THE ELEMENT COMPOSITION OF DIATOMS

The element composition of different-sized cells of the naturally occu rring diatoms Nitzschia sp. and Navicula sp. was analyzed by X-ray mic roanalysis under a JEM-100CX11 electron microscope equipped with an EM -ASID4D scanner and a LINK-860 X-ray microanalyzer with an E5423 detec tor. The relative contents of Mg, Si, P, S, Cl, K, and Ca were determi ned. The element composition of Navicula sp. cells varied depending on their size and differed from that of Nitzschia sp. These differences were most clearly seen from a comparison of the ratios of the major el ement Si to each of other elements studied. The relative contents of M g, P, S, and K suggest similar metabolic activity in the diatoms, wher eas the K/Ca ratio indicates possible growth deceleration and enhanced accumulation of reserve compounds in Nitzschia sp. cells and in the s mall cells of Navicula sp.