Dept of Biology, Univ of Turku, SF-20500 Turku, Finland Institute for Biochemistry of Plants, Heinrich Heine Univ., Universittsstrasse 1, D-4000 Düsseldorf FRG.
Physiol Plant. 1990 Aug;79(4):617-22. doi: 10.1111/j.1399-3054.1990.tb00034.x.
The role of high light stress in a natural environment was studied on spinach plants (Spinacia oleracea L. cv. Wolter) grown in the field during the winter season. Fluorescence induction (at 293 K and 77 K) of leaves was used to characterize the stress effects. Night frost with minimum temperatures between - 1.5°C and -7.5°C (i.e. above the'frost killing point'at ca. -11.5°C) led to impaired photosynthesis. This was seen as increased initial fluorescence (F(o) ), decreased ratio of variable to maximum fluorescence (F(V) /F(M) ) and lowered rates of O(2) evolution. The freezing injury was reversible within several frostless days. Exposure to high light (about 900 mol m(-2) s(-1) ) at chilling temperatures in the field caused photoinhibition, manifested as decreased variable fluorescence (F(V) ) and F(V) /F(M) ratio without changes in F(O) . The photoinhibitory fluorescence quenching was not stronger after frost than after frostless nights; synergism between light stress and preceding freezing stress was not observed. Fluorescence induction signals at 77 K showed that F(V) of photosystems I and II decreased to the same extent, indicating increased thermal deactivation of excited chlorophyll. Photoinhibition was fully reversible at +4°C within 1 h in low light, but only partially in moderate light. Preceding night frosts did not affect the recovery. The photoinhibition observed here is regarded as a protective system of thermal dissipation of excess light energy.
冬季大田条件下，研究了高光胁迫在自然环境中的作用对菠菜（Spinacia oleracea L. cv. Wolter）的影响。采用叶片荧光诱导（293 K 和 77 K）来描述胁迫效应。夜间结霜，最低温度在-1.5°C 到-7.5°C 之间（即在约-11.5°C 的“霜害点”以上），导致光合作用受损。表现为初始荧光（F(o) ）增加、可变荧光与最大荧光的比值（F(V) / F(M) ）降低、O(2) 释放速率降低。在无霜数天内，冻结损伤是可逆的。在田间寒冷温度下，高光（约 900 μmol m(-2) s(-1) ）照射会引起光抑制，表现为可变荧光（F(V) ）和 F(V) / F(M) 比值降低，而 F(O) 不变。冻结后光抑制荧光猝灭并不比无冻结夜间更强；光胁迫和先前冻结胁迫之间没有观察到协同作用。77 K 下的荧光诱导信号表明，光系统 I 和 II 的 F(V) 均降低到相同程度，表明激发态叶绿素的热失活增加。在弱光下，4°C 下 1 小时内完全恢复，而在中等光照下仅部分恢复。先前的夜间结霜不会影响恢复。这里观察到的光抑制被认为是一种过量光能的热耗散保护系统。
