Institute for Biochemistry of Plants, University of Düsseldorf, Universitätsstrasse 1, D-4000, Düsseldorf 1, Federal Republic of Germany.
Planta. 1989 Mar;177(3):409-16. doi: 10.1007/BF00403600.
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.
在 20°C 和 77K 下通过荧光诱导测量，并通过测定 O2 演化的量子产率，研究了低温下中等光照对未硬化（适应于+18°C）和硬化（冷驯化）菠菜（Spinacea oleracea L.）叶片光合作用的影响。在+4°C 下暴露于 550 μmol 光子·m(-2)·s(-1) 会在几小时内导致未硬化叶片强烈的光抑制。通过初始荧光（F o）的增加和可变荧光（F v）和可变荧光与最大荧光（F V/F M）比值的降低来表征光抑制，在 77K 和 20°C 下均表现出光抑制。量子产率的下降与在 20°C 下测量的 F V/F M 比值的下降更为密切相关，而与在 77K 下的 F V/F M 比值相比。光系统 II 的可变荧光猝灭伴随着在 77K 时光系统 I 荧光的下降，表明作为光处理主要后果的色素热去激发增加。在低光照下，在较高温度下 1-3 小时内，所有这些在荧光参数以及 O2 演化的量子产率中检测到的变化都完全可逆。快速恢复使我们认为这种光抑制代表了一种调节机制，通过增加热能耗散来保护光合作用装置免受过量光的不利影响。长期的冷驯化可能会加强其他保护机制，因为硬化叶片对相同的光处理不敏感，而相同的光处理会导致未硬化叶片光合作用强烈抑制。
