Gruber Ansgar, Roleda Michael Y, Bartsch Inka, Hanelt Dieter, Wiencke Christian
Biologische Anstalt Helgoland, Alfred Wegener Institute for Polar and Marine Research, 27498 Helgoland, GermanySection Functional Ecology, Department Seaweed Biology, Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, GermanyBiozentrum Klein Flottbek, University of Hamburg, Ohnhorst-Str. 18, 22609 Hamburg, GermanySection Functional Ecology, Department Seaweed Biology, Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany.
J Phycol. 2011 Jun;47(3):603-614. doi: 10.1111/j.1529-8817.2011.00998.x. Epub 2011 May 4.
To study the effect of different radiation conditions on sporogenesis of Laminaria digitata (Huds.) J. V. Lamour., excised disks were induced to form sporangia under PAR (P), PAR + ultraviolet-A (UVA) (PA), and PAR + UVA + ultraviolet-B (UVB) (PAB) conditions in the laboratory. Vitality of meiospores, released from sori induced under different radiation conditions in the laboratory and from sori of wild sporophytes acclimated to in situ solar radiation in the presence and absence of ultraviolet radiation (UVR), was measured in terms of their germination capacity. Sorus induction in disks of laboratory-grown sporophytes was not hampered under light supplemented with UVR, and sorus area was not significantly different among P, PA, and PAB. Vitality and germination rate of meiospores released from sori induced under different radiation treatments was comparable. Likewise, screening of UVR of the natural solar radiation did not promote higher germination rates of meiospores released from wild sporophytes. Germination rates were, however, higher in meiospores released from laboratory-induced sori compared to sori of wild sporophytes. Higher DNA damage (formation of cyclobutane pyrimidine dimers, CPDs) was observed in laboratory-grown nonsorus compared to sorus tissue, while CPDs were nondetectable in both sorus and nonsorus tissue of wild sporophytes. To explain the apparent protection of developing meiospores and the unexpected UV resistance of soral tissue, concurrent anatomical investigations of sporogenic tissue were performed. We observed the previously unreported existence of two types of sterile paraphysis cells. One type of paraphysis cells, the most frequent type, contained several red-fluorescing plastids. The other type, less frequently occurring, was completely filled with substances emitting blue fluorescence under violet excitation, presumably brown algal phenolic compounds (phlorotannins). Cells of this type were irregularly scattered within the sorus and did not contain red-fluorescing plastids. Meiospore-containing sporangia were positioned embedded between both types of paraphysis cells. In vegetative tissue, blue autofluorescence was observed only in injured parts of the blade. Results of our study suggest that the sorus structure with phlorotannins localized in the specialized paraphysis cells may be able to screen harmful UVR and protect UV-sensitive meiospores inside the sporangia.
为研究不同辐射条件对掌状海带（Huds.）J. V. Lamour.孢子形成的影响，在实验室中，将切除的圆盘组织在光合有效辐射（P）、光合有效辐射 + 紫外线A（UVA）（PA）和光合有效辐射 + UVA + 紫外线B（UVB）（PAB）条件下诱导形成孢子囊。从实验室不同辐射条件下诱导形成的孢子囊以及在有和无紫外线辐射（UVR）情况下适应原位太阳辐射的野生孢子体的孢子囊中释放的减数分裂孢子的活力，通过其萌发能力来测定。在补充了UVR的光照条件下，实验室培养的孢子体圆盘组织中的孢子囊诱导并未受到阻碍，并且在P、PA和PAB条件下孢子囊面积没有显著差异。不同辐射处理诱导形成的孢子囊中释放的减数分裂孢子的活力和萌发率相当。同样，对自然太阳辐射中的UVR进行筛选，也并未促进从野生孢子体释放的减数分裂孢子的更高萌发率。然而，与野生孢子体的孢子囊相比，从实验室诱导形成的孢子囊中释放的减数分裂孢子的萌发率更高。与孢子囊组织相比，在实验室培养的无孢子囊组织中观察到更高的DNA损伤（形成环丁烷嘧啶二聚体，CPDs），而在野生孢子体的孢子囊和无孢子囊组织中均未检测到CPDs。为了解释发育中的减数分裂孢子的明显保护作用以及孢子囊组织意外的抗紫外线能力，对孢子发生组织进行了同步解剖研究。我们观察到了两种类型的不育隔丝细胞，这是之前未报道过的。一种隔丝细胞是最常见的类型，含有几个发出红色荧光的质体。另一种类型较少出现，在紫光激发下完全充满发出蓝色荧光的物质，推测为褐藻酚类化合物（褐藻多酚）。这种类型的细胞不规则地散布在孢子囊内且不含有发出红色荧光的质体。含有减数分裂孢子的孢子囊位于两种隔丝细胞之间。在营养组织中，仅在叶片受伤部位观察到蓝色自发荧光。我们的研究结果表明，褐藻多酚定位于特殊隔丝细胞中的孢子囊结构可能能够筛选有害的UVR，并保护孢子囊内对紫外线敏感的减数分裂孢子。
