The uptake of potassium chloride by disks of several storage tissues has been determined from solutions at alkaline pH values and compared with that from 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 HCO,f anions present in alkaline solutions which generally promotes the uptake of cations ; tissues which do not show the 'pH effect' accumulate very little HC03~ 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 repre sents either a true pH effect or a direct effect of HCO7 anions on the overall salt accumulation mechanism rather than an indirect effect through organic acid synthesis. 4. The experiments reveal a cation/anion ratio of approximately 1:1 when the uptake of HCO7 ions is taken into consideration. It is suggested that this ratio may be more frequent than is generally accepted and that the uptake of C02 (converted to an anion in the tissue) may take the place of HCO7 ions at lower pH values. 5. The deleterious effects of HCO?~ frequently observed on growth contrast with the stimulations of salt absorption obtained here; the rapid increase in the concentration of cations and/or organic acid anions associated with HCO7 uptake may in some way be responsible for this.
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R. G. HURD (1959) studied this question.