Electron Microscopy of Replicas from Ultrasonicated Chara Oosporangial Walls

Abstract

Oosporangial walls from four populations of Chara zeylanica collected in Yucatan, Mexico, show similar ultrastructural features but differences occur in size and shape of papillae and in thickness of the outer wall. The inner walls have hollow papillae (ca. 1.5μ in diam) which are sometimes clustered. Ultrasonication at 27 kc for less than 5minutes separates the inner and outer wall and does not alter the surface morphology, but 30minute exposures erode the papillae. The outer wall commonly has an even, granulate surface, but when it is thinner it reflects the raised topography of the underlying papillae. From our findings we conclude that it is premature to adopt a complex terminology for wall stratification and surface morphology in the charophyte oosporangia until more is known regarding the range of variations and their control by genetic and environmental factors.