Abstract
A gap in the exospore and the presence of a mesospore is found to be a normal part of development in the ten species ofSelaginella we have studied. The early spore wall consists of an exospore and a mesospore forming successively on the plasma membrane of the megaspore protoplast when it is 10–15 µm in diameter. Enlargement of the exospore and mesospore creates a central space, the lumen of the megaspore, around the megaspore protoplast. After that there is a vast enlargement of the exospore and a relatively small enlargement of the mesospore. The exospore splits close to its contact with the mesospore forming a gap over equatorial and distal regions. The gap becomes greatly expanded and becomes filled with lipids, PAS-positive carbohydrates, proteins and is crossed by wicks. Experiments with solutions of different osmolality on fresh megaspores show that the exospore and mesospore are not osmotic barriers. The mesospore appears not to be resistant to acetolysis at the many stages tested but exospore is resistant. Thus the mesospore size and shape is retained by the inner exospore that enveloped the mesospore. At maturation the mesospore undergoes lysis and absorption. At the beginning of germination stages an endospore forms at the inner part of the exospore. This inner part of the exospore, that adhered to and enveloped the mesospore, becomes pressed near to the bulk of the exospore. Until pregermination stages the megaspore protoplast is small (10–20 µm in diameter).
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Arnoldi W. (1896) Die Entwicklung des weiblichen Vorkeims bei den heterosporen Lycopodiaceen. Bot. Zeit. 54: 159–168.
Buchen B., Sievers A. (1978a) Megasporogenese vonSelaginella. I. Ultrastrukturelle und cytochemische Unter-suchungen zur Sekretion von Polysacchariden. Protoplasma 96: 293–317.
Buchen B., Sievers A. (1978b) Megasporogenese vonSelaginella. II. Ultrastrukturelle und cytochemische Untersuchungen zur Sekretion von Lipiden. Protoplasma 96: 319–328.
Buchen B., Sievers A. (1981) Sporogenesis and pollen grain formation. In: Kiermayer O. (ed.) Cell Biology Monographs 8. Springer, New York.
Campbell D. H. (1895) Structure and development of the mosses and ferns. Macmillan, London.
Campbell D. H. (1902) Studies on the gametophyte ofSelaginella. Ann. Bot. 16: 419–428.
Chamberlain C. J. (1932) Methods in plant histology. University of Chicago Press, 5th edn. 416 pp.
Denke P. (1902) Sporenentwicklung beiSelaginella. Beih. Bot. Centralbl. 12: 182–199.
Dumas C., Charriere-Ladreix Y. (1979) Étude cytochimique des polyphénols: généralités concernant les lignines et les sécrétions de tannins et d'aglycones flavoniques. Bull. Soc. Bot. France, Lett. bot. 126: 123–142.
Erdtman G. (1960) The acetolysis method. Svensk. Bot. Tidskr. 54: 561–564.
Fitting H. (1990) Bau und Entwicklungsgeschichte der Makrosporen vonIsoëtes undSelaginella und ihre Bedeutung für die Kenntniss des Wachstums pflanzlicher Zellmembranen. Bot. Z. 58: 107–165.
Heinsen E. (1894) Die Makrosporen und das weibliche Prothallium vonSelaginella. Flora Jena 78: 466–496.
Høeg O. A., Bose M. N., Manum S. (1955) On double walls in fossil megaspores. Nytt Mag. Bot. 4: 101–111.
Kempf E. K. (1971) Electron microscopy of mesozoic megaspores from Denmark. Grana 11: 151–163.
Lugardon B. (1987) Wall structure and mineral content inSelaginella spores. Pollen & Spores 20: 315–340.
Lyon F. M. (1901) A study of the sporangia and gametophytes ofSelaginella apus andSelaginella rupestris. Bot Gaz. 32: 124–170.
Lyon F. M. (1905) The spore coats ofSelaginella. Bot. Gaz. 40: 285–295.
Mettenius G. (1850) Zur Fortpflanzung der Gefässkryptogamen. Beitr. Bot. 1: 1–61.
Minaki M. (1984) Macrospore morphology and taxonomy ofSelaginella (Selaginellaceae). Pollen and Spores 26: 421–480.
Morbelli M. A. (1995): Megaspore wall in Lycophyta. Ultrastructure and function. Rev. Palaeobot. Palynol. 85: 1–12.
