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  • 1
    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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  • 2
    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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  • 3
    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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  • 4
    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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  • 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
    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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  • 7
    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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  • 8
    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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  • 9
    Electronic Resource
    Electronic Resource
    Photoinhibition of photosynthesis in intact kiwifruit (Actinidia deliciosa) leaves: Recovery and its dependence on temperature (1988)
    Springer
    Planta 174 (1988), S. 159-165 
    Details
    ISSN: 1432-2048
    Keywords: Actinidia ; Chlorophyll fluorescence ; Photoinhibition of photosynthesis ; Temperature and recovery from photoinhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Recovery of photoinhibition in intact leaves of shade-grown kiwifruit was followed at temperatures between 10° and 35° C. Photoinhibition was initially induced by exposing the leaves for 240 min to a photon flux density (PFD) of 1 500 μmol·m-2·s-1 at 20° C. In additional experiments to determine the effect of extent of photoinhibition on recovery, this period of exposure was varied between 90 and 400 min. The kinetics of recovery were followed by chlorophyll fluorescence at 77K. Recovery was rapid at temperatures of 25–35° and slow or negligible below 20° C. The results reinforce those from earlier studies that indicate chilling-sensitive species are particularly susceptible to photoinhibition at low temperatures because of the low rates of recovery. At all temperatures above 15° C, recovery followed pseudo first-order kinetics. The extent of photoinhibition affected the rate constant for recovery which declined in a linear fashion at all temperatures with increased photoinhibition. However, the extent of photoinhibition had little effect on the temperature-dependency of recovery. An analysis of the fluorescence characteristics indicated that a reduction in non-radiative energy dissipation and repair of damaged reaction centres contributed about equally to the apparent recovery though biochemical studies are needed to confirm this. From an interpretation of the kinetics of photoinhibition, we suggest that recovery occurring during photoinhibition is limited by factors different from those that affect post-photoinhibition recovery.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394767
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  • 10
    Electronic Resource
    Electronic Resource
    Photoinhibition of photosynthesis in intact kiwifruit (Actinidia deliciosa) leaves: Effect of light during growth on photoinhibition and recovery (1988)
    Springer
    Planta 175 (1988), S. 355-363 
    Details
    ISSN: 1432-2048
    Keywords: Actinidia ; Chlorophyll fluorescence ; Light and growth ; Light and photoinhibition ; Photoinhibition of photosynthesis (recovery) ; Photosynthesis (photon yield) ; Temperature and photoinhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photoinhibition of photosynthesis was induced in intact kiwifruit (Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson) leaves grown at two photon flux densities (PFDs) of 700 and 1300 μmol·m-2·s-1 in a controlled environment, by exposing the leaves to PFD between 1000 and 2000 μmol·m-2·s-1 at temperatures between 10 and 25°C; recovery from photoinhibition was followed at the same range of temperatures and at a PFD between 0 and 500 μmol·m-2·s-1. In either case the time-courses of photoinhibition and recovery were followed by measuring chlorophyll fluorescence at 692 nm and 77K and by measuring the photon yield of photosynthetic O2 evolution. The initial rate of photoinhibition was lower in the high-light-grown plants but the long-term extent of photoinhibition was not different from that in low-light-grown plants. The rate constants for recovery after photoinhibition for the plants grown at 700 and 1300 μmol·m-2·s-1 or for those grown in shade were similar, indicating that differences between sun and shade leaves in their susceptibility to photoinhibition could not be accounted for by differences in capacity for recovery during photoinhibition. Recovery following photoinhibition was increasingly suppressed by an increasing PFD above 20 μmol·m-2·s-1, indicating that recovery in photoinhibitory conditions would, in any case, be very slow. Differences in photosynthetic capacity and in the capacity for dissipation of non-radiative energy seemed more likely to contribute to differences in susceptibility to photoinhibition between sun and shade leaves of kiwifruit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00396341
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