EFFECTS OF GROWTH IRRADIANCE AND NITROGEN LIMITATION ON PHOTOSYNTHETIC ENERGY-CONVERSION IN PHOTOSYSTEM-II
EFFECTS OF GROWTH IRRADIANCE AND NITROGEN LIMITATION ON PHOTOSYNTHETIC ENERGY-CONVERSION IN PHOTOSYSTEM-II
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DOI：
10.1104/pp.88.3.923
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发表时间：
1988-11-01
期刊：
影响因子：
7.4
通讯作者：
FALKOWSKI, P
中科院分区：
文献类型：
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作者：
KOLBER, Z;ZEHR, J;FALKOWSKI, P
研究了5种海洋单细胞藻（杜氏杜氏藻、海链藻、三链藻、三链藻和三链藻）的光合能量转化。weisfloptera，中肋骨条藻，球等鞭金藻），代表三个系统发育类，这是在稳态条件下生长的光或无机氮作为限制因素。使用泵浦和探针荧光技术，我们测量了可变荧光产率的最大变化，荧光产率变化的闪光强度饱和曲线和荧光产率衰减的动力学。在所有生长辐照水平下，营养充足的细胞表现出大致相同的荧光产率变化和相似的荧光衰减动力学。光系统II的表观相对吸收截面，从闪光强度饱和曲线的斜率计算，一般增加细胞阴影适应。在饱和泵浦闪光之后的荧光产率的衰减动力学可以表示为三个指数分量的总和，其中半衰期为160和600微秒以及30至300毫秒。各组分的相对贡献率随生长光强的变化不显著。然而，随着细胞变得更加氮限制，荧光产率的最大变化降低，并且伴随着160微秒荧光衰减分量的比例降低，这对应于电子从QA-转移到QB。荧光产率的变化也伴随着D1的水平的变化，这是一个蛋白质的反应中心II的组成部分，和CP 47，叶绿素蛋白形成的核心光系统II的一部分。这些结果与功能性光系统II反应中心的损失是一致的。此外，尽管总细胞叶绿素的损失，这总是伴随着氮限制，光系统II的表观吸收截面增加。我们的研究结果表明，氮限制导致光合能量转换效率大幅下降。
Photosynthetic energy conversion was investigated in five species of marine unicellular algae, (Dunaliella tertiolecta, Thalassiosira pseudonana, T. weisflogii, Skeletonema costatum, Isochrysis galbana) representing three phylogenetic classes, which were grown under steady state conditions with either light or inorganic nitrogen as a limiting factor. Using a pump and probe fluorescence technique we measured the maximum change in variable fluorescence yields, the flash intensity saturation curves for the change in fluorescence yields and the kinetics of the decay in fluorescence yields. Under all growth irradiance levels nutrient replete cells exhibited approximately the same changes in fluorescence yields and similar fluorescence decay kinetics. The apparent relative absorption cross-section of photosystem II, calculated from the slope of the flash intensity saturation curves, generally increased as cells shade adapted. The decay kinetics of the fluorescence yield following a saturating pump flash can be expressed as the sum of three exponential components, with half-times of 160 and 600 microseconds and 30 to 300 milliseconds. The relative contribution of each component did not change significantly with growth irradiance. As cells became more nitrogen limited, however, the maximum change in fluorescence yield decreased, and was accompanied by a decrease in the proportion of a 160 microsecond fluorescence decay component, which corresponds to the transfer of electrons from QA- to QB. Changes in fluorescence yields were also accompanied by changes in the levels of D1, a protein which is integral in reaction center II, and CP47, a chlorophyll protein forming part of the core of photosystem II. These results are consistent with a loss of functional photosystem II reaction centers. Moreover, in spite of losses of total cellular chlorophyll, which invariably accompanied nitrogen limitation, the apparent absorption cross-sections of photosystem II increased. Our results suggest that nitrogen limitation leads to substantial decreases in photosynthetic energy conversion efficiency.