A COMPARISON OF COMPUTERIZED IMAGE-ANALYSIS AND STEREOLOGY AS TOOLS FOR MORPHOLOGICAL-STUDY OF ALGAL CELLS

A computerized image analysis package (ImagePro+) was evaluated as an alternative method for morphometric analysis of electron micrographs o f microalgal cells. The morphometric analysis was demonstrated with mi crographs of the marine alga Nannochloropsis sp. grown under high and low light intensity. We applied the ImagePro+ package to estimate the relative volume of an organelle based on the ratio of perimeters of th e organelle and the cell. The measurements included the volumes of chl oroplasts, mitochondria, nuclei, vacuoles, and accumulation bodies, al l relative to cell volume. The length of thylakoids was measured using the same package. The results obtained by ImagePro+ were compared to those of the traditional manual and laborious method involving the sup erimposition of an array of short lines on the micrograph. A high corr elation between the methods was found. The following correlations were found for chloroplast, nucleus, and accumulation bodies: 0.96, 0.92, and 0.75, respectively. The correlation between length of thylakoids ( ImagePro+) and surface area of thylakoids (superimposition) was 0.82.