Morphological plasticity of the microscopic green alga Pseudopediastrum boryanum (Chlorophyceae) under varying nutrient concentrations
This study describes morphological changes of the genus Pseudopediastrum under varying nutrient concentrations. Three monoclonal strains representing P. boryanum var. boryanum, P. boryanum cf. var. forcipatum and P. boryanum var. longicorne were cultured in a Waris-H medium and its variants including a four-fold diluted and a three-fold concentrated ones. The number of cells in coenobia, the shape and size variation of marginal cells in the coenobia and the granule density of the cellular surface were investigated. The morphological changes occurred in both younger and older coenobia and they were strain-specific, except for similar trends of changes in the cell shape at the high nutrient concentration. Low nutrient concentration resulted in smaller cells and a low number of cells in the coenobia. The granule density was the most stable morphological feature, because it did not change significantly under any concentration of the culturing medium. The cell shape was the best diagnostic feature for the studied P. boryanum taxa, as it consistently allowed to discriminate between them regardless of the concentration of the nutrients.