A SEM and light microscopy study of the oospore wall ornamentation in Polish charophytes (Charales, Charophyceae) - genus Chara

The taxonomic importance of oospore characters has long been recognized. Many authors believed such oospore characters to be constant and characteristic for each species and associated with the morphological characters that are useful taxonomically. The ornamentation can be helpful in taxonomy, if oospore ornamentation characters are conservative in nature, which is more common in the genus Nitella than in Chara. In the present investigation scanning electron microscopy (SEM) and, in few cases, light microscopy (LM) were used to study the oospore wall ornamentations of all species from the genera Chara that can be found in Poland. In case of several species (C. crassicaulis C. delicatula, C. filiformis and C. tomentosa), this study added new data on oospore wall ornamentation that had not been documented before. Based on new findings and other investigations of the oospore wall ornamentation, as well as using morphological characters of the species, taxonomic problems concerning many of the species investigated are discussed. Additionally, the relationship between length and width of several Chara species is also discussed in relation to its taxonomic significance. The presented study is the first on the ultrastructure of oospores for all the species from Chara that can be found in Poland, and one of the first on charophyte oospore characteristics at all.