Roleda Michael Y, Wiencke Christian, Hanelt Dieter, Bischof Kai
Biologische Anstalt Helgoland, Alfred Wegener Institute for Polar and Marine Research, Marine Station, Helgoland, Germany.
Photochem Photobiol. 2007 Jul-Aug;83(4):851-62. doi: 10.1562/2006-08-17-IR-1005.
The reproductive cells of macroalgae are regarded as the life history stages most susceptible to various environmental stresses, including UV radiation (UVR). UVR is proposed to determine the upper depth distribution limit of macroalgae on the shore. These hypotheses were tested by UV-exposure experiments, using spores and young thalli of the eulittoral Rhodophyceae Mastocarpus stellatus and Chondrus crispus and various sublittoral brown macroalgae (Phaeophyceae) with different depth distribution from Helgoland (German Bight) and Spitsbergen (Arctic). In spores, the degree of UV-induced inhibition of photosynthesis is lower in eulittoral species and higher in sublittoral species. After UV stress, recovery of photosynthetic capacity is faster in eulittoral compared to sublittoral species. DNA damage is lowest while repair of DNA damage is highest in eulittoral compared to sublittoral species. When the negative impact of UVR prevails, spore germination is inhibited. This is observed in deep water kelp species whereas the same UVR doses do not inhibit germination of shallow water kelp species. A potential acclimation mechanism to increase UV tolerance of brown algal spores is the species-specific ability to increase the content of UV-absorbing phlorotannins in response to UV-exposure. Growth rates of young Mastocarpus and Chondrus gametophytes exposed to experimental doses of UVR are not affected while growth rates of all young kelp sporophytes exposed to UVR are significantly lowered. Furthermore, morphological UV damage in Laminaria ochroleuca includes tissue deformation, lesion, blistering and thickening of the meristematic part of the lamina. The sensitivity of young sporophytes to DNA damage is correlated with thallus thickness and their optical characteristics. Growth rate is an integrative parameter of all physiological processes in juvenile plants. UV inhibition of growth may affect the upper distribution depth limit of adult life history stages. Juveniles possess several mechanisms to minimize UVR damage and, hence, are less sensitive but at the expense of growth. The species-specific susceptibility of the early life stages of macroalgae to UVR plays an important role for the determination of zonation patterns and probably also for shaping up community structure.
大型海藻的生殖细胞被视为生命史中对包括紫外线辐射（UVR）在内的各种环境胁迫最为敏感的阶段。UVR被认为决定了大型海藻在海岸带的上限深度分布。通过紫外线照射实验对这些假设进行了验证，实验使用了潮间带红藻星状美舌藻和皱波角叉菜的孢子及幼体，以及来自黑尔戈兰岛（德国湾）和斯匹次卑尔根岛（北极地区）不同深度分布的各种亚潮带褐藻（褐藻门）。在孢子中，紫外线诱导的光合作用抑制程度在潮间带物种中较低，而在亚潮带物种中较高。紫外线胁迫后，潮间带物种的光合能力恢复速度比亚潮带物种更快。与亚潮带物种相比，潮间带物种的DNA损伤最低，而DNA损伤修复能力最高。当UVR的负面影响占主导时，孢子萌发受到抑制。在深水海带物种中观察到了这种情况，而相同的UVR剂量并不会抑制浅水海带物种的萌发。一种提高褐藻孢子紫外线耐受性的潜在适应机制是，褐藻具有根据紫外线照射情况增加紫外线吸收性间苯三酚单宁含量的物种特异性能力。暴露于实验剂量UVR下的星状美舌藻和皱波角叉菜幼配子体的生长速率不受影响，而所有暴露于UVR下的海带幼孢子体的生长速率均显著降低。此外，黄海带的形态学紫外线损伤包括组织变形、损伤、起泡以及叶片分生组织部分增厚。幼孢子体对DNA损伤的敏感性与藻体厚度及其光学特性相关。生长速率是幼体植物所有生理过程的一个综合参数。紫外线对生长的抑制可能会影响成年生命史阶段的上限分布深度。幼体具有多种机制来最小化UVR损伤，因此敏感性较低，但代价是生长受到影响。大型海藻早期生命阶段对UVR的物种特异性敏感性在确定分带模式以及可能对塑造群落结构方面起着重要作用。
