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  • 1
    Electronic Resource
    Electronic Resource
    Inhibition of photosynthetic reactions by light (1985)
    Springer
    Planta 163 (1985), S. 218-226 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll fluorescence ; Chloroplast, isolated ; Photoinhibition ; Photosynthesis (electron transport) ; Spinacia (photoinhibition)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Illumination of isolated intact chloroplasts of Spinacia oleracea L. for 10 min with 850 W m-2 red light in the absence of substrate levels of bicarbonate caused severe inhibition of subsequently measured photosynthetic activities. The capacity of CO2-dependent O2 evolution and of non-cyclic electron transport were impaired to similar degrees. This photoinactivation was prevented by addition of bicarbonate which allowed normal carbon metabolism to proceed during preillumination. Photoinhibition of electron transport was observed likewise upon illumination of intact or broken chloroplasts when efficient electron acceptors were absent. Addition of uncouplers did not influence the extent of inhibition. Studies of partial electron-transport reactions indicated that the activity of both photosystems was affected by light. In addition, the water-oxidation system or its connection to photosystem II seemed to be impaired. Preillumination did not cause uncoupling of photophosphorylation. Chlorophyll-fluorescence data obtained at room temperature and at 77 K are consistent with the view that photosystem-II reaction centers were altered. Addition of superoxide dismutase (EC 1.15.1.1), catalase (EC 1.11.1.6) or 1,4-diazabicyclo(2,2,2)octane to isolated thylakoids prior to preillumination substantially diminished photoinhibition. This result shows that reactive oxygen species were involved in the damage. It is concluded that bright light, which normally does not damage the photosynthetic apparatus, may exert the described destructive effects under conditions that restrict metabolic turnover of photosynthetic energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393510
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  • 2
    Electronic Resource
    Electronic Resource
    O2-dependent inhibition of photosynthetic capacity in intact isolated chloroplasts and isolated cells from spinach leaves illuminated in the absence of CO2 (1978)
    Springer
    Planta 142 (1978), S. 229-233 
    Details
    ISSN: 1432-2048
    Keywords: Chloroplasts ; Leaf cells ; Photoinhibition ; Photorespiration ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When isolated intact chloroplasts or cells from spinach (Spinacia oleracea L.) leaves are incubated in the light in the absence of CO2, their capacity for subsequent CO2-dependent photosynthetic oxygen evolution is drastically decreased. This inhibition is light and oxygen-dependent and can be prevented by addition of bicarbonate. It is concluded that the normal dissipation of photosynthetic energy by carbon assimilation and in processes related to photorespiration is an essential condition for the physiological stability of illuminated intact chloroplasts and cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00388218
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Photoinhibition at chilling temperature (1989)
    Springer
    Planta 177 (1989), S. 409-416 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll fluorescence ; Cold acclimation ; Photoinhibition ; Photosynthesis (inhibition) ; Quantum yield ; Spinacia (cold acclimation)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of moderate light at chilling temperature on the photosynthesis of unhardened (acclimated to +18° C) and hardened (cold-acclimated) spinach (Spinacea oleracea L.) leaves were studied by means of fluorescence-induction measurements at 20° C and 77K and by determination of quantum yield of O2 evolution. Exposure to 550 μmol photons·m-2·s-1 at +4° C induced a strong photoinhibition in the unhardened leaves within a few hours. Photoinhibition manifested by a decline in quantum yield was characterized by an increase in initial fluorescence (F o) and a decrease in variable fluorescence (F v) and in the ratio of variable to maximum fluorescence (F V/F M), both at 77K and 20° C. The decline in quantum yield was more closely related to the decrease in the F V/F M ratio measured at 20° C, as compared with F V/F M at 77K. Quenching of the variable fluorescence of photosystem II was accompanied by a decline in photosystem-I fluorescence at 77K, indicating increased thermal de-excitation of pigments as the main consequence of the light treatment. All these changes detected in fluorescence parameters as well as in the quantum yield of O2 evolution were fully reversible within 1–3 h at a higher temperature in low light. The fast recovery led us to the view that this photoinhibition represents a regulatory mechanism protecting the photosynthetic apparatus from the adverse effects of excess light by increasing thermal energy dissipation. Long-term cold acclimation probably enforces other protective mechanisms, as the hardened leaves were insensitive to the same light treatment that induced strong inhibition of photosynthesis in unhardened leaves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00403600
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Photoinhibition of photosynthesis under anaerobic conditions studied with leaves and chloroplasts of Spinacia oleracea L. (1985)
    Springer
    Planta 165 (1985), S. 430-438 
    Details
    ISSN: 1432-2048
    Keywords: Anaerobiosis ; Chlorophyll a fluorescence ; Photoinhibition ; Photosynthesis (CO2 assimilation, electron transport) ; Spinacia (photoinhibition) ; Thylakoids, isolated
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The role of oxygen in the photoinactivation of the photosynthetic apparatus of Spinacia oleracea L. was investigated. Moderate irradiation (1200 μmol photons m-2s-1) of spinach leaves in an atmosphere of pure nitrogen caused strong inhibition of subsequently measured net CO2 assimilation, whereas considerably less photoinhibition was observed in the presence of low partial pressures (10–20 mbar) of O2. The decrease in activity caused by anaerobiosis in the light was not based on stomatal closure; the decline of assimilation represents a photoinhibition, as activity was not impaired by low irradiation (80 μmol photos m-2s-1). In contrast, gassing with pure N2 in the dark caused strong inhibition. Electron-transport rates and chlorophyll-fluorescence data of thylakoids isolated from photoinhibited leaves indicated damage to the electron-transport system, in particular to photosystem II reaction centers. In vitro, photoinhibition in isolated thylakoid membranes was also strongly promoted by anaerobiosis. Photoinhibition of electron-transport rates under anaerobic conditions was characterized by a pronounced increase in the initial fluorescence level, F0, of chlorophyll-fluorescence induction, in contrast to photoinhibition under aerobic conditions. The results are discussed in terms of two mechanisms of photoinhibition, one that is suppressed and a second that is promoted by oxygen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392242
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    Paper (German National Licenses)
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