Ultrastructural and cytochemical studies on spore development in Dryopteris erythrosora (Eaton) O. Ktze.

Spore development of Dryopteris erythrosora(Eaton) O. Ktze. was studied by transmission electron microscopy and cytochemical technology. Based on ultrastructural and cytochemical features, spore development was divided into three stages. (1) Spore mother cell and meiosis stage:sporocyte coat is formed at the late stage of the archesporial cells. The sporocyte coat covers the spore mother cells and the outer surface of the tetrads. The PAS reaction shows that this coat is polysaccharide in nature. It is an analogous structure with callose. During meiosis, spore coats are formed between the tetrad spores. The spore coats resemble the callose wall in function, formation site, and formation time. However, Sudan Black B staining shows that the spore coats may contain lipid material, which does not exist in the callose wall. (2) Exospore formation stage:exospore formation is Blechnoidal-type. The exospore consists of two layers, i.e. thin inner exospore and thick outer exospore. The former is composed of polysaccharides and the latter is composed of sporopollenin with a smooth outer surface. Globules participate in the formation of the outer exospore. Cytochemical staining shows that the center of the globules and inner part of the outer layer of the exospore are yellow, but the outer part of the globules and outer layer of the exospore became black when stained (probably containing lipids). It can be inferred that the globules and exospore develop simultaneously. (3) Perispore formation stage:perispore formation is Cavete-type. The perispore consists of an inner perispore and outer perispore. The thin inner perispore appresses the exospore closely. The outer perispore projects outwards and forms the outline of the ridge ornamentation of the spore. The development of the perispore is centripetal. Sudan Black and PAS reaction stain the perispore orange, indicating that the perispore may be composed of several polysaccharides. Spore wall cells participate in formation of the perispore. The present investigation provides new data for sporogenesis and spore wall development, which will contribute to revealing the cytological mechanism of sporogenesis.