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  • 1
    Digitale Medien
    Digitale Medien
    Leaf anatomical changes in Populus trichocarpa, Quercus rubra, Pseudotsuga menziesii and Pinus ponderosa exposed to enhanced ultraviolet-B radiation (1998)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 104 (1998), S. 0 
    Details
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Leaf anatomical characteristics are important in determining the degree of injury sustained when plants are exposed to natural and enhanced levels of ultraviolet-B (UV-B) radiation (280–320 nm). The degree to which leaf anatomy can adapt to the increasing levels of UV-B radiation reaching the earth's surface is poorly understood in most tree species. We examined four tree species, representing a wide range of leaf anatomical characteristics, to determine responses of leaf area, specific leaf weight, and leaf tissue parameters after exposure to ambient and enhanced levels of UV-B radiation. Seedlings were grown in a greenhouse with photosynthetically active radiation of 39 mol m−2 day−1 and under one of three daily irradiances of biologically effective UV-B radiation (UV-BBE) supplied for 10 h per day: (1) approximate ambient level received at Pullman, Washington on June 21 (1 x ); two times ambient (2 x ), or three times ambient (3 x ). We hypothesized the response of each species to UV-B radiation would be related to inherent anatomical differences. We found that the conifers responded anatomically to nearly an equal degree as the broad-leaved trees, but that different tissues were involved. Populus trichocarpa, an indeterminate broadleaf species, showed significantly thicker palisade parenchyma in recently mature leaves at the 3 x level and in older leaves under the 2 x level. In addition, individual leaf area was generally greater with increased UV-B irradiance. Quercus rubra, a semi-determinate broadleaf species, exhibited significantly thicker palisade parenchyma at the 2 x and 3 x levels as compared to controls. Psuedotsuga menziesii, an evergreen coniferous species with bifacially flattened needles, and Pinus ponderosa, an evergreen coniferous species with a complete hypodermis, showed no significant change in leaf area or specific leaf weight under enhanced UV-B radiation. Epidermal thickness was unchanged in P. menziesii. However, P. ponderosa increased the thickness and number of hypodermal layers produced, presumably decreasing penetration of UV-B radiation into the leaf. We concluded that differences in inherent leaf anatomy of the four species examined are important in the responses to enhanced levels of UV-B radiation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1034/j.1399-3054.1998.1040314.x
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  • 2
    Digitale Medien
    Digitale Medien
    The localization of serine hydroxymethyltransferase in leaves of C3 and C4 species (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 64 (1985), S. 0 
    Details
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: The intracellular distribution of serine hydroxymethyltransferase (EC 2.1.2.1) was studied in young wheat (Triticum aestivum L. cv. Starke II) leaves by fractionation of protoplasts and further purification of peroxisomes and chloroplasts. Essentially all of the activity in wheat leaves was located in the mitochondria. Within the mitochondria the enzyme was mainly in the matrix as shown by centrifugation of sonicated wheat mitochondria. In the C4 plants, Zea mays (L. cv. Earliking), Panicum miliaceum and Panicum maximum (cv. Australia) belonging to different C4 types, serine hydroxymethyltransferase was almost exclusively found in bundle sheath cells. The location of this enzyme in leaves is consistent with its role relative to glycine decarboxylation during photorespiration.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1399-3054.1985.tb01208.x
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  • 3
    Digitale Medien
    Digitale Medien
    Dependence of the Post-Illumination Burst of CO2 on Temperature, Light, CO2, and O2 Concentration in Wheat (Triticum aestivum) (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 46 (1979), S. 0 
    Details
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: The effect of environmental factors on the post-illumination burst of CO2 (PIB) and O2 inhibition of apparent photosynthesis (APS) in wheat (Triticum aestivum L.) was studied in an open gas exchange system utilizing the mathematics of non-steady-state systems. Two components of inhibition by O2 are suggested: one is caused by photorespiration as measured from the maximum rate of the PIB, and the second is direct inhibition as taken as APS2%O2— (APSx%O2+ PIBx%O2) where X is the oxygen concentration.A primary PIB which occurred from 16–28 s after the darkening of the foliage was attributed to photorespiration. No primary PIB was observed at 2% O2. At a CO2 concentration of 100 μ/1 in the atmosphere (about 2.5 μM based on leaf intercellular concentration) and at 30°C and 145 nE/cm2 nE/cm2·s, APS decreased curve-linearly with increasing O2 and reached an O2 compensation