Bodner M, Beck E
Institut für Botanik der Universität Innsbruck, Sternwartestrasse 15, A-6020, Innsbruck, Austria.
Lehrstuhl für Pflanzenphysiologie der Universität Bayreuth, Universitätsstrasse 30, D-8580, Bayreuth, Federal Republic of Germany.
Oecologia. 1987 Jun;72(3):366-371. doi: 10.1007/BF00377565.
The effect of supercooling and freezing on the photosynthetic capability of representatives of the permanent frost hardy giant rosette plants Dendrosenecio keniodendron, D. brassica and Lobelia telekii, of the tropical alpine regions was investigated with the non-invasive chlorophyll a fluorescence technique. While supercooling, normal chlorophyll a fluorescence kinetics exhibiting the sequence 0, I, (D), P, S, M, were recorded, however with some retardation of both, the fast and the slow characteristics as compared to those obtained at day-time temperature. As long as the leaves remained unfrozen, the rise of the variable fluorescence F from the level 0 to P was inversely related to a drop of the temperature from about 0°C to-8°C. The increase of F with lower temperature is understood to result from a decrease of the velocity of the quenching reactions while photoreduction of the primary electron acceptor appeared to be unimpeded. The second fluorescence maximum (M), usually interpreted to indicate the commencement of the biochemical reactions of photosynthesis was consistenly to be observed during supercooling. Fluoescence induction kinetics of frozen leaves showed only fast rise to presumably F which was not followed by a significant decay for as long as 4 min. The lack of substantial quenching indicates that in the freeze-dehydrated state neither reoxidation of the primary acceptor nor energetization of the thylakoid membrane was accomplished. This effect however was immediately and fully reserved upon thawing of the leaves when the usual fluorescence induction kinetics as well as normal rates of CO-uptake were observed. Thus the permanent frost-hardy afroalpine plants do not exhibit any even short-term memory effect of the nocturnal frost on such a delicate process as is photosynthesis.
采用非侵入性叶绿素a荧光技术，研究了过冷和冷冻对热带高山地区永久性耐寒巨型莲座植物齿叶千里光、甘蓝叶千里光和高山半边莲光合能力的影响。过冷时，记录到正常的叶绿素a荧光动力学，呈现出0、I、（D）、P、S、M的顺序，但与白天温度下相比，快速和慢速特征均有一定延迟。只要叶片未结冰，可变荧光F从0水平上升到P与温度从约0°C下降到 -8°C呈负相关。较低温度下F的增加被认为是猝灭反应速度降低的结果，而初级电子受体的光还原似乎未受阻碍。在过冷过程中，通常被解释为光合作用生化反应开始的第二个荧光最大值（M）始终可以观察到。冷冻叶片的荧光诱导动力学仅显示快速上升到可能的F，并且在长达4分钟内没有明显衰减。缺乏显著的猝灭表明，在冷冻脱水状态下，初级受体的再氧化和类囊体膜的能量化均未完成。然而，当观察到正常的荧光诱导动力学以及正常的CO吸收速率时，叶片解冻后这种效应立即完全恢复。因此，永久性耐寒的非洲高山植物在光合作用这样的微妙过程中，不会表现出任何即使是短期的夜间霜冻记忆效应。
