Sporophyte Structure in the Neotropical Hornwort Phaeomegaceros fimbriatus: Implications for Phylogeny, Taxonomy, and Character Evolution
Sporophyte Structure in the Neotropical Hornwort Phaeomegaceros fimbriatus: Implications for Phylogeny, Taxonomy, and Character Evolution
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新热带金鱼藻 Phaeomegaceros fimbriatus 的孢子体结构：对系统发育、分类学和性状进化的意义
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
K. Renzaglia
中科院分区：
文献类型：
--
作者：
J. Villarreal A.;K. Renzaglia
本文首次详细描述了新热带金鱼藻的孢子体的结构。来自巴拿马、委内瑞拉、哥斯达黎加和厄瓜多尔的毛棕榈藻种群描述了胎座、基本分生组织和气生孢子体的形态和超微结构，该种鲜为人知但分布广泛。胎盘中有壁突起的配子体细胞和缺乏突起的吸器孢子体细胞紧密地混合在一起。通过倒斜分裂，基本分生组织产生一个原生真皮，几排同化细胞，以及围绕16个细胞的柱状细胞的单环原生孢子细胞。随着孢子体的伸长，孢子体进一步沿斜向分裂产生两排或三排的孢子母细胞，它们与较早的原始体混合在一起，两者分离并悬浮在粘液中。孢子细小蠕动，远端表面有7至10个凹陷。孢子壁由由孢子母细胞壁分化而来的类周壁外层、两层外壁和半透明内壁组成。外壁增厚和稀疏的孢粉沉积形成的孔洞定义了明显的三线标记。成熟的孢子体由长形厚壁具气孔的表皮细胞、造孢器、长达30个细胞的中央柱状细胞和7~13层同化细胞组成，叶绿体缺乏果核。这项研究揭示了委内瑞拉帕拉莫斯的植物与其他种群在形态上的明显分离，表明了最近的进化事件。孢子体的表面结构特征，如足部形状、孢子颜色和气孔，使其与棕榈藻一致，而更精细的组织学区域的发育，如大量的造孢组织和叶绿体的超微结构，表明它与巨藻有亲缘关系。棕藻和巨藻特征的独特混合定义了棕藻属，包括流苏藻，并提供了对角藻的分类和进化多样性的进一步评估。
The first detailed structural description of the sporophyte of a Neotropical hornwort is presented herein. The morphology and ultrastructure of the placenta, basal meristem, and aerial sporophyte are described in populations of Phaeomegaceros fimbriatus, a poorly known but widespread species, from Panama, Venezuela, Costa Rica, and Ecuador. Gametophyte cells with wall ingrowths and haustorial sporophyte cells lacking ingrowths are closely intermingled in the placenta. Through anticlinal divisions, the basal meristem generates a protoderm, several rows of assimilative cells, and a single ring of archesporial cells surrounding a columella of 16 cells. Further periclinal division in the archesporium produces two or three rows of spore mother cells intermixed with elater initials, both of which are separated and suspended in mucilage as the sporophyte elongates. Spores are finely vermiculate with seven to 10 dimples on the distal surface. Spore walls comprise a perine‐like outer layer derived from the spore mother cell wall, a two‐layered exine, and a translucent intine. An aperture of thickened exine and sparse sporopollenin deposition defines the conspicuous trilete mark. The mature sporophyte consists of elongated, thick‐walled epidermal cells with stomata, sporogenous tissue, a central columella of up to 30 cells, and seven to 13 layers of assimilative cells with chloroplasts lacking pyrenoids. This study reveals a sharp morphological separation of plants from Venezuelan paramos from the rest of the populations, indicating recent evolutionary events. Superficial structural features such as foot shape, spore color, and stomata in the sporophyte align P. fimbriatus with Phaeoceros, while more elaborate development of histological regions, such as massive sporogenous tissue and the ultrastructure of plastids, suggests affinities with Megaceros. The unique mixture of Phaeoceros and Megaceros traits defines the genus Phaeomegaceros, including P. fimbriatus, and provides further evaluation of the taxonomy and evolutionary diversification of hornworts.
影响因子：
10.7
作者：
Nickrent, DL;Parkinson, CL;Duff, RJ
通讯作者：
Duff, RJ