point of 560 μM (48% by volume), above which there was a net loss of CO2 in the light. The PIB increased with increasing O2 and became saturated at about 500 μM O2 but decreased above 900 μM O2. Direct inhibition of photosynthesis by O2 increased with increasing O2 concentration.Decreasing CO2 concentration had an effect on the magnitude of the PIB similar to that of increasing O2. At 30°C and 21% O2, the PIB increased with decreasing CO2 down to the CO2 compensation point (I) of 1.4 μM (47 μM/l). Below Γ, both PIB and CO2 evolution into the air in the light (at 21% O2) increased and then decreased at CO2 below 0.8 μM.The ratio of the PIB to APS2% o O2 increased linearly with increasing O2/CO2 ratio where O2 was held constant at 21% and CO2 was varied from 1.4 to 8.5 μM, while direct inhibition of photosynthesis expressed as a proportion of APS2%O2 remained constant over this range. At low CO2 concentration photorespiration as estimated by the PIB is the major part of O2 photosynthesis, while at atmospheric CO2 levels, direct inhibition is the major component.The PIB and APS at 2% and 21% O2 increased hyperbolically with increasing irradiance and all became light-saturated at about 65 nE/cm2 s. The percentage total O2 inhibition of photosynthesis remained constant with increasing irradiance as did the relative contribution of direct O2 inhibition or photorespiration (PIB) to total O2 inhibition.The PIB and APS at 21% O2 had similar temperature optima of 30°C when experimental conditions were adjusted to provide a constant internal O2/CO2 solubility ratio at varying temperatures. However, with a constant external CO2 concentration, the temperature optimum for the PIB shifted upward to 35°C while that for APS at 21% O2 remained at 30°C, which may be due to an increased O2/CO2 concentration in the leaf with increasing temperature.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1399-3054.1979.tb02625.x
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  • 4
    Digitale Medien
    Digitale Medien
    Relationship between photosystem II activity and CO2 fixation in leaves (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 86 (1992), S. 0 
    Details
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: There is now potential to estimate photosystem II (PSII) activity in vivo from chlorophyll fluorescence measurements and thus gauge PSII activity per CO2 fixed. A measure of the quantum yield of photosystem II, ΦII (electron/photon absorbed by PSII), can be obtained in leaves under steady-state conditions in the light using a modulated fluorescence system. The rate of electron transport from PSII equals ΦII times incident light intensity times the fraction of incident light absorbed by PSII. In C4 plants, there is a linear relationship between PSII activity and CO2 fixation, since there are no other major sinks for electrons; thus measurements of quantum yield of PSII may be used to estimate rates of photosynthesis in C4 species. In C3 plants, both CO2 fixation and photorespiration are major sinks for electrons from PSII (a minimum of 4 electrons are required per CO2, or per O2 reacting with RuBP). The rates of PSII activity associated with photosynthesis in C3 plants, based on estimates of the rates of carboxylation (vo) and oxygenation (vo) at various levels of CO2 and O2, largely account for the PSII activity determined from fluorescence measurements. Thus, in C3 plants, the partitioning of electron flow between photosynthesis and photorespiration can be evaluated from analysis of fluorescence and CO2 fixation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1399-3054.1992.tb01328.x
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  • 5
    Digitale Medien
    Digitale Medien
    Salt-induced changes in protein composition in light-grown callus of Mesembryanthemum crystallinum (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 101 (1997), S. 0 
    Details
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: The halophyte Mesembryanthemum crystallinum (ice plant) has been suggested as a model for salt-tolerance in higher plants. To investigate salt-induced changes in polypeptide patterns at the cellular level, a light-grown callus of M. crystallinum with substantial chlorophyll content, was established and the effect of NaCl on the composition of phenol-extracted protein was examined by SDS- and 2D-polyacrylamide gel electrophoresis (PAGE). SDS-PAGE showed the accumulation of five polypeptides with estimated molecular masses of 40, 34, 32, 29 and 14 kDa was enhanced by the addition of 200 mM NaCl to the culture media. The addition of ABA (10 μM) or mannitol (400 mM) did not elicit the same degree of accumulation of these salt-specific proteins. These polypeptides were classified into two groups according to their course of induction: early responsive (40, 34, 29 kDa) and late-responsive (32, 14 kDa) proteins. In addition, two polypeptides (20, 18 kDa) were transiently accumulated during salt treatment. Further separation of soluble proteins by 2-D gel electrophoresis, either isoelectric focusing (IEF) or non-equilibrium pH-gradient electrophoresis (NEPHGE) followed by SDS-PAGE, showed more alterations in accumulation of polypeptides by NaCl than 1-D gel electrophoresis. Overall, levels of more than 30% of basic polypeptides, detected by NEPHGE/SDS-PAGE, were altered by 200 mM NaCl treatment, while only 10% of neutral and acidic polypeptides, detected by IEF/SDS-PAGE, were changed. The enhanced expression of these proteins by salt in cultured cells is most likely related to the cellular responses to salinity, and not to the mechanism of CAM induction in this facultative halophyte.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1399-3054.1997.tb01033.x
