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  • 1
    Electronic Resource
    Electronic Resource
    Photoperiod control of the initial phase of frost hardiness development in Pinus radiata (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 12 (1989), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. The development of frost hardiness in Pinus radiata was investigated to establish whether there is quantitative relationship between photoperiod and the hardening process. Three controlled environment experiments were carried out. In the first, seedlings were exposed to a photoperiod that shortened from 13 h at a rate of 3 min d−1 to 9.5 h. At intervals, the photoperiod was either held constant or lengthened. In the second experiment, seedlings were exposed to one of five constant photoperiods between 9 and 12 h for up to 90 d. In the third, seedlings were exposed to photoperiods shortening at rates of 1 or 5 min d−1. Frost hardiness was also measured during the natural photoperiod-controlled stage of hardening in outdoor-grown seedlings. Frost hardiness developed at a constant rate in response to a shortening photoperiod once it had declined to about 12 h. This rate was consistent with the hardening rate that occurred in outdoor-grown seedlings. Hardening stopped when the photoperiod became constant, indicating a tight coupling between changes in photoperiod and hardiness development. When the photoperiod was held constant, the extent of frost hardiness was directly dependent on the photoperiod but the rate of hardening was apparently independent of the length of photoperiod. However, the rate of hardening was dependent on the rate at which the photoperiod shortened, increasing linearly with increases in the rate of change in photoperiod between 0 and 3 min d−1. These results suggest shortening photoperiods control the first stage of the hardening process by regulating the rate of hardening. Frost hardening was inherently unstable once the maximum hardiness was reached since spontaneous dehardening occurred in spite of the controlled conditions. Dehardening also occurred when the photoperiod was lengthened suggesting that the cue for dehardening to commence was the shift from shortening to lengthening photoperiods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1989.tb01235.x
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  • 2
    Electronic Resource
    Electronic Resource
    Multivariate analysis of intraspecific responses to UV-B radiation in white clover (Trifolium repens L.) (2001)
    Oxford, UK : Blackwell Science Ltd.
    Plant, cell & environment 24 (2001), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: White clover (Trifolium repens L.) is experiencing increased levels of ultraviolet-B (UV-B) radiation in temperate pastures due to the depletion of the stratospheric ozone layer. Based on 17 morphological, morphogenetic and physiological attributes, this study analysed the consequences of enhanced UV-B on 26 white clover populations using principal components analysis (PCA). After 18 d of exposure to 13·3 kJ m−2 d−1 UV-B in controlled environments, UV-B significantly decreased above-ground and below-ground plant growth attributes, epidermal cell surface area and maximum quantum efficiency of photosystem II photochemistry (Fv/Fm). Aspects of cell division and cell expansion both were negatively affected by UV-B. Stomatal density, specific leaf mass, root-to-shoot ratio and levels of UV-B-absorbing compounds increased in response to UV-B. In the multivariate analysis, the main dimension of UV-B sensitivity was characterized by changes in plant growth attributes. Alterations in partitioning within and between plant organs constituted a secondary tier of UV-B responsiveness. Plant characteristics related to UV-B tolerance included lower growth rate, smaller epidermal cell surface area and higher UV-B-induced levels of UV-B-absorbing compounds. The results suggest overall UV-B tolerance for slower-growing populations from less productive habitats with higher natural UV-B irradiance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2001.00749.x
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  • 3
    Electronic Resource
    Electronic Resource
    Regulation of the loss of frost hardiness in Pinus radiata by photoperiod and temperature (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. In controlled environments, the interactive effects of warm (16: 8°C, day: night) and cool (12: 4°C, day: night) temperatures and long (13.5 h) and short (10 h) photoperiods on the dehardening of seedlings of Pinus radiata D. Don were investigated. In another experiment, the effect of four photoperiods from 9 to 14 h was examined. In a third, dehardening at constant temperatures from 5 to 17°C was followed. There was no evidence for an interaction between photoperiod and temperature. Dehardening was temporarily delayed by photoperiods below about 10 h, but there was no other quantitative effect of photoperiod. At constant temperatures, the rate of dehardening was initially constant but declined as the minimum summer frost hardiness was reached. In the initial phase the rate of dehardening was a linear function of temperature, increasing from 0.05°C day−1 at 8°C to 0.30 °C day−1 at 17°C. Temperature controlled the loss of frost hardiness by regulating the rate of dehardening.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1985.tb01217.x
