Variations in the Silica Content of Diatoms.

Investigations of the plankton diatoms in lakes and planktonic and epiphytic diatoms in cultures have shown that the silica content in the cells depends on the number of cells, and the silica content is inversely proportional to the number of cells. This is the case both in ordinary cultures where the Si-concentration and the concentration of other nutrient salts are decreasing when the number of cells increase and in cultures with a flowing culture solution. The decrease in the silica content is probably caused by diatoms giving off a substance to the water which inactivates the silica assimilation. [ABSTRACT FROM AUTHOR]