrease in the chlorophyll/carotenoid ratio and an increase in the xanthophyll/carotene ratio occurred. The periods of needle-chlorophyll reduction did not correlate with those periods of highest concentrations of atmospheric sulphur dioxide, the main air pollutant at the stand. However, chlorophyll formation ceased in the older needle age classes of chlorotic trees when the new flush was sprouting, indicating that nutritional deficiencies affect needle yellowing more than possible direct needle damage by air pollutants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00226067
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  • 2
    Electronic Resource
    Electronic Resource
    Changes in photosynthetic capacity, carboxylation efficiency, and CO2 compensation point associated with midday stomatal closure and midday depression of net CO2 exchange of leaves of Quercus suber (1984)
    Springer
    Planta 162 (1984), S. 193-203 
    Details
    ISSN: 1432-2048
    Keywords: Carboxylation efficiency ; Compensation point (CO2) ; Photosynthesis (temperature, humidity) ; Quercus ; Sclerophyll
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The carbon-dioxide response of photosynthesis of leaves of Quercus suber, a sclerophyllous species of the European Mediterranean region, was studied as a function of time of day at the end of the summer dry season in the natural habitat. To examine the response experimentally, a “standard” time course for temperature and humidity, which resembled natural conditions, was imposed on the leaves, and the CO2 pressure external to the leaves on subsequent days was varied. The particular temperature and humidity conditions chosen were those which elicited a strong stomatal closure at midday and the simultaneous depression of net CO2 uptake. Midday depression of CO2 uptake is the result of i) a decrease in CO2-saturated photosynthetic capacity after light saturation is reached in the early morning, ii) a decrease in the initial slope of the CO2 response curve (carboxylation efficiency), and iii) a substantial increase in the CO2 compensation point caused by an increase in leaf temperature and a decrease in humidity. As a consequence of the changes in photosynthesis, the internal leaf CO2 pressure remained essentially constant despite stomatal closure. The effects on capacity, slope, and compensation point were reversed by lowering the temperature and increasing the humidity in the afternoon. Constant internal CO2 may aid in minimizing photoinhibition during stomatal closure at midday. The results are discussed in terms of possible temperature, humidity, and hormonal effects on photosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397440
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  • 3
    Electronic Resource
    Electronic Resource
    Differences in the susceptibility to light stress in two lichens forming a phycosymbiodeme, one partner possessing and one lacking the xanthophyll cycle (1990)
    Springer
    Oecologia 84 (1990), S. 451-456 
    Details
    ISSN: 1432-1939
    Keywords: Carotenoids ; Chlorophyll fluorescence ; Lichens ; Light stress ; Phycosymbiodeme
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effect of high light levels on the two partners of a Pseudocyphellaria phycosymbiodeme (Pseudocyphellaria rufovirescens, with a green phycobiont, and P. murrayi with a blue-green phycobiont), which naturally occurs in deep shade, was examined and found to differ between the partners. Green algae can rapidly accumulate zeaxanthin, which we suggest is involved in photoprotection, through the xanthophyll cycle. Blue-green algae lack this cycle, and P. murrayi did not contain or form any zeaxanthin under our experimental conditions. Upon illumination, the thallus lobes with green algae exhibited strong nonphotochemical fluorescence quenching indicative of the radiationless dissipation of excess excitation energy, whereas thallus lobes with blue-green algae did not possess this capacity. The reduction state of photosystem II was higher by approximately 30% at each PFD beyond the light-limiting range in the blue-green algal partner compared with the green algal partner. Furthermore, a 2-h exposure to high light levels resulted in large reductions in the efficiency of photosynthetic energy conversion which were rapidly reversible in the lichen with green algae, but were long-lasting in the lichen with blue-green algae. Changes in fluorescence characteristics indicated that the cause of the depression in photosynthetic energy conversion was a reversible increase in radiationless dissipation in the green algal partner and “photoinhibitory damage” in the blue-green algal partner. These findings represent further evidence that zeaxanthin is involved in the photoprotective dissipation of excessive excitation energy in photosynthetic membranes. The difference in the capacity for rapid zeaxanthin formation between the two partners of the Pseudocyphellaria phycosymbiodeme may be important in the habitat selection of the two species when living separate from one another.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328159
