X‐ray Microanalysis of Phosphorus in Scenedesmus obtusiusculus

Abstract

AbstractResults from energy dispersive x‐ray microanalysis indicate considerable variation in phosphorus as well as in other elements found in polyphosphate granules in cells of Scenedesmus obtusiusculus starved of phosphorus for 24, 36 and 48 h. Comparison is made with cells at a 3‐h stage of synchronization and after 48 h cultivation in a phosphorus‐containing medium. After 48 h with a very limited external source of phosphorus, phosphorus was not detectable in‘polyphosphate granules’ in Epon‐Araldite sections unless the resin and other organic molecules were removed by plasma microincineration. In spite of the low amounts of elements (Mg. Al, Si, P and Ca) detected in these granules they are still dense to electrons in unstained sections, like the granules in cells cultivated in the presence of phosphorus. That suggests that the localized differences in the structural packing of elements or radicals in the polyphosphale polymer is more important For visualization of unstained polyphosphate granules than the absolute concentration of phosphorus or other elements. In contrast to previous assumptions, the abundance of morphologically‐observable‘polyphosphate’ granules can no longer be taken as an index of mobilizable phosphate reserves.