The subcellular concentration of ions and elements in thin cryosections of onion root meristem cells an electron-probe eds study

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Abstract
Quantitative electron-probe energy dispersive X-ray microanalysis has, for the first time, been accomplished at a subcellular level in plant tissue using cryofixed and thin freeze-dried cryosections. The subcellular concentrations of Na+, Cl−, K+, P, S, Mg2+ and Ca2+ were measured in mol/kg dry weight in two types of root meristematic cells of the onion, Allium cepa. The cell wall of the meristematic cells had much higher concentrations of K+ and Ca2+ than was found in the intracellular compartments. Storage granules in the protoderm cells were about 6-12 times lower in P and were about four times higher in S as compared to other intracellular compartments. Comparison between the concentrations of ions and other elements in meristematic plant cells and in mouse cardiac myocytes confirms that major differences in cytoplasmic Na+ and Cl− concentrations do indeed exist between these cell types.