CONCENTRATIONS OF INORGANIC IONS AS RELATED TO GROWTH OF EXCISED ROOT-TIPS OF WHEAT SEEDLINGS

Abstract

Using a Uspenski solution plus 2% dextrose and 0.01% extract of brewer''s yeast as standard, the conc. of the ions of the nutrient were varied singly and in pairs and the effects of these variations on growth of isolated wheat root-tips during a 2-week period studied. The following conclusions were drawn: That the medium could be improved by lowering the Ca content 50%. The standard K concentration was approximately optimal. In the presence of CO3 the Mg concentration was supra-optimal, but the best results were obtained by omitting CO3 and increasing the Mg concentration 50%. The Fe concentration of the standard solution was markedly sub-optimal. Ferric chloride and ferric citrate were unsatisfactory as sources of iron. Except for the marked detrimental effect of CO3, varying the concentration of the anions gave no consistent results. Solutions made up to contain each a single anion in preponderance but with standard concentrations and proportions of cations, showed nitrate solutions to be almost, though not quite, equal to the control although, surprisingly, varying the NO3 or NH4 content in the presence of all other ions, or omitting N2 entirely, gave no significant results. The work must be considered tentative only.