Fluctuations in photosynthetic characteristics related to chloroplast translocation have been known in the foliose green algae Ulva lactuca var. latissima and var. rigida and U. mutabilis according to photoperiod. In Ulva, the single parietal chloroplast is found along the thallus surface wall and exhibits high photosynthetic activity during the light period; the chloroplast then moves towards the side walls and shows low photosynthetic activity during the dark period. In this study, we re‐investigated whether the photosynthetic ability is dependent on chloroplast location in a unialgal culture of U. conglobata grown and maintained under low irradiance regime by analyzing in vivo absorption spectra, oxygen evolution, and pulse amplitude modulation chlorophyll fluorescence. The light absorbance of the thallus was higher when chloroplast was along the thallus surface wall than when along the side walls and, therefore, the thallus absorbance at 680 nm was used as an index of chloroplast position. Some photosynthetic parameters such as maximum net photosynthetic rate per thallus area and effective quantum yield of photosystem II correlated with the thallus absorbance. The highest rate and absorption were reached 3 to 9 h after the beginning of light period (12 h), which gradually decreased at 10 to 15 h after the beginning of light or dark period. The lowest rate and absorption was observed after the beginning of the dark period. The chloroplast movement was inhibited for 12 h by colchicine, and photosynthetic parameters were found to be dependent on various chloroplast positions in the thallus. Interestingly, the chloroplast moved to the surface and the side walls of the cells under continuous dark and light conditions, respectively, at approximately 48 to 72 h. However, decreased maximum quantum yield was observed under both continuous dark and light conditions.

中文翻译：

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低辐照度条件下长石Ul（Ulvaphyceae）的光合作用波动伴随叶绿体移位

在叶绿藻Ulva lactuca var中已知与叶绿体易位相关的光合特性的波动。拉蒂西马和瓦尔 根据光周期，选择刚硬和U. mutabilis。在乌尔瓦（Ulva），沿th体表壁发现了单个顶叶叶绿体，在光照期间表现出较高的光合作用活性。然后，叶绿体向侧壁移动，在黑暗时期显示出较低的光合作用活性。在这项研究中，我们重新研究了光合能力是否依赖于美国球藻的单藻培养物中的叶绿体位置。通过分析体内吸收光谱，氧气逸出和脉冲幅度调制叶绿素荧光，可以在低辐照度条件下生长并保持这种状态。叶绿体沿触角表面壁时的than光吸光度比沿侧壁时高，因此，将680nm处的all光吸收率用作叶绿体位置的指标。某些光合作用参数，例如每一个all的最大净光合速率和光系统II的有效量子产率与with的吸收率相关。亮期开始（12 h）后3至9 h达到最高吸收率和吸收率，亮期或暗期开始后10至15 h逐渐降低。在黑暗期开始后观察到最低的吸收率和吸收率。秋水仙碱抑制叶绿体的运动达12小时，并且发现光合参数取决于on体中叶绿体的不同位置。有趣的是，叶绿体分别在连续的黑暗和光亮条件下，大约在48至72小时内移动到细胞的表面和侧壁。然而，在连续的黑暗和光亮条件下都观察到最大量子产率降低。