Morphometric analysis of cell wall sculpture in seven infraspecific taxa of Pediastrum boryanum (Sphaeropleales, Chlorophyta) and its taxonomic implications

Abstract

Ornamentation of the cell wall with special reference to granule density was evaluated as a taxonomic criterion for separating seven infraspecific taxa of Pediastrum boryanum (Turpin) Meneghini (Sphaeropleales, Chlorophyta). Twenty-two isolates from Danish lakes and three isolates from the culture collection in Göttingen (SAG) were studied by light microscopy and scanning electron microscopy. Granule density was measured on scanning electron micrographs, and a statistical analysis (ANOVA) showed the density to be a criterion of no value on its own. Its relationship with other distinguishing characters is discussed. It was concluded that identification of var. brevicorne A. Braun against var. boryanum is not possible, and the distinction between val. perforatum (Raciborski) Nitardy and var. cornutum (Raciborski) Sulek is questionable. The seldom recorded varieties val. pseudoglabrum Parra and var. forcipatum (Corda) Chodat can be recognized by cell wall sculpture alone. Based on cell wall sculpture, the SAG isolate of var. boryanum belongs to var. forcipatum. Variety longicorne Reinsch stands out by having the most constant set of characters and is the most easily recognized variety.