Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    The CO2-concentrating mechanism is absent in the green alga Coccomyxa: a comparative study of photosynthetic CO2 and light responses of Coccomyxa, Chlamydomonas reinhardtii and barley protoplasts (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: Photosynthesis was characterized for the unicellular green alga Coccomyxa sp., grown at low inorganic carbon (Ci) concentrations, and compared with Chlamydomonas reinhardtii, which had been grown so that the CO2 concentrating mechanism (CCM) was expressed, and with protoplasts isolated from the C3 plant barley (Hordeum vulgare). Chlamydomonas had a significantly higher Ci-use efficiency of photosynthesis, with an initial slope of the Ci-response curve of 0.7 mol(gChl)−1 h−1 mmol Cim−3)−1, as compared to 0.3 and 0.23 mol(gChl)−1 h−1 (mmol Cim−3)−1 for Coccomyxa and barley, respectively. The affinity for Ci was also higher in Chlamydomonas, as the half maximum rate of photosynthesis [K0.5 (Ci)] was reached at 0.18 mol m−3, as compared to 0.30 and 0.45 mol m−3 for Coccomyxa and barley, respectively. Ethoxyzolamide (EZ), an inhibitor of the enzyme carbonic anhydrase (CA) and the CCM, caused a 17-fold decrease in the initial slope of the photosynthetic Cj-response curve in Chlamydomonas, but only a 1.5- to two-fold decrease in Coccomyxa and barley. The photosynthetic light-response curve showed further similarities between barley and Coccomyxa. The rate of bending of the curve, described by the convexity parameter, was 0.99 (sharp bending) and 0.81–0.83 (gradual bending) for cells grown under low and high light, respectively. In contrast, the maximum convexity of Chlamydomonas was 0.85. The intrinsically lower convexity of Chlamydomonas is suggested to result from the diversion of electron transport from carbon fixation to the CCM. Taken together, these results suggest that Coccomyxa does not possess a CCM and due to this apparent lack of a CCM, we propose that Coccomyxa is a better cell model system for studying C3 plant photosynthesis than many algae currently used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1994.tb00266.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Causes of variation in cold hardiness among fast-growing willows (Salix spp.) with particular reference to their inherent rates of cold hardening (2002)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 25 (2002), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Causes of variation in cold hardiness in the autumn were assessed among closely related, fast-growing clones of willow of northern/continental and southern/maritime origins, under controlled regimes and natural conditions. Cold hardiness was assessed by controlled freezing followed by injury analysis, based on measurements of chlorophyll fluorescence (stems) and electrolyte leakage (leaves). During growth at a given temperature, the cold hardiness of the clones' stems was negatively correlated with their rate of growth. This apparently phenotypic variation was independent of temperature and, hence, the absolute growth rate. At later stages, cold hardiness of stems varied mainly with respect to genetic differences in the timing and rate of cold hardening. Cold hardening began up to 7 weeks earlier in northern/continental clones, and their rates of hardening in cool temperature regimes were up to three times higher than in southern/maritime clones. Ranking of clones with respect to rates was essentially the same whether natural or abrupt reductions of day length were used to trigger cold hardening. Results closely agreed with those of a previous field trial. Comparisons of rates at cool and warm temperatures suggest that cold hardening became increasingly dependent on cool temperatures with time. Increasing sucrose-to-glucose ratios, and especially dry-to-fresh weight ratios, paralleled early cold hardening. Before leaves were shed in the autumn they underwent cold hardening in parallel with stems, eventually allowing them to tolerate temperatures down to −10 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2002.00902.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Relationship between respiratory depletion of sugars and loss of cold hardiness in coniferous seedlings over-wintering at raised temperatures: indications of different sensitivities of spruce and pine (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 20 (1997), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Long-term effects of elevated winter temperatures on cold hardiness were investigated for Norway spruce (Picea abies L. Karst.), lodgepole pine (Pinus contorta Dougl.) and Scots pine (Pinus sylvestris L.). Two-year-old seedlings with the same pre-history of growth and cold hardening in the field were maintained from early December to late March at two field sites in northern Sweden and in a cold room. The temperatures at these locations averaged –13·5, –8·9 and 5·5°C, respectively. Following treatments, carbohydrate contents and cold tolerances were assessed. Needle respiration was also analysed during the 5·5°C treatment. Cold tolerance of lodgepole pine and Scots pine was much reduced following the 5·5°C treatment. Cold tolerance was somewhat reduced in lodgepole pine following the –8·9 °C treatment, but was essentially maintained in spruce throughout all treatments. The cold tolerance of needles was strongly correlated with their soluble sugar contents. Spruce maintained cold hardiness by having larger reserves of sugars and lower rates of respiration which decreased more rapidly as sugars were depleted. Tolerance of lodgepole pine to frost desiccation was also much reduced following the 5·5°C treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1997.d01-56.