Kiss J Z, Swatzell L J
Department of Botany, Miami University, Oxford, OH 45056, USA.
J Microsc. 1996 Feb;181(Pt 2):213-21. doi: 10.1046/j.1365-2818.1996.107387.x.
Schizaea pusilla is a pteridophyte with several unique developmental characteristics. In contrast to most other fern species, S. pusilla gametophytes remain filamentous throughout their development, and the gametophytes are associated with an endophytic fungus which appears to be mycorrhizal. In terms of tropistic responses, apical filament cells of young gametophytes are negatively phototropic compared with germ filaments of other ferns which exhibit positive phototropism. Cryofixation (propane jet freezing and high-pressure freezing) in conjunction with freeze substitution electron microscopy was used to study young gametophytes. The results demonstrate that apical filament cells have a distinctive structural polarity and that rhizoids also can be successfully frozen by these methods. The cytoskeleton and endomembrane system were particularly well preserved in cryofixed cells. In addition, Schizaea gametophytes were used as a test system to evaluate potential artifacts of propane jet freezing and high pressure freezing. There was little apparent difference in ultrastructure between cells cryofixed by either freezing method. These gametophytes will be useful in determining the effectiveness of cryofixation techniques and as a model system in tip growth studies.
矮小裂叶蕨是一种具有若干独特发育特征的蕨类植物。与大多数其他蕨类物种不同，矮小裂叶蕨的配子体在整个发育过程中都保持丝状，并且配子体与一种似乎是菌根的内生真菌相关联。在向性反应方面，与表现出正向光性的其他蕨类植物的萌发丝相比，幼配子体的顶端丝细胞具有负向光性。采用冷冻固定（丙烷喷射冷冻和高压冷冻）结合冷冻置换电子显微镜来研究幼配子体。结果表明，顶端丝细胞具有独特的结构极性，并且根毛也能够通过这些方法成功冷冻。细胞骨架和内膜系统在冷冻固定的细胞中保存得特别完好。此外，矮小裂叶蕨的配子体被用作测试系统，以评估丙烷喷射冷冻和高压冷冻的潜在假象。两种冷冻方法冷冻固定的细胞之间的超微结构几乎没有明显差异。这些配子体将有助于确定冷冻固定技术的有效性，并作为顶端生长研究的模型系统。
