Rincón Barón Edgar Javier, Forero Ballesteros Helkin Giovani, Gélvez Landazábal Leidy Viviana, Andrés Torres Gerardo, Hilda Rolleri Cristina
Grupo Semillero ecológico, Departamento de Biología, Calle 13 # 100-00, Universidad del Valle, Sede Meléndez, Cali, Colombia.
Rev Biol Trop. 2011 Dec;59(4):1845-58.
Studies on the ontogeny of the strobilus, sporangium and reproductive biology of this group of ferns are scarce. Here we describe the ontogeny of the strobilus and sporangia, and the process of sporogenesis using specimens of E. giganteum from Colombia collected along the Rio Frio, Distrito de Sevilla, Piedecuesta, Santander, at 2200m altitude. The strobili in different stages of development were fixed, dehydrated, embedded in paraffin, sectioned using a rotatory microtome and stained with the safranin O and fast green technique. Observations were made using differential interference contrast microscopy (DIC) or Nomarski microscopy, an optical microscopy illumination technique that enhances the contrast in unstained, transparent. Strobili arise and begin to develop in the apical meristems of the main axis and lateral branches, with no significant differences in the ontogeny of strobili of one or other axis. Successive processes of cell division and differentiation lead to the growth of the strobilus and the formation of sporangiophores. These are formed by the scutellum, the manubrium or pedicel-like, basal part of the sporangiophore, and initial cells of sporangium, which differentiate to form the sporangium wall, the sporocytes and the tapetum. There is not formation of a characteristic arquesporium, as sporocytes quickly undergo meiosis originating tetrads of spores. The tapetum retains its histological integrity, but subsequently the cell walls break down and form a plasmodium that invades the sporangial cavity, partially surrounding the tetrads, and then the spores. Towards the end of the sporogenesis the tapetum disintegrates leaving spores with elaters free within the sporangial cavity. Two layers finally form the sporangium wall: the sporangium wall itself, with thickened, lignified cell walls and an underlying pyknotic layer. The mature spores are chlorofilous, morphologically similar and have exospore, a thin perispore and two elaters. This study of the ontogeny of the spore-producing structures and spores is the first contribution of this type for a tropical species of the genus. Fluorescence microscopy indicates that elaters and the wall of the sporangium are autofluorescent, while other structures induced fluorescence emitted by the fluorescent dye safranin O. The results were also discussed in relation to what is known so far for other species of Equisetum, suggesting that ontogenetic processes and structure of characters sporoderm are relatively constant in Equisetum, which implies important diagnostic value in the taxonomy of the group.
关于这类蕨类植物孢子叶球、孢子囊的个体发育及生殖生物学的研究很少。在此，我们利用从哥伦比亚里奥弗里奥、塞维利亚区、皮德库埃斯塔、桑坦德采集的海拔2200米的巨型木贼标本，描述了孢子叶球和孢子囊的个体发育以及孢子发生过程。将处于不同发育阶段的孢子叶球固定、脱水、石蜡包埋，用旋转切片机切片，并用番红O和固绿技术染色。使用微分干涉差显微镜（DIC）或诺马斯基显微镜进行观察，这是一种光学显微镜照明技术，可增强未染色透明标本的对比度。孢子叶球在主轴和侧枝的顶端分生组织中产生并开始发育，在一个或另一个轴上的孢子叶球个体发育没有显著差异。细胞分裂和分化的连续过程导致孢子叶球的生长和孢子囊柄的形成。孢子囊柄由盾片、柄状或类似花梗的基部以及孢子囊的初始细胞形成，这些初始细胞分化形成孢子囊壁、孢子母细胞和绒毡层。没有形成特征性的原孢子细胞，因为孢子母细胞很快进行减数分裂产生四分体孢子。绒毡层保持其组织学完整性，但随后细胞壁分解形成原生质团，侵入孢子囊腔，部分包围四分体，然后包围孢子。在孢子发生接近尾声时，绒毡层解体，使带有弹丝的孢子在孢子囊腔内游离。孢子囊壁最终形成两层：孢子囊壁本身，具有加厚的木质化细胞壁和下面的固缩层。成熟孢子含叶绿素，形态相似，有外孢壁、一层薄的周壁和两条弹丝。这项对产孢结构和孢子个体发育的研究是该属热带物种的此类首次贡献。荧光显微镜显示弹丝和孢子囊壁自发荧光，而其他结构诱导由荧光染料番红O发出的荧光。还结合目前已知的其他木贼属物种的情况对结果进行了讨论，表明木贼属的个体发育过程和孢壁特征结构相对恒定，这意味着在该类群的分类学中具有重要的诊断价值。
