Holzinger A, Lütz C, Karsten U, Wiencke C
University of Innsbruck, Institute of Botany, Department of Physiology and Cell Physiology of Alpine Plants, Sternwartestrasse 15, 6020 Innsbruck, Austria.
Plant Biol (Stuttg). 2004 Sep;6(5):568-77. doi: 10.1055/s-2004-821003.
In radiation exposure experiments, the effects of mild artificial UV conditions (4.7 W m(-2) UV-A and 0.20 W m(-2) UV-B) plus PAR (25 - 30 micromol photons m(-2) s(-1)) on photosynthesis and ultrastructure of two red algal species from the Arctic have been investigated. While Palmaria palmata was collected from the upper sublittoral of the Kongsfjord (Spitsbergen, Norway), Odonthalia dentata represents a typical deepwater species at this high latitude. After 6 h and 24 h exposure to UV, chlorophyll fluorescence of photosystem II (PS II efficiency, F(v)/F(m)) was determined as an indicator for photosynthetic performance, and the relative electron transport rates in response to increasing photon fluence rates were recorded. In parallel, tissue samples were prepared for the transmission electron microscope (TEM). The presented data clearly demonstrate a significant influence of experimental UV on photosynthetic performance. Photochemical efficiency of PS II of both red algal species decreased to about one third of the initial value under UV. While the PI (photosynthesis-irradiance) curve parameter alpha (positive slope at limiting photon fluence rates) strongly decreased in both plants, the I(k) values (initial value of light-saturated photosynthetic rate) increased 3 - 5-fold. Palmaria palmata does not appear to become photoinhibited under these conditions, but O. dentata showed strong photoinhibition. The TEM results demonstrated that the photosynthetic apparatus was severely influenced by UV in both species, because thylakoid membranes appeared wrinkled, lumen dilatations occurred, and the outer membranes were altered. Moreover, mitochondria were damaged, and numerous plasma vesicles were observed. In conclusion, both red algal species are negatively affected by UV on the physiological and ultrastructural level. However, the differences in photoinhibitory responses correlate well with the vertical depth zonation of P. palmata and O. dentata in the Arctic Kongsfjord.
在辐射暴露实验中，研究了温和的人工紫外线条件（4.7 W m(-2)紫外线A和0.20 W m(-2)紫外线B）加上光合有效辐射（PAR，25 - 30微摩尔光子m(-2) s(-1)）对两种北极红藻光合作用和超微结构的影响。掌状红皮藻采自孔斯峡湾（挪威斯匹次卑尔根）潮下带上部，齿状齿丝藻是该高纬度地区典型的深水物种。在紫外线照射6小时和24小时后，测定光系统II的叶绿素荧光（PS II效率，F(v)/F(m)）作为光合性能的指标，并记录响应光子通量率增加的相对电子传递速率。同时，制备组织样本用于透射电子显微镜（TEM）观察。所呈现的数据清楚地表明实验紫外线对光合性能有显著影响。在紫外线照射下，两种红藻的PS II光化学效率均降至初始值的约三分之一。虽然两种植物的PI（光合作用-辐照度）曲线参数α（在极限光子通量率下的正斜率）都大幅下降，但I(k)值（光饱和光合速率的初始值）增加了3 - 5倍。掌状红皮藻在这些条件下似乎没有出现光抑制现象，但齿状齿丝藻表现出强烈的光抑制。TEM结果表明，两种藻类的光合装置都受到紫外线的严重影响，因为类囊体膜出现褶皱，腔室扩张，外膜发生改变。此外，线粒体受损，观察到大量的质膜小泡。总之，两种红藻在生理和超微结构水平上都受到紫外线的负面影响。然而，光抑制反应的差异与北极孔斯峡湾掌状红皮藻和齿状齿丝藻的垂直深度分布密切相关。
