Loss of functional Photosystem II reaction centres in zooxanthellae of corals exposed to bleaching conditions:: using fluorescence rise kinetics
Loss of functional Photosystem II reaction centres in zooxanthellae of corals exposed to bleaching conditions:: using fluorescence rise kinetics
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DOI：
10.1023/b:pres.0000040444.41179.09
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发表时间：
2004-01-01
影响因子：
3.7
通讯作者：
Ralph, PJ
中科院分区：
文献类型：
--
作者：
Hill, R;Larkum, AWD;Ralph, PJ
大量的珊瑚白化与海水表面温度升高有关，在强光期间，海水表面温度比平均温度高1 - 2度。这些条件诱导虫黄藻从珊瑚宿主排出，以响应藻类共生体的光合作用损害。触发这种释放的机制尚未明确确定，为了进一步了解这一过程，首次研究了荧光上升动力学。暴露于高温（33℃）和光照(280 μ mol光子m（-2) s(-1)）下的珊瑚在叶绿素-a荧光的快速多相诱导方面表现出明显的变化，表明光化学过程中的生物物理变化。用PEA荧光计和成像- pam对三种珊瑚的前2000毫秒荧光上升进行了长达8小时的监测。damicornis对光合器官的影响最小，而Acropora nobilis对光合器官最敏感，而cyhastrea serailia则介于其他两种之间。紫菀在漂白条件下表现出显著的恢复能力。三种植物的初始上升斜率和j瞬态高度均呈下降趋势，表明在高温条件下，光合系统II （PS II）中心功能丧失。当暴露于漂白胁迫时，光化学猝灭的下降证实了PS II中心的显著损失。非光化学猝灭被认为是在漂白条件下以热形式耗散多余能量的重要机制。光磷酸化可以解释PS II活性的下降。状态转变是非光化学猝灭的一个组成部分，可能是漂白过程中高度非光化学猝灭的原因，这一机制与磷酸化诱导的光收集配合物与PS II反应中心的解离有关。这一可逆过程可能解释了珊瑚的恢复，特别是在黄花珊瑚中。
Mass coral bleaching is linked to elevated sea surface temperatures, 1 - 2 degreesC above average, during periods of intense light. These conditions induce the expulsion of zooxanthellae from the coral host in response to photosynthetic damage in the algal symbionts. The mechanism that triggers this release has not been clearly established and to further our knowledge of this process, fluorescence rise kinetics have been studied for the first time. Corals that were exposed to elevated temperature (33 degreesC) and light (280 mumol photons m(-2) s(-1)), showed distinct changes in the fast polyphasic induction of chlorophyll-a fluorescence, indicating biophysical changes in the photochemical processes. The fluorescence rise over the first 2000 ms was monitored in three species of corals for up to 8 h, with a PEA fluorometer and an imaging-PAM. Pocillopora damicornis showed the least impact on photosynthetic apparatus, while Acropora nobilis was the most sensitive, with Cyphastrea serailia intermediate between the other two species. A. nobilis showed a remarkable capacity for recovery from bleaching conditions. For all three species, a steady decline in the slope of the initial rise and the height of the J-transient was observed, indicating the loss of functional Photosystem II ( PS II) centres under elevated-temperature conditions. A significant loss of PS II centres was confirmed by a decline in photochemical quenching when exposed to bleaching stress. Non-photochemical quenching was identified as a significant mechanism for dissipating excess energy as heat under the bleaching conditions. Photophosphorylation could explain this decline in PS II activity. State transitions, a component of non-photochemical quenching, was a probable cause of the high non-photochemical quenching during bleaching and this mechanism is associated with the phosphorylation-induced dissociation of the light harvesting complexes from the PS II reaction centres. This reversible process may account for the coral recovery, particularly in A. nobilis.