Temperature-induced bleaching of corals begins with impairment of the CO2 fixation mechanism in zooxanthellae
Temperature-induced bleaching of corals begins with impairment of the CO2 fixation mechanism in zooxanthellae
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DOI：
10.1046/j.1365-3040.1998.00345.x
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发表时间：
1998-12-01
影响因子：
7.3
通讯作者：
Schreiber, U
中科院分区：
文献类型：
--
作者：
Jones, RJ;Hoegh-Guldberg, O;Schreiber, U
利用脉冲幅度调制（PAM）叶绿素荧光和光呼吸测定法研究了热应激对共生甲藻（zooxanthropium）在造礁珊瑚组织内光合作用的早期影响。在33 ℃和34 ℃下处理4 h，柱花草叶绿素荧光信号发生强烈的非光化学猝灭（qN），光合放氧显著降低，光系统II（PSII）的最佳量子产率（F-v/F-m）降低。量子产率下降到更大的程度上对珊瑚分支的照明表面比低（阴影）表面，也当高辐照强度与高温相结合（33摄氏度，而不是28摄氏度），当在不存在氧气的情况下进行淬火分析时，qN在热应力样品中塌陷。这些观察结果被解释为过量吸收能量的光保护耗散的开始，因为热（qN）和O-2依赖的电子流通过Mehler-抗坏血酸盐，过氧化物酶循环（MAP-循环）：光驱动电子传递速率超过卡尔文循环能力的点。提出了一个珊瑚漂白模型，即S. pistillata热损伤的主要部位是在卡尔文循环中的羧化，在高等植物热损伤期间已经观察到，PSII的损伤和F-v/F-m的降低（即光抑制）是光保护机制被光压倒之后的次要效应。这个次要因素增加了主要变量温度的影响。讨论了热胁迫下虫黄藻电子流的潜在限制与卡尔文循环酶和甲藻Rubisco的异常状态的关系。我们的模型的显著特点是：（1）PSII的损伤不是虫黄藻热胁迫序列的第一步，酸（2）光在漂白现象的起始中起着关键的次要作用。
The early effects of heat stress on the photosynthesis of symbiotic dinoflagellates (zooxanthellae) within the tissues of a reef-building coral were examined using pulse-amplitude-modulated (PAM) chlorophyll fluorescence and photorespirometry. Exposure of Stylophora pistillata to 33 and 34 degrees C for 4 h resulted in (1) the development of strong non-photochemical quenching (qN) of the chlorophyll fluorescence signal, (2) marked decreases in photosynthetic oxygen evolution, and (3) decreases in optimal quantum yield (F-v/F-m) of photosystern II (PSII), Quantum yield decreased to a greater extent on the illuminated surfaces of coral branches than on lower (shaded) surfaces, and also when high irradiance intensities were combined with elevated temperature (33 degrees C as opposed to 28 degrees C), qN collapsed in heat-stressed samples when quenching analysis was conducted in the absence of oxygen, Collectively, these observations are interpreted as the initiation of photoprotective dissipation of excess absorbed energy as heat (qN) and O-2-dependent electron flow through the Mehler-Ascorbate-Peroxidase cycle (MAP-cycle) following the point at which the rate of light-driven electron transport exceeds the capacity of the Calvin cycle. A model for coral bleaching is proposed whereby the primary site of heat damage in S, pistillata is carboxylation within the Calvin cycle, as has been observed during heat damage in higher plants, Damage to PSII and a reduction in F-v/F-m (i.e. photoinhibition) are secondary effects following the overwhelming of photoprotective mechanisms by light. This secondary factor increases the effect of the primary variable, temperature. Potential restrictions of electron flow in heat-stressed zooxanthellae are discussed with respect to Calvin cycle enzymes and the unusual status of the dinoflagellate Rubisco, Significant features of our model are that (1) damage to PSII is not the initial step in the sequence of heat stress in zooxanthellae, acid (2) light plays a key secondary role in the initiation of the bleaching phenomena.