Renzaglia K S, Johnson T H, Gates H D, Whittier D P
Department of Plant Biology and Center for Systematic Biology, Southern Illinois University, Carbondale, Illinois 62901-6509 USA;
Am J Bot. 2001 Jul;88(7):1151-63.
In this correlated SEM (scanning electron microscope) and TEM (transmission electron microscope) investigation, we describe architectural details of the multiflagellated sperm cell of Psilotum nudum. Comparisons with other pteridophytes are made to (1) assess the placement of Psilotum among pteridophyte taxa and (2) evaluate structural modifications of sperm cells during land plant evolution. The released spermatozoid of Psilotum coils 2.0 revolutions and is outlined by a parallel band of up to 190 microtubules. The elongated nucleus is highly compacted and parallels the cellular coils with numerous mitochondria and starch-laden plastids distributed along its length. Along the anterior coil is an elaborate locomotory apparatus that includes ∼36 flagella that are inserted into the cell by basal bodies. Subtending the basal bodies is the multilayered structure, which consists of a long narrow lamellar strip and an overlying band of microtubules. An elongated anterior mitochondrion underlies the multilayered structure. Additional amyloplasts and mitochondria are aggregated along the anterior coil in association with the locomotory apparatus, while a fibrous band encircles the leading edge of the cell. Salient features of this cell, including details of the locomotory apparatus, structure and position of organelles, and arrangement of the spline, are shared by spermatozoids of Equisetum and ferns (including eusporangiate and leptosporangiate taxa). Thus, this study provides morphological support for the hypothesis that Psilotum nudum is a member of an assemblage that includes ferns and Equisetum. However, the less streamlined architecture of Psilotum gametes and the lack of architectural features shared with any specific taxon examined to date suggest that Psilotum is an early divergent fern, with relatively remote affinities to Ophioglossaceae and Equisetaceae.
在这项相关的扫描电子显微镜（SEM）和透射电子显微镜（TEM）研究中，我们描述了裸蕨多鞭毛精子细胞的结构细节。与其他蕨类植物进行比较，以（1）评估裸蕨在蕨类植物分类群中的位置，以及（2）评估陆地植物进化过程中精子细胞的结构变化。裸蕨释放的游动精子盘绕2.0圈，由多达190根微管组成的平行带勾勒出轮廓。细长的细胞核高度致密，与细胞盘绕平行，许多线粒体和充满淀粉的质体沿其长度分布。沿着前盘绕有一个复杂的运动装置，包括约36根鞭毛，这些鞭毛通过基体插入细胞。基体下方是多层结构，由一条长而窄的片状带和一条覆盖的微管束组成。一个细长的前线粒体位于多层结构之下。额外的造粉体和线粒体与运动装置一起沿着前盘绕聚集，而一条纤维带环绕着细胞的前缘。这种细胞的显著特征，包括运动装置的细节、细胞器的结构和位置以及花键的排列，与木贼和蕨类植物（包括厚囊蕨类和薄囊蕨类分类群）的游动精子相同。因此，本研究为裸蕨是包括蕨类植物和木贼在内的组合成员这一假说提供了形态学支持。然而，裸蕨配子的流线型结构较差，且缺乏与迄今研究的任何特定分类群共有的结构特征，这表明裸蕨是一种早期分化的蕨类植物，与瓶尔小草科和木贼科的亲缘关系相对较远。
