An X‐ray microanalytical examination of precipitation methods for the ultrastructural localization of potassium in plant tissue: I. Cobaltinitrite

In vitro and in vivo studies were carried out to assess the feasibility of adapting the cobaltinitrite method for the ultrastructural localization of K in plant cells. The relatively low mobility of the cobaltinitrite ion and the solubility of the precipitation product resulted in the formation of only a few large deposits in each cell. The addition of Ag at the time of precipitation was found to increase the number of small deposits retained in sections. However, cobaltinitrite reagents frequently caused plasmolysis and poor cytoplasmic preservation. Precipitation during freeze‐substitution was also attempted. It was concluded that precipitation of K using cobaltinitrite has only limited use in low magnification electron microscopy in conjunction with light microscopy. 1981 Blackwell Science Lt