An Effect of pH and Bicarbonate on Salt Accumulation by Disks of Storage Tissue

1. The uptake of potassium chloride by disks of several storage tissues has been determined from solutions at alkaline pH values and compared with that form solutions at pH 6.5. The stimulation of cation uptake under the alkaline conditions which has previously been obtained with beet tissues was observed with some of these tissues to a greater or lesser extent. 2. It is concluded that it is the accumulation of $HCO3-$ anions present in alkaline solutions which generally promotes the uptake of cations; tissues which do not show the ‘pH effect’ accumulate very little $HCO3-$ in the presence of the Cl ^- anion. 3. In some cases the alkaline pH values also stimulated anion uptake. This was especially true in artichoke in which the absorption of both ions was stimulated by approximately the same amount. It is concluded that this represents either a true pH effect or a direct effect of $HCO3-$ anions on the overall salt sccumulation mechanism rather than an indirect effect through organic acid synthesis. 4. The experiments reveal a cation/anion ratio of approximately I:I when the uptake of $HCO3-$ ions is taken into consideration. It is suggested that this ratio may be more frequent then is generally accepted and that the uptake of CO ₂ (converted to an anion in the tissue) may take the place $HCO3-$ ions at lower pH values. 5. The deleterious effects of $HCO3-$ frequently observed on growth contrast with the stimulations of salt absorption obtained here; the rapid increase in the concertration of cations and/or organic acid anions associated with HCO uptake may in some way be responsible for this.