Yahyaoui W, Harnois J, Carpentier R
Groupe de Recherche en Energie et Information Biomoléculaires, Université du Québec à Trois-Rivières, Canada.
FEBS Lett. 1998 Nov 27;440(1-2):59-63. doi: 10.1016/s0014-5793(98)01430-6.
When plant leaves or chloroplasts are exposed to illumination that exceeds their photosynthetic capacity, photoprotective mechanisms such as described by the energy-dependent (non-photochemical) quenching of chlorophyll fluorescence are involved. The protective action is attributed to an increased rate constant for thermal dissipation of absorbed quanta. We applied photoacoustic spectroscopy to monitor thermal dissipation in spinach thylakoid membranes together with simultaneous measurement of chlorophyll fluorescence in the presence of inhibitors of opposite action on the formation of delta pH across the thylakoid membrane (tentoxin and nigericin/valinomycin). A linear relationship between the appearance of fluorescence quenching during formation of the delta pH and the reciprocal variation of thermal dissipation was demonstrated. Dicyclohexylcarbodiimide, which is known to prevent protonation of the minor light-harvesting complexes of photosystem II, significantly reduced the formation of fluorescence quenching and the concurrent increase in thermal dissipation. However, the addition of exogenous ascorbate to activate the xanthophyll de-epoxidase increased non-photochemical fluorescence quenching without affecting the measured thermal dissipation. It is concluded that a portion of energy-dependent fluorescence quenching that is independent of de-epoxidase activity can be readily measured by photoacoustic spectroscopy as an increase in thermal deactivation processes.
当植物叶片或叶绿体暴露于超过其光合能力的光照下时，就会涉及到诸如叶绿素荧光的能量依赖性（非光化学）猝灭等光保护机制。这种保护作用归因于吸收量子的热耗散速率常数增加。我们应用光声光谱法监测菠菜类囊体膜中的热耗散，并同时测量在存在对类囊体膜两侧ΔpH形成具有相反作用的抑制剂（毒莠定和尼日利亚菌素/缬氨霉素）时的叶绿素荧光。结果表明，在ΔpH形成过程中荧光猝灭的出现与热耗散的倒数变化之间存在线性关系。已知二环己基碳二亚胺可阻止光系统II的次要捕光复合物质子化，它显著降低了荧光猝灭的形成以及同时发生的热耗散增加。然而，添加外源抗坏血酸以激活叶黄素脱环氧化酶增加了非光化学荧光猝灭，而不影响所测量的热耗散。得出的结论是，一部分与脱环氧化酶活性无关的能量依赖性荧光猝灭可以通过光声光谱法很容易地测量为热失活过程的增加。