Morbelli M. A., Rowley J. R. (1993) Megaspore development inSelaginella. I. “Wicks”, their presence, ultrastructure and presumed function. Sexual Pl. Reprod. 6: 98–107.
Morbelli M. A., Rowley J. R. (1996) The gap and the mesospore inSelaginella megaspores. In: 9th International Palynological Congress, Houston, Texas, p. 111.
Pearse A. G. E. (1961) Histochemistry. Theoretical and applied, 2nd edn. Little, Brown and C Boston.
Pearse A. G. E. (1980) Histochemistry. Theoretical and applied. 1, Analytical technology. Churchill Livingstone, Edinburgh.
Pettitt J. M. (1966) Exine structure in some fossil and recent spores and pollen as revealed by light and electron microscopy. Bull. Brit. Mus. (Nat. Hist.), Geol. 13: 223–257.
Pettitt J. M. (1971) Development mechanisms in heterospory. I. Megasporocyte degeneration inSelaginella. Bot. J. Linn. Soc. 64: 237–246.
Pfeffer W. F. P. (1871) Die Entwicklung des Keimes der GattungSelaginella. Bot. Abhandl. Morphol. Physiol. 1: 1–80.
Pieniazek S. A. (1938) Über die Entwicklung und das Wachstum der Makrosporenmembranen beiSelaginella. Compt. Rend. Soc. Sci. Varsovie 31: 211–230.
Robert D. (1971a) Le gametophyte femelle deSelaginella kraussiana (Kunze) A. Br. I. Organization generale de la megaspore. Le diphragme et l' endospore. Les reserves. Rev. Cytol. Biol. Vég. 34: 93–164.
Robert D. (1971b) Le gametophyte femelle deSelaginella kraussiana (kunze) A. Br II. Organization histologique du tissu reproducteur et principaus aspects de la didiffer-enciation cellulaire preparatoire a l' oogenese. Rev. Cytol. Biol. Vég. 34: 189–232.
Roland J.-C., Lambi C. A., Morre J. (1972) Phosphotungstic acid-chromic acid selective electron-dense stain for plasma membranes of plant cells. Stain Technol. 47: 195–200.
Rowley J. R., El-Ghazaly G. (1992) Lipid in wall and cytoplasm ofSolidago pollen. Grana 31: 273–283.
Rowley J. R., Morbelli. M. A. (1995) Megaspore wall growth inSelaginella (Lycopodiatae). Plant Syst. Evol. 194: 133–162.
Sievers A., Buchen B. (1971) Contact between the spore cytoplasm and the growing sporoderm ofSelaginella megaspore. In: Brooks J., Grant P. R., Muir M., Van Gijzel P., Shaw G. (eds.) Sporopollenin. Academic Press, London.
Spurr A. R. (1969) A low-viscosity epoxy resin embedding medium for electron microscopy. J. Ultrastruct. Res. 266: 31–43.
Stainier F. (1965) Structure et infrastructure des parois sporales chez deux Selaginelles (Selaginella myosurus etS. kraussiana). Cellule 65: 221–344.
Stempak J. G., Ward R. T. (1964) An improved staining method for electron microscopy. J. Cell Biol. 22: 697–701.
Taylor W. A. (1989) Sporoderm ultrastructure in selected members of the genusSelaginella. Pollen and Spores 31: 251–288.
Taylor W. A. (1991) Ultrastructural analysis of sporoderm development in megaspores ofSelaginella galeottii (Lycophyta). Plant Syst. Evol. 174: 171–182.
Taylor W. A. (1994) Recognition and characterization of inner exospore wall layers in modern and fossil lycopsids — The mesospore. Grana 33: 44–48.
Taylor W. A., Taylor T. N. (1988) Ultrastructural analysis of selected Cretaceous megaspores from Argentina. J. Micropalaeont. 7: 73–87.
Thiéry J. P. (1967) Mise en évidence des polysaccharides sur coupes fines en microscopie. J. Microsc. 6: 987–1018.
Tryon A. F., Lugardon B. (1978) Wall structure and mineral content inSelaginella spores. Pollen et Spores 20: 315–340.
Tryon A. F., Lugardon B. (1991) Spores of thePteridophyta. Springer, New York.
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Morbelli, M.A., Rowley, J.R. Megaspore development inSelaginella The gap and the mesospore. Pl Syst Evol 217, 221–243 (1999). https://doi.org/10.1007/BF00984368
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DOI: https://doi.org/10.1007/BF00984368