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  • 6
    Digitale Medien
    Digitale Medien
    Influence of light intensity during growth on photosynthesis and activity of several key photosynthetic enzymes in a C4 plant (Zea mays) (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 63 (1985), S. 0 
    Details
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Maize (Zea mays L. Hybrid Sweet Corn, Royal Crest), a C4 plant, was grown under different light regimes, after which the rate of photosynthesis and activities of several photosynthetic enzymes (per unit leaf chlorophyll) were measured at different light intensities. Plants were grown outdoors under direct sunlight or 23% of direct sunlight, and in growth chambers at photosynthetic photon flux densities of about 20% and 8% of direct sunlight. The plants grown under direct sunlight had a higher light compensation point than plants grown under lower light. At a light intensity about 25% of direct sunlight, plants from all growth regimes had a similar rate of photosynthesis. Under saturating levels of light the plants grown under direct sunlight had a substantially higher rate of photosynthesis than plants grown under the lower light regimes. The higher photosynthetic capacity in the plants grown under direct sunlight was accompanied by an increased activity of several photosynthetic enzymes and in the amount of the soluble protein in the leaf. Among five photosynthetic enzymes examined, RuBP carboxylase (EC 4.1.1.39) and pyruvate, Pi dikinase (EC 2.7.9.1) were generally just sufficient to account for rates of photosynthesis under saturating light; thus, these may be rate limiting enzymes in C4 photosynthesis. Pyruvate, Pi dikinase and NADP-malate dehydrogenase (EC 1.1.1.82) were the only enzymes examined which were light activated and increased in activity with increasing light intensity. In the low light grown plants the activity of pyruvate, Pi dikinase closely paralleled the photosynthetic rate measured under different light levels. With the plants grown under direct sunlight, as light intensity was increased the activation of pyruvate, Pi dikinase and NADP+-malate dehydrogenase proceeded more rapidly than photosynthesis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1399-3054.1985.tb02819.x
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  • 7
    Digitale Medien
    Digitale Medien
    Action of phenazine methyl sulfate, inhibitors, and uncouplers on the light-induced proton transport by cells ofRhodospirillum rubrum (1970)
    Springer
    The journal of membrane biology 2 (1970), S. 95-107 
    Details
    ISSN: 1432-1424
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary Suspensions of log phase cells ofRhodospirillum rubrum at pH 5.5 show a light-induced decrease in the pH of the medium which is reversed during the subsequent dark period. The velocity and magnitude of the pH change were the same whether the cells were bubbled with air, CO2-free air or N2 during experimentation. The pH response is temperature dependent. Phenazine methyl sulfate (PMS) at concentrations above 0.05mm stimulates the light-induced pH change. PMS at 1mm gives a 2-fold increase in the initial rate upon illumination and a 1.5-fold increase in the total change in pH after 2 min of illumination. The inhibition of the proton transport by 10 μg/ml antimycin A or 20 μm 2-n-heptyl-4-hydroxyquinoline-N-oxide can be partially relieved by PMS. However, inhibition of the light-induced proton transport with 0.5mm 2,4-dinitrophenol or 3 μm carbonylcyanide-m-chlorophenylhydrazone (CCCP) cannot be overcome by addition of PMS. Valinomycin, at a concentration of 3 μm, caused a slight stimulation of the light-induced proton transport in the presence of 200mm KCl. The inhibition of proton transport by 3 μm CCCP was partially relieved with 3 μm valinomycin in the presence of 200mm KCl, but the antibiotic was without effect when the cells were suspended in 200mm NaCl. The results are discussed in terms of current theories of the action of PMS, antimycin A, valinomycin, and uncouplers on the light-induced electron flow and photophosphorylation inR. rubrum.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01869853
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  • 8
    Digitale Medien
    Digitale Medien
    Oxygen inhibition of photosynthesis (1978)
    Springer
    Planta 140 (1978), S. 1-6 
    Details
    ISSN: 1432-2048
    Schlagwort(e): Leaf temperature ; Oxygen (photosynthesis) ; Photosynthesis ; Temperature (photosynthesis) ; Triticum ; Zea