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Evaluation of a technique for the measurement of chlorophyll fluorescence from leaves exposed to continuous white light (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 8 (1985), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract An instrument for the generation and measurement of modulated chlorophyll fluorescence signals from leaves exposed to continuous, highintensity white light is described. Modulated fluorescence is generated in the leaf by pulsed diodes emitting low-intensity yellow radiation and is detected with a photodiode whose output is fed to an amplifier locked in to the frequency of the lightemitting diodes. Comparisons are made between the modulated fluorescence signals measured with this instrument and the continuous fluorescence signals emitted from dark-adapted leaf tissue and isolated thylakoids when photosynthetic activity is induced by exposure to a range of intensities of continuous broad-band, blue-green light. The modulated fluorescence signals were similar to the continuous fluorescence signals, but they were not always identical. The small differences between the two signals are mainly attributable to differences in the populations of chloroplasts being monitored in the two measurements as a result of differential penetration of the modulated and actinic light sources into the sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1985.tb01691.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Photosynthetic light-response curves (1993)
    Springer
    Planta 189 (1993), S. 191-200 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll fluorescence ; Eucalyptus ; Leaf (orientation, light-absorption profile) ; Photoinhibition ; Photosynthetic capacity (intraleaf gradient)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Gradients in photosynthetic capacity through the leaf affect the shape of the irradiance-response curve. These gradients in photosynthetic capacity were manipulated by restraining leaves in different orientations. The shape or curvature of the light-response curve can be defined by Θ, where Θ=0 is a rectangular hyperbola and Θ=1 is a Blackman curve. Horizontal leaves had the highest Θ values when their adaxial (top) surface was illuminated and lowest Θ value when their abaxial (bottom) surface was illuminated. Vertical leaves had intermediate Θ values that were similar for illumination from either direction, indicating that both surfaces had similar photosynthetic capacities. The photosynthetic capacity near each surface was probed by measuring the resistance to photoinhibition by 2000 μmol quanta · m −2·s −1 for 2 h followed by 15 min dark relaxation. Resistance to photoinhibition was consistent with the amount of direct sunlight exposure during growth. By measuring three light-response curves for a given leaf, illuminating the leaf from either the adaxial or abaxial surface or with the adaxial and abaxial surfaces illiminated equally, it was possible to infer gradients in the light absorption and photosynthetic capacity of the leaf using a ten-layer model. The gradient in light absorption was not as steep as expected and the photosynthetic capacity declined from the adaxial surface but increased again approaching the abaxial surface, the increase being more pronounced in vertical leaves. The modelled gradients were qualitatively similar for dorsiventral and isolateral leaves. The gradients in light absorption and photosynthetic capacity were not identical and this results (1) in curvilinear relationships between the quantum efficiency of PSII determined by chlorophyll fluorescence and the quantum efficiency of leaf photosynthesis and (2) in light-response curves that slowly reach saturation rather than being abruptly truncated. The Θ value for the photosynthetic light-response curve will remain a parameter that has to be derived empirically, in contrast to the maximum quantum yield and photosynthetic capacity. The curvature factor, Θ, depends on CO2 partial pressure and the interplay between the gradients in light absorption and photosynthetic capacity through the leaf which can change depending on the light environment during growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195076
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Photosynthetic light-response curves (1993)
    Springer
    Planta 189 (1993), S. 182-190 
    Details
    ISSN: 1432-2048
    Keywords: Acclimation (light) ; Carbon dioxide (inhibition of O2 evolution) ; Chlorophyll fluorescence ; Eucalytpus ; Light absorption (intraleaf gradient) ; Photosynthesis (light response)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The shapes of photosynthetic light-response curves for leaves of Eucalyptus maculata (Hook) and E. pauciflora (Sieber ex Sprengel) were examined. Three different methods were used to measure photosynthesis: CO2 and H2O-vapour exchange, O2 evolution at a 5-kPa CO2 partial pressure, and chlorophyll fluorescence. The three methods were compared and gave good agreement when measured under equivalent conditions. However, O2 evolution was inhibited by high CO2 partial pressures. A non-rectangular hyperbolic curve has been used widely to describe photosynthetic light-response curves. It has three variables which define the maximum quantum yield (photosynthetic rate divided by