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  • 4
    Electronic Resource
    Electronic Resource
    Photosynthesis and carbon export in white clover plants grown at various levels of phosphorus supply (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 73 (1988), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Net photosynthesis, concurrent carbon export and starch, sucrose and inorganic phosphorus concentrations were measured in leaves of white clover (Trifolium repens L. cv. Grasslands Huia) grown at four levels of phosphorus supply in the presence or absence of mineral nitrogen. The nitrogen treatments had no effect on growth, photosyntheis or carbon export. At the three higher levels of phosphorus supply, the amount of carbon exported was about 77% of net fixation. Photosynthesis and export per leaf decreased with phosphorus supply, primarily through the effect of phosphorus supply on leaf area. The rate of photosynthesis was reduced only at the lowest level of phosphorus supply.Inorganic phosphorus rose with phosphorus supply but starch concentration was unaffected. Sucrose was reduced at the lowest level of phosphorus supply but not significantly affected at higher levels. The ratio between starch and sucrose concentration was also unaffected at the higher levels, but was increased at the lowest level of supply. There thus appeared to be direct effects of phosphorus supply on photosynthesis, partitioning of carbon to carbohydrates and, by implication, export, only at the lowest level of phosphorus supply. As leaf area and plant growth were affected over the whole range of phosphorus supply, factors other than photosynthesis per se must have determined the response of growth to phosphorus supply.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1988.tb09191.x
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  • 5
    Electronic Resource
    Electronic Resource
    Photoinhibition and recovery of photosynthesis in intact barley leaves at 5 and 20°C (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 81 (1991), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Photoinhibition of photosynthesis and its recovery were studied in intact barley (Hordeum vuigare L. cv. Gunilla) leaves grown in a controlled environment by exposing them to two temperatures, 5 and 20°C, and a range of photon flux densities in excess of that during growth. Additionally, photoinhibtion was examined in the presence of chloramphenicol (CAP, an inhibitor of chloroplast protein synthesis) and of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). Susceptibility to photoinhibition was much higher at 5 than at 20°C. Furthermore, at 20°C. CAP exacerbated photoinhibition strongly, whereas CAP had little additional effect (10%) at 5°C. These results support the model that net photoinhibition is the difference between the inactivation and repair of photosystem II (PSII); i.e. the degradation and synthesis of the reaction centre protein, Dl. Furthermore, the steady-state extent of photoinhibition was strongly dependent on temperature and the results indicated this was manifested through the effects of temperature on the repair process of PSII. We propose that the continuous repair of PS II at 20°C conferred at least some protection from photoinhibition. At 5°C the repair process was largely inhibited, with increased photoinhibition as a consequence. However, we suggest where repair is inhibited by low temperature, some protection is alternatively conferred by the photoinhibited reaction centres. Providing they are not degraded, such centres could still dissipate excitation energy non-radiatively, thereby conferring protection of remaining photochemically active centres under steady-state conditions.A fraction of PS II centres were capable of resisting photoinhibition when the repair process was inhibited by CAP. This is discussed in relation to PS II heterogeneity. Furthermore, the repair process was not apparently activated within 3 h when barley leaves were transferred to photoinhibitory light conditions at 20°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1991.tb02130.x
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  • 6
    Electronic Resource
    Electronic Resource
    The relationship between stomatal conductance, transpiration rate and tracheid structure in Pinus radiata clones grown at different water vapour saturation deficits (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 6 (1983), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Stomatal conductance and needle water potential of P. radiata clones were measured after 2, 5 and 8 months on plants grown in controlled environment rooms with markedly different water vapour saturation deficits (D). Conductance was significantly lower at high D, but water potential differences between treatments were not significant. When trees were moved between treatments most of the changes in conductances occurred within 2 h, with residual changes after 24 h. Water potentials were not different 24 h after the trees were moved. The effects were completely reversible.Transpiration rates of individual trees were highest in the high D treatment and lowest in the low D treatment. They were not linearly related to D because of decreasing conductance with increasing D.Height growth, diameter growth and foliage areas were not significantly different between treatments. Tracheid lumen diameters tended to be larger in trees grown at higher D although treatment differences were not significant.There were significant clonal differences in shoot conductance and tracheid dimensions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11589331