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The effect of leaf temperature, O2 and calculated O2/CO2 solubility ratio in the leaf on the quantum yield of photosynthesis was studied for the C4 species, Zea mays L., and the C3 species, Triticum aestivum L. Over a range of leaf temperatures of 16 to 35° C, the quantum yield of Z. mays was relatively constant and was similar under 1.5 and 21% O2, being ca. 0.059 mol CO2 mol-1 quanta absorbed. Under 1.5% O2 and atmospheric levels of CO2, the quantum yield of T. aestivum was relatively constant (0.083 mol CO2 mol-1 quanta absorbed) at leaf temperatures from 15 to 35° C. Atmospheric levels of O2 (21%) reduced the quantum yield of photosynthesis in T. aestivum and as leaf temperature increased, the quantum yield decreased from 0.062 at 15°C to 0.046 mol CO2 mol-1 quanta absorbed at 35°C. Increasing temperature decreases the solubility of CO2 relatively more than the solubility of O2, resulting in an increased solubility ratio of O2/CO2. Experimentally manipulating the atmospheric levels of O2 or CO2 to maintain a near-constant solubility ratio of O2/CO2 at varying leaf temperatures largely prevented the temperature-dependent decrease in quantum yield in t. aestivum. Thus, the decrease in quantum yield with increasing leaf temperature in C3 species may be largely caused by a temperaturedependent change in the solubility ratio of O2/CO2.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00389372
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  • 9
    Digitale Medien
    Digitale Medien
    Photosynthesis in enzymatically isolated leaf cells from the CAM plant Sedum telephium L. (1978)
    Springer
    Planta 141 (1978), S. 59-63 
    Details
    ISSN: 1432-2048
    Schlagwort(e): Crassulacean acid metabolism (CAM) ; Oxygen evolution (photosynthesis) ; Photosynthesis ; Sedum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A technique has been developed for the enzymatic isolation of leaf cells from the Crassulacean acid-metabolism plant Sedum telephium. The cells exhibited high activity in both 14CO2 incorporation (30–70 μmol CO2 mg-1 chlorophyll h-1) and O2 evolution in the presence of bicarbonate (60–110 μmol O2 mg-1 chlorophyll h-1). Half-maximum saturation of 14CO2 incorporation occurred at a bicarbonate concentration of ca. 2 mM (20 μM CO2) at pH 8.4 and 30°C. Two types of light-dependent O2 evolution are reported: O2 evolution in the absence of exogenously supplied bicarbonate (endogenous O2 evolution), and bicarbonate-stimulated O2 evolution. Oxygen evolution in the presence of approximately ambient concentrations of CO2 appeared to be a combination of the endogenous O2 evolution and O2 evolution from fixation of the exogenously supplied CO2.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00387745
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  • 10
    Digitale Medien
    Digitale Medien
    The influence of inorganic phosphate on photosynthesis in intact chloroplasts from Mesembryanthemum crystallinum L. plants exhibiting C3 photosynthesis or crassulacean acid metabolism (1983)
    Springer
    Planta 159 (1983), S. 97-104 
    Details
    ISSN: 1432-2048
    Schlagwort(e): Crassulacean acid metabolism ; Mesembryanthemum ; Chloroplast, isolated ; Photosynthesis (O2 evolution, CO2 fixation)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Intact chloroplasts were obtained from mesophyll protoplasts isolated from Mesembryanthemum crystallinum in the C3 or Crassulacean acid metabolism (CAM) photosynthetic mode, and examined for the influence of inorganic phosphate (Pi) on aspects of bicarbonate-dependent O2 evolution and CO2 fixation. While the chloroplasts from both modes responded similarly to varying Pi, some features appear typical of chloroplasts from species capable of CAM, including a relatively high capacity for photosynthesis in the absence of Pi, a short induction period, and resistance to inhibition of photosynthesis by high levels of Pi. In the absence of Pi the chloroplasts retained 75–85% of the 14CO2 fixed and the total export of dihydroxyacetone phosphate was low compared with the rate of photosynthesis. In CAM plants the ability to conduct photosynthesis and retain most of the fixed carbon in the chloroplasts at low external Pi concentrations may enable storage of carbohydrates which are essential for providing a carbon source for the nocturnal synthesis of malic acid. At high external Pi concentrations (e.g. 10 25 mM), the amount of total dihydroxyacetone phosphate exported to the assay medium relative to the rate of photosynthesis was high while the products of 14CO2 fixation were largely retained in the chloroplasts which indicates starch degradation is occurring at high Pi levels. Starch degradation normally occurs in CAM plants in the dark; high levels of Pi may induce starch degradation in the light which has the effect of limiting export of the immediate products of photosynthesis and thus the degree of Pi inhibition of photosynthesis with the isolated chloroplast.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00392978
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