Morphometric and Stereologic Analysis of Chlorella vulgaris Under Heterotrophic Growth Conditions

Abstract

A computer-supported determination of stereological paramelers was used to study the possible ultrastructural changes of Chlorella vulgairis UAM 101 under photolithotrophic, mixotrophic and photoheterotrophic conditions of growth. Data recording was carried out through a semi-automatic digitizing image analysis system instead of the current method of superimposition of an array of short lines. Glucose promoted drastic physiological changes [Martinez and Orus. 1991. Plant Physiology (in press)], which strongly affected the size of the cells and volume densities of storage materials. However, volumetric ratios of the mitochondrion or chloroplast active fraction were not affected by the presence of glucose, probably indicating that these ratios are characteristic of each species. Cell wall ultrastructure was also analysed and the presence of sporopollenin demonstrated, in contrast to the thin and sporopollenin-lacking cell wall generally described for Chlorella vulgaris species.