Sporoderm ultrastructure in Anthoceros agrestis Paton

Abstract

The sporoderm ultrastructure in Anthoceros agrestis Paton is unique. The wall of mature spores consists of granules varying in size and shape, and does not have any homogenеous or lamellar layers. The electron-lucent sporopollenin, which forms granules of the exosporium, is comparable to that in other spore-bearing plants (mosses, liverworts and Pteridophyta) in its electron density, while it is different in structure. Electron-dense substances in the gaps between the exosporium granules are resistant to acetolysis and are probably sporopolleninous. РезюмеСпородерма Anthoceros agrestis Paton характеризуется уникальной ультраструктурой. Оболочка зрелых спор построена из разнообразных по размеру и очертаниям гранул и не имеет гомогенных или ламеллятных слоев. Спорополленин основного, гранулярного, компонента оболочки по электронной плотности, но не по строению, сопоставим со спорополленином экзоспориев других споровых растений. Электронно-темные включения между гранулами основного компонента обо-лочки сохраняются после ацетолизной обработки спор и, вероятно, являются спорополленино-выми.

Conservation of Male Sterility 2 function during spore and pollen wall development supports an evolutionarily early recruitment of a core component in the sporopollenin biosynthetic pathway

“…The most basal land plant group, liverworts, do not have a perispore layer due to the apparent lack of a tapetum (Wellman, 2004). These structures are also absent in hornworts (Villarreal & Renzaglia, 2006;Polevova, 2012). The perispore layer is lost in the more recently evolved land plant groups (gymnosperms and angiosperms) which instead exhibit more complex and stratified exines, perhaps as a result of the perispore being incorporated into the exospore/exine over evolutionary time.…”