An SEM study of developmental variation in oospore wall ornamentation of three Nitella species (Charophyta) in Australia

Abstract

Oospore ornamentation in three species of Nitella (Charophyta) is investigated with reference to developmental stage. Australian populations of N. stuartii A. Braun possess characteristics identical to those reported for Indian material. Oospore characteristics of N. cristata A. Braun and N. pseudoflabellata A. Braun are described for the first time using SEM. Variation between oospores at different developmental stages on the same plant is greater than variation between mature oospores from different populations of the same species. The timing of development of the highly resistant oospore wall may be related to autecological similarities rather than to taxonomic affiliations. SEM may be used to confirm species determinations in spore-bank studies, as mature oospore wall characteristics were not significantly changed by residence in soil.