Chara canescens part I: Oospore differentiation of parthenogenic and dioecious strains and salt-dependent oospore sizes

Chara canescens Loisel. is one of two European species of the section Desvauxia R.D. Wood of the genus Chara L. Whereas most populations of C. canescens reproduce parthenogenetically, a few sites with sexual reproducing populations are known. Studies of European C. canescens oospore morphology led to open questions about the taxonomic status. Here we investigated nearly 1000 oospores from 16 European populations originated from plant release, sediments, germination experiments and herbaria and two Asian populations resulting in a regional determination key for studied populations as well as important database implications regarding origin, oospore plant position and equipment used. The impact of salinisation on oospore morphology were tested by artificial salt levels. The longest but smallest oospores were formed at 3 PSU, whereas the widest at 0.1 PSU and the shortest at 5 PSU. Basal width and shape, on the other hand, seem to be only affected by higher salt contents. This study contributes the lacking oospore-information for both reproduction modes of European of C. canescens – populations.