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  • 4
    Electronic Resource
    Electronic Resource
    Carotenoid composition and metabolism in green and blue-green algal lichens in the field (1993)
    Springer
    Oecologia 94 (1993), S. 576-584 
    Details
    ISSN: 1432-1939
    Keywords: Blue-green algae ; Green algae ; Carotenoids ; Photoprotection ; Zeaxanthin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The carotenoid composition of 33 species of green algal lichens and 5 species of blue-green algal lichens was examined and compared with that of the leaves of higher plants. As in higher plants, green algal lichen species which were found in both shade and full sunlight exhibited higher levels of the carotenoids involved in photoprotective thermal energy dissipation (zeaxanthin as well as the total xanthophyll cycle pool) in the sun than in the shade. This was particularly true when thalli were moist during exposure to high light, or presumably became desiccated in full sunlight. However, the reverse trend in the carotenoid composition of green algal lichens was also observed in those species which were found predominantly either in the shade or in full sunlight. In this case sun-exposed lichens often possessed lower levels of zeaxanthin and of the components of the xanthophyll cycle than lichens which were found in the shade. In contrast to higher plants, the lichens from all habitats exhibited a relatively high ratio of carotenoids to chlorophylls (more characteristic of sun leaves), very low levels of α-carotene (similar to that found in sun leaves), and a level of β-carotene similar to that found in shade leaves. Zeaxanthin, but not the expoxides of the xanthophyll cycle, was also frequently found in blue-green algal lichens. A trend for increasing levels of zeaxanthin with increasing growth light regime was observed inPeltigera rufescens, the species which was found to occur over the widest range of light environments. The level of zeaxanthin per chlorophylla in these blue-green algal lichens was in a range similar to that per chlorophylla+b in green algal lichens. However, zeaxanthin was also absent in one species,Collema cristatum, in full sunlight. Thus, the zeaxanthin content of the blue-green algal lichens can be similar to that of higher plants, or it can be rather dissimilar, as was also the case in the green algal lichen species. The presence of large amounts of ketocarotenoids in blue-green algal lichens is also noteworthy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566975
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of temperature at constant air dew point on leaf carboxylation efficiency and CO2 compensation point of different leaf types (1985)
    Springer
    Planta 166 (1985), S. 81-88 
    Details
    ISSN: 1432-2048
    Keywords: Carboxylation efficiency ; Compensation point (CO2) ; Photosynthesis (temperature, humidity) ; Sclerophyll ; Transpiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of temperature on photosynthesis at constant water-vapor pressure in the air was investigated using two sclerophyll species, Arbutus unedo and Quercus suber, and one mesophytic species, Spinacia oleracea. Photosynthesis and transpiration were measured over a range of temperatures, 20–39° C. The external concentration of CO2 was varied from 340 μbar to near CO2 compensation. The initial slope (carboxylation efficiency, CE) of the photosynthetic response to intercellular CO2 concentration, the CO2 compensation point (Γ), and the extrapolated rate of CO2 released into CO2-free air (R i) were calculated. At an external CO2 concentration of 320–340 μbar CO2, photosynthesis decreased with temperature in all species. The effect of temperature on Γ was similar in all species. While CE in S. oleracea changed little with temperature, CE decreased by 50% in Q. suber as temperature increased from 25 to 34° C. Arbutus unedo also exhibited a decrease in CE at higher temperatures but not as marked as Q. suber. The absolut value of R i increased with temperature in S. oleracea, while changing little or decreasing in the sclerophylls. Variations in Γ and R i of the sclerophyll species are not consistent with greater increase of respiration with temperature in the light in these species compared with S. oleracea.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397389
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