EFFECTS OF SELENIUM DEFICIENCY ON THE MORPHOLOGY AND ULTRASTRUCTURE OF THE COASTAL MARINE DIATOM THALASSIOSIRA PSEUDONANA (BACILLARIOPHYCEAE)1,2

Abstract

ABSTRACTThe effects of selenium deficiency on the siliceous and nonsiliceous components of the planktonic marine diatom Thalassiosira pseudonana (Hust.) Hasle and Heimdal (clone 3H) are examined using light and electron microscopy. Selenium deficiency induces elongation along the pervalvar axis initially as a result of chain formation caused by the failure of sibling cells to separate and subsequently by cell elongation via the production of hyaline girdle bands. In Se‐deficient cultures cell elongation involves the blockage of both mitotic and cytokinetic components of cell division. Selenium deficiency results in ultra‐structural alterations in the reticular membrane system and in mitochondrial and chloroplast membranes. Various types of inclusions are seen in vacuolar areas and the accumulation of lipid reserves is evident in Se‐deficient cells. These results provide indirect evidence for a metabolic Se requirement in this algal species.