Roleda Michael Y, Wiencke Christian, Lüder Ulrike H
Biologische Anstalt Helgoland, Alfred Wegener Institute for Polar and Marine Research, Marine Station, Postfach 180, D-27483 Helgoland, Germany.
J Exp Bot. 2006;57(14):3847-56. doi: 10.1093/jxb/erl154. Epub 2006 Oct 18.
Stratospheric ozone depletion leads to enhanced UV-B radiation. Therefore, the capacity of reproductive cells to cope with different spectral irradiance was investigated in the laboratory. Zoospores of the upper sublittoral kelp Saccorhiza dermatodea were exposed to varying fluence of spectral irradiance consisting of photosynthetically active radiation (PAR, 400-700 nm; =P), PAR+UV-A radiation (UV-A, 320-400 nm; =PA), and PAR+UV-A+UV-B radiation (UV-B, 280-320 nm; =PAB). Structural changes, localization of phlorotannin-containing physodes, accumulation of UV-absorbing phlorotannins, and physiological responses of zoospores were measured after exposure treatments as well as after 2-6 d recovery in dim white light (8 mumol photon m(-2) s(-1)). Physodes increased in size under PAB treatment. Extrusion of phlorotannins into the medium and accumulation of physodes was induced not only under UVR treatment but also under PAR. UV-B radiation caused photodestruction indicated by a loss of pigmentation. Photosynthetic efficiency of spores was photoinhibited after 8 h exposure to 22 and 30 mumol photon m(-2) s(-1) of PAR, while supplement of UVR had a significant additional effect on photoinhibition. A relatively low recovery of photosystem II function was observed after 2 d recovery in spores exposed to 1.7 x 10(4) J m(-2) of UV-B, with a germination rate of only 49% of P treatment after 6 d recovery. The amount of UV-B-induced DNA damage measured as cyclobutane-pyrimidine dimers (CPDs) increased with the biologically effective UV-B dose (BED(DNA)). Significant removal of CPDs indicating repair of DNA damage was observed after 2 d in low white light. The protective function of phlorotannins has restricted efficiency for a single cell. Within a plume of zoospores, however, each cell can buffer each other and protect the lower layer of spores from excessive radiation. Exudation of phlorotannins into the water can also reduce the impact of UV-B radiation on UV-sensitive spores. The results of this study showed that the impact of UVR on reproductive cells can be mitigated by protective and repair mechanisms.
平流层臭氧损耗导致增强的UV-B辐射。因此，在实验室中研究了生殖细胞应对不同光谱辐照度的能力。将潮下带上层海带皮栖囊藻的游动孢子暴露于由光合有效辐射（PAR，400 - 700 nm；=P）、PAR + UV-A辐射（UV-A，320 - 400 nm；=PA）和PAR + UV-A + UV-B辐射（UV-B，280 - 320 nm；=PAB）组成的不同光谱辐照度通量下。在暴露处理后以及在昏暗白光（8 μmol光子 m⁻² s⁻¹）下恢复2 - 6天后，测量游动孢子的结构变化、含褐藻多酚的液泡体的定位、紫外线吸收性褐藻多酚的积累以及生理反应。在PAB处理下，液泡体尺寸增大。不仅在紫外线辐射处理下，而且在PAR处理下，都诱导了褐藻多酚向培养基中的挤出和液泡体的积累。UV-B辐射导致色素沉着丧失所表明的光破坏。在暴露于22和30 μmol光子 m⁻² s⁻¹ 的PAR 8小时后，孢子的光合效率受到光抑制，而紫外线辐射的补充对光抑制有显著的额外影响。在暴露于1.7×10⁴ J m⁻² 的UV-B的孢子中，在恢复2天后观察到光系统II功能的恢复相对较低，在恢复6天后发芽率仅为P处理的49%。以环丁烷嘧啶二聚体（CPDs）衡量的UV-B诱导的DNA损伤量随生物有效UV-B剂量（BED(DNA)）增加。在低白光下2天后观察到表明DNA损伤修复的CPDs显著去除。褐藻多酚的保护功能对单个细胞的效率有限。然而，在游动孢子羽流中，每个细胞可以相互缓冲并保护下层孢子免受过度辐射。褐藻多酚向水中的渗出也可以减少UV-B辐射对紫外线敏感孢子的影响。本研究结果表明，紫外线辐射对生殖细胞的影响可以通过保护和修复机制减轻。
