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  • 1
    ISSN: 1432-2048
    Keywords: Cell water status ; Cuticle ; Gas exchange ; Humidity (vapor-pressure difference) ; Stomatal movement ; Tradescantia (stomatal movement) ; Water stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Turgor, and osmotic and water potentials of subsidiary cells, epidermal cells and mesophyll cells were measured with a pressure probe and a nanoliter osmometer in intact transpiring leaves of Tradescantia virginiana L. Xylem water potential was manipulated by changing air humidity, light, and water supply. In a transpiring leaf the water potential of mesophyll cells was lower, but turgor was higher, than in cells surrounding the stomatal cavity owing to the presence of a cuticle layer which covers the internal surface of subsidiary and guard cells. Cuticular transpiration from the outer leaf surface was negligibly small. When stomata closed in dry air, transpiration decreased despite an increasing vapor-pressure difference between leaf and air, and the water potential of subsidiary cells dropped to the level of the water potential in mesophyll cells. We suggest that the observed decrease of transpiration at increasing vapor-pressure difference can be attributed to a shortage of water supply to the guard cells from subsidiary cells, causing turgor to decrease in the former more than in the latter. The leafs internal cuticle appears to play a special role in channelling the internal water flow during a water shortage.
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  • 2
    ISSN: 1432-1939
    Keywords: Carbon isotope composition ; Crassulacean acid metabolism (CAM) ; Ecophysiology ; Kalanchoë ; Madagascar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The carbon isotope compositions of samples of Kalanchoë species collected at the natural stands in Madagascar were determined. The results suggest that all species of the genus Kalanchoë are capable of crassulacean acid metabolism. The observed δ13C values cover the whole range from −10 to −30‰. This high diversity of the δ13C values was found among the species of the genus as well as, in certain cases, within a single species. This suggest that the CAM patterns in Kalanchoë are generally very flexible. The δ13C values show a clear correlation with the climate of the habitats from where the samples derived. Values indicative of CO2 fixation taking place exclusively during the night were found in the dry regions of Madagascar, whereas δ13C values indicative of mixed CO2 fixation during night and day or of CO2 fixation entirely during the day are distributed in the humid zones.
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  • 3
    ISSN: 1432-1939
    Keywords: Crassulacean acid metabolism ; Mesembryanthemum ; Reproduction ; Water stress-δ13C ; value
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mesembryanthemum crystallinum L., an inducible crassulacean acid metabolism (CAM) plant, was grown for approximately 5 weeks following germination in well-watered, non-saline soil in a controlled-environment chamber. During this time, plants were characterized by C3 photosynthetic carbon metabolism. After the initial 5 weeks, CAM was induced by a combination of high soil salinity and reduced soil water content. One group of plants was allowed to engage in CAM by being continuously exposed to normal CO2-containing air (about 350–400 ppm). A second group of plants was deprived of ambient CO2 each night (12 h dark period) until completion of their life cycle, thereby minimizing potential carbon gain via dark CO2 fixation. The capacity to express CAM under conditions of drought and salinity stress markedly improved reproductive success: plants kept in normal CO2-containing air produced about 10 times more seeds than plants kept in CO2-free air during dark periods. Seeds from plants deprived of ambient CO2 overnight had more negative δ13C values than seeds from plants kept in normal air.
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  • 4
    ISSN: 1432-2285
    Keywords: Abies alba ; Abscisic acid ; Damage ; Gas chromatography ; Needles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The amount of abscisic acid (ABA) in needles of silver fir from a natural location was investigated with regard to position in the crown, damage, seasonal variation, and needle age. Because of problems of quantification of ABA in coniferous needles, which contain numerous secondary plant products, a method for reliable determination of both isomers cis-trans-ABA (c-ABA) and transtrans-ABA (t-ABA) was developed. By means of gas chromatography (GC) using an electron capture detector (BCD) and a programmed temperature vaporizer (PTV) injector complete separation of both compounds was achieved. Two different pairs of fir were investigated — in each case a damaged and a healthy tree. Needles from both trees from the first and the second pair collected in September contained 500–1100 ng c-ABA/g fresh weight (FW), and the concentrations of t-ABA varied from 400 to 700 ng/g FW. Investigations from the second pair show highest amounts of 2900 ng/g Fw c-ABA and 1800 ng/g FW of t-ABA in May and June. For the first pair a higher c-ABA content was found in needles from the top of the crown than in those from the middle and the base. This difference could not be confirmed in the analysis of the second pair. Because of the strong natural deviation no statistically significant difference between the healthy and the damaged tree was found. The first pair of firs examined showed a higher t-ABA concentration than the second one. In this case the highest amount was found in the top of the crown. Methodical mistakes during the clean-up procedure and in quantification by gas chromatography could be excluded. The presence of c- and t-ABA in the purified extract was corroborated by mass spectrometry. With regard to the seasonal variation both isomers of ABA show an unequivocal trend. The maximum concentration is achieved in May to June, whereas the content is minimal in August/September. In any case the level of t-ABA is lower than that of c-ABA. No correlation between the amount of ABA and the needle age could be established.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Trees 6 (1992), S. 32-36 