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  • 7
    Electronic Resource
    Electronic Resource
    Photoinhibition of photosynthesis in intact kiwifruit (Actinidia deliciosa) leaves: effect of growth temperature on photoinhibition and recovery (1989)
    Springer
    Planta 180 (1989), S. 32-39 
    Details
    ISSN: 1432-2048
    Keywords: Actinidia ; Chlorophyll fluorescence ; Growth temperature ; Photoinhibition of photosynthesis (recovery) ; Temperature and photoinhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Intact leaves of kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson) from plants grown in a range of controlled temperatures from 15/10 to 30/25°C were exposed to a photon flux density (PFD) of 1500 μmol·m−2·s−1 at leaf temperatures between 10 and 25°C. Photoinhibition and recovery were followed at the same temperatures and at a PFD of 20 μmol·m−2·s−1, by measuring chlorophyll fluorescence at 77 K and 692 nm, by measuring the photon yield of photosynthetic O2 evolution and light-saturated net photosynthetic CO2 uptake. The growth of plants at low temperatures resulted in chronic photoinhibition as evident from reduced fluorescence and photon yields. However, low-temperature-grown plants apparently had a higher capacity to dissipate excess excitation energy than leaves from plants grown at high temperatures. Induced photoinhibition, from exposure to a PFD above that during growth, was less severe in low-temperature-grown plants, particularly at high exposure temperatures. Net changes in the instantaneous fluorescence,F 0, indicated that little or no photoinhibition occurred when low-temperature-grown plants were exposed to high-light at high temperatures. In contrast, high-temperature-grown plants were highly susceptible to photoinhibitory damage at all exposure temperatures. These data indicate acclimation in photosynthesis and changes in the capacity to dissipate excess excitation energy occurred in kiwifruit leaves with changes in growth temperature. Both processes contributed to changes in susceptibility to photoinhibition at the different growth temperatures. However, growth temperature also affected the capacity for recovery, with leaves from plants grown at low temperatures having moderate rates of recovery at low temperatures compared with leaves from plants grown at high temperatures which had negligible recovery. This also contributed to the reduced susceptibility to photoinhibition in low-temperature-grown plants. However, extreme photoinhibition resulted in severe reductions in the efficiency and capacity for photosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02411407
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  • 8
    Electronic Resource
    Electronic Resource
    Photoinhibition of photosynthesis in intact kiwifruit (Actinidia deliciosa) leaves: Changes in susceptibility to photoinhibition and recovery during the growth season (1992)
    Springer
    Planta 186 (1992), S. 418-425 
    Details
    ISSN: 1432-2048
    Keywords: Actinidia ; Chlorophyll fluorescence ; Growth season ; Photoinhibition of photosynthesis ; Photosynthesis (photoinhibition) ; Temperature and photoinhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson) plants grown in an outdoor enclosure were exposed to the natural conditions of temperature and photon flux density (PFD) over the growing season (October to May). Temperatures ranged from 14 to 21° C while the mean monthly maximum PFD varied from 1000 to 1700 μmol · m−2 · s−1, although the peak PFDs exceeded 2100 μmol · m−2 · s−1. At intervals, the daily variation in chlorophyll fluorescence at 692 nm and 77K and the photon yield of O2 evolution in attached leaves was monitored. Similarly, the susceptibility of intact leaves to a standard photoinhibitory treatment of 20° C and a PFD of 2000 μmol · m−2 · s−1 and the ability to recover at 25° C and 20 μmol · m−2 · s−2 was followed through the season. On a few occasions, plants were transferred either to or from a shade enclosure to assess the suceptibility to natural photoinhibition and the capacity for recovery. There were minor though significant changes in early-morning fluorescence emission and photon yield throughout the growing season. The initial fluorescence, Fo, and the maximum fluorescence, Fm, were, however, significantly and persistently different from that in shade-grown kiwifruit leaves, indicative of chronic photoinhibition occurring in the sun leaves. In spring and autumn, kiwifruit leaves were photoinhibited through the day whereas in summer, when the PFDs were highest, no photoinhibition occurred. However, there was apparently no non-radiative energy dissipation occurring then also, indicating that the kiwifruit leaves appeared to fully utilize the available excitation energy. Nevertheless, the propensity for kiwifruit leaves to be susceptible to photoinhibition remained high throughout the season. The cause of a discrepancy between the severe photoinhibition under controlled conditions and the lack of photoinhibition under comparable, natural conditions remains uncertain. Recovery from photoinhibition, by contrast, varied over the season and was maximal in summer and declined markedly in autumn. Transfer of shade-grown plants to full sun had a catastrophic effect on the fluorescence characteristics of the leaf and photon yield. Within 3 d the variable fluorescence, Fv, and the photon yield were reduced by 80 and 40%, respectively, and this effect persisted for at least 20 d. The restoration of fluorescence characteristics on transfer of sun leaves to shade, however, was very slow and not complete within 15 d.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195323