absorbed irradiance at very low irradiances), the maximum capacity and the curvature (Θ). We found that Θ was affected by the CO2 partial pressure, declining to a minimum of about 0.6 as CO2 partial pressure increased to 100 Pa. Further increases in the CO2 partial pressure began to inhibit the rate of O2 evolution at 2000 μmol quanta · m−2·−1 and Θ increased back to 0.95 by 5 kPa CO2 partial pressure. At low irradiances, photosynthesis is limited by the rate of electron transport while at high irradiances, photosynthesis is frequently limited by the activity of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco). The dependence of Θ on CO2 partial pressure arises because the transition between limitations changes as a function of the CO2 partial pressure. The light-response curve is truncated by the transition to a Rubisco limitation and the lower the irradiance at the transition, the higher the value of Θ. There is a gradient in light absorption through the leaf which influences the photosynthetic capacity of different layers within the leaf. The gradient in photosynthetic capacity can be demonstrated by the fact that the shape of the light-response curve changes when the leaf is illuminated unilaterally onto either the adaxial or abaxial surface. We compared two Eucalyptus species which had either isolateral or dorsiventral leaf anatomy. Leaves were able to reverse completely the gradients in photosynthetic capacity following inversion of the leaves for a week, irrespective of their anatomy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195075
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Effects of drought on photosynthesis, chlorophyll fluorescence and photoinhibition susceptibility in intact willow leaves (1985)
    Springer
    Planta 166 (1985), S. 380-388 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll fluorescence ; Photoinhibition ; Photosynthesis (drought effect) ; Salix ; Water stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plants from clonal cuttings of Salix sp. were subjected to a drying cycle of 10 d in a controlled environment. Gas exchange and fluorescence emission were measured on attached leaves. The light-saturated photosynthetic CO2 uptake became progressively inhibited with decreased leaf water potential both at high, and especially, at low intercellular CO2 pressure. The maximal quantum yield of CO2 uptake was more resistant. The inhibition of light-saturated CO2 uptake at leaf water potentials around-10 bar, measured at a natural ambient CO2 concentration, was equally attributable to stomatal and non-stomatal factors, but the further inhibition below this water-stress level was caused solely by non-stomatal factors. The kinetics of fluorescence emission was changed at severe water stress; the slow secondary oscillations of the induction curve were attenuated, and this probably indicates perturbations in the carbon reduction cycle. The influence of light level during the drought period was also studied. Provided the leaves were properly light-acclimated, drought at high and low light levels produced essentially the same effects on photosynthesis. However, low-light-acclimated leaves became more susceptible to photoinhibitory treatment under severe water stress, as compared with well-watered conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00401176
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Suboptimal nitrogen status sensitizes the photosynthetic apparatus in willow leaves to long term but not short term water stress (1988)
    Springer
    Photosynthesis research 18 (1988), S. 263-275 
    Details
    ISSN: 1573-5079
    Keywords: carboxylation efficiency ; photosynthesis ; Rubisco ; water stress ; willow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The response to drought was compared for willow plants of optimal leaf nitrogen content (100 N) and those of 86% of this content (86 N). Gas exchange measurements revealed that the carboxylation efficiency (CE) of photosynthesis was more sensitive to drought than the photosynthetic capacity in both N regimes. Since the leaf content of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) was found to be much more resistant it is suggested that a decreased specific activity of Rubisco underlies the decreased CE. Although the rate of water consumption was the same for 86 N and 100 N plants the photosynthetic apparatus responded much more rapidly in the 86 N leaves. This increased sensitivity of 86 N leaves was not due to accelerated senescence as judged by comparison with parallel plants subjected to discontinued fertilization; the two categories of treatments resulted in the same loss of leaf nitrogen and Rubisco but drought induced a much more rapid photosynthetic depression. In contrast to the drought situation, 86 N and 100 N plants behaved similarly when compared under short term water stress. First, when single attached leaves were exposed to a sudden drop in air humidity the capacity of CO2 uptake in both N regimes decreased about 20% over 10 min while the leaf water potential remained high. Second, in freely transpiring leaf discs cut from 86 N and 100 N leaves the same relationship between capacity of O2 evolution and extent of dehydration was observed. The possible mechanisms underlying the increased susceptibility of 86 N leaves to drought is discussed; the water status of the roots not the leaves is suggested to be the determining factor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00034831
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...