    ISSN: 1432-2285
    Keywords: Abies ; Cuticle ; Monoterpene ; Octanol/water partition coefficient ; Picea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Cuticle/water partition coefficients (Kc/w) for d-limonene, α-pinene and β-pinene were determined by an extrapolation and a desorption method. The sorption experiments were carried out with isolated angiosperm and gymnosperm cuticles and with [14C]-labelled monoterpenes, which were obtained biosynthetically. Both methods were suitable for the determination of the Kc/w of volatile hydrophobic compounds. For the angiosperm cuticles the partition coefficients are of the order of 104, which indicates a high accumulation of monoterpenes in the cuticle. The values of the conifer cuticles of Picea abies (L.) Karst. and Abies alba Mill., however, are lower due to their high lignin content. This is proved by the increase of the partition coefficients after removal of polar and phenolic components. The Kc/w can be estimated with good accuracy from the octanol/water partition coefficient, which was determined experimentally.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Trees 6 (1992), S. 172-177 
    ISSN: 1432-2285
    Keywords: Citrus ; Cuticle ; Diffusion coefficient ; Limonene ; Monoterpene ; Ozone ; Permeability coefficient ; Permeation ; α-Pinene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Permeation parameters of isolated cuticular membranes of Citrus aurantium L. for gaseous monoterpenes were determined by an isostatic system. For α-pinene and d-limonene permeability coefficients range from 4.3 × 10−11 m−2 s−1 to 7.3 × 10−11 m−2 s−1. These values can be compared to that measured for benzene gas at the cuticle of Citrus. The permeability coefficients of the two monoterpenes did not differ significantly, in contrast to their diffusioin coefficients. The diffusion coefficient values are 3.7 × 10−15 m−2 s−1 for limonene and 15.5 × 10−15 m−2 s−1 for α-pinene. The reason for this difference is still unclear. A dependence of the permeation parameters on the direction of the monoterpene transport could not be observed. Moreover, there are some indications that, in spite of its heterogeneous character, the cuticular membrane of Citrus is homogeneous in respect to the transport of small gaseous molecules. An exposure to environmentally relevant ozone concentrations for 6 months did not change the permeation characteristics of the membrane. Due to the high variability of the samples only a tendency towards higher permeability coefficients of cuticles treated with 80 ppb ozone was observed. This may be attributed to a reduced tension of the membrane caused by chain fractions.
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  • 7
    ISSN: 1432-2285
    Keywords: Robinia pseudoacacia ; Heartwood ; Flavonols ; Starch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The distributions of reserve carbohydrates and of three dominant heartwood extractives were determined in the trunkwood of Robinia pseudoacacia L. The trees were cut at different times of the year (September, November, January, and April). With the exception of the tree felled in January, all trunks exhibited highest contents of nonstructural storage carbohydrates (glucose, fructose, sucrose, and starch) in the youngest, outermost sapwood zone. With increasing depth of the trunk, the levels of carbohydrates decreased. At the sapwood-heartwood transition zone, only trace amounts of nonstructural carbohydrates were present. The heartwood itself contained no storage material. The wood zones of different ages of the trees cut in September, November, and January exhibited glucose/fructose ratios of approximately 1. In April, however, there was a shift to glucose. In the youngest sapwood the amounts of soluble sugars were higher in the earlythan in the latewood. Older zones of the sapwood and the sap-wood-heartwood transition zone showed the opposite behaviour. Three main wood extractives of Robinia were characterized and quantified: the flavanonol dihydrorobinetin (DHR), the flavonol robinetin (ROB) and a hydroxycinnamic acid derivative (HCA). Only DHR was present — in very low amounts — in the younger sapwood of all trunks investigated. Higher amounts (〉1 μmol/g dry weight) of this compound and the HCA were present in the sapwood-heartwood transition zone. DHR augmented within the heartwood up to a more or less constant level. HCA increased towards the heartwood and decreased again in the inner heartwood parts. ROB appeared in the innermost parts of the sapwood-heartwood transition zone and reached maximum values in older parts of the heart-wood. The results indicate that starch is hydrolyzed at the sapwood-heartwood boundary and thus represents a primary major source of hydroxycinnamic acid and flavonoid synthesis.
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  • 8
    Publication Date: 1991-12-01
    Print ISSN: 0032-0935
    Electronic ISSN: 1432-2048
    Topics: Biology
    Published by Springer
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  • 9
    Publication Date: 1991-11-01
    Print ISSN: 0029-8549
    Electronic ISSN: 1432-1939
    Topics: Biology
    Published by Springer
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  • 10
    Publication Date: 1992-01-01
    Print ISSN: 0029-8549
    Electronic ISSN: 1432-1939
    Topics: Biology
    Published by Springer
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