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  • 9
    Electronic Resource
    Electronic Resource
    Photoinhibition of photosynthesis in intact bean leaves: role of light and temperature, and requirement for chloroplast-protein synthesis during recovery (1986)
    Springer
    Planta 168 (1986), S. 253-260 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll fluorescence ; Light and photoinhibition ; Phaseolus (photoinhibition) ; Photoinhibition of photosynthesis (recovery) ; Temperature and photoinhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photoinhibition of photosynthesis was induced in intact leaves of Phaseolus vulgaris L. grown at a photon flux density (PFD; photon fluence rate) of 300 μmol·m-2·s-1, by exposure to a PFD of 1400 μmol·m-2·s-1. Subsequent recovery from photoinhibition was followed at temperatures ranging from 5 to 35°C and at a PFD of either 20 or 140 μmol·m-2·s-1 or in complete darkness. Photoinhibition and recovery were monitored mainly by chlorophyll fluorescence emission at 77K but also by photosynthetic O2 evolution. The effects of the protein-synthesis inhibitors, cycloheximide and chloramphenicol, on photoinhibition and recovery were also determined. The results demonstrate that recovery was temperature-dependent with rates slow below 15°C and optimal at 30°C. Light was required for maximum recovery but the process was light-saturated at a PFD of 20 μmol·m-2·s-1. Chloramphenicol, but not cycloheximide, inactivated the repair process, indicating that recovery involved the synthesis of one or more chloroplast-encoded proteins. With chloramphenicol, it was shown that photoinhibition and recovery occurred concomitantly. The temperature-dependency of the photoinhibition process was, therefore, in part determined by the effect of temperature on the recovery process. Consequently, photoinhibition is the net difference between the rate of damage and the rate of repair. The susceptibility of chilling-sensitive plant species to photoinhibition at low temperatures is proposed to result from the low rates of recovery in this temperature range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00402971
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  • 10
    Electronic Resource
    Electronic Resource
    Photoinhibition of photosynthesis in intact kiwifruit (Actinidia deliciosa) leaves: Effect of temperature (1988)
    Springer
    Planta 174 (1988), S. 152-158 
    Details
    ISSN: 1432-2048
    Keywords: Actinidia ; Chlorophyll fluorescence ; Light and photoinhibition ; Photoinhibition of photosynthesis ; Temperature and photoinhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photoinhibition of photosynthesis was induced in attached leaves of kiwifruit grown in natural light not exceeding a photon flux density (PFD) of 300 μmol·m-2·s-1, by exposing them to a PFD of 1500 μmol·m-2·s-1. The temperature was held constant, between 5 and 35° C, during the exposure to high light. The kinetics of photoinhibition were measured by chlorophyll fluorescence at 77K and the photon yield of photosynthetic O2 evolution. Photoinhibition occurred at all temperatures but was greatest at low temperatures. Photoinhibition followed pseudo first-order kinetics, as determined by the variable fluorescence (F v) and photon yield, with the long-term steady-state of photoinhibition strongly dependent on temperature wheareas the observed rate constant was only weakly temperature-dependent. Temperature had little effect on the decrease in the maximum fluorescence (F m) but the increase in the instantaneous fluorescence (F o) was significantly affected by low temperatures in particular. These changes in fluorescence indicate that kiwifruit leaves have some capacity to dissipate excessive excitation energy by increasing the rate constant for non-radiative (thermal) energy dissipation although temperature apparently had little effect on this. Direct photoinhibitory damage to the photosystem II reaction centres was evident by the increases in F o and extreme, irreversible damage occurred at the lower temperatures. This indicates that kiwifruit leaves were most susceptible to photoinhibition at low temperatures because direct damage to the reaction centres was greatest at these temperatures. The results also imply that mechanisms to dissipate excess energy were inadequate to afford any protection from photoinhibition over a wide temperature range in these shade-grown leaves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394766
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