SODIUM EXCLUSION BY CHENOPODIUM SPECIES

The uptake of sodium, potassium and chloride in Chenopodium album L. and Chenopodium schraderianum Roemer and Schultes was followed over 2 weeks. Ion concentrations and ion fluxes were compared to those observed in Atriplex prostrata Boucher ex DC. and Suaeda, maritima (L.) Dum. as halophilic Chenopodiaceae, and to Phaseolus aureus Roxb. and Trifolium alexandrinum L. as sodium-excluding Fabaceae. Seedlings of all species were cultivated in quartz sand at 10 mmol dm-3 of potassium. sodium, and chloride. For Fabaceae low uptake rates of alkali ions and sodium retention in roots are substantiated in Phaseolus. Results for Atriplex and Suaeda illustrate high uptake rates of alkali ions and preferential transport of sodium to the shoots. In contrast to halophilic chenopods, Chenopodium album and C. schraderianum show low sodium concentrations in shoots and a high K-Na-selectivity of net ion fluxes. Evidence for sodium exclusion by their roots is presented. Sodium exclusion by Chenopodium species is not as efficient as in Phaseolus, but is within the range of that found in other Fabaceae. Unlike other glycophytes, the Chenopodium species show the high rates of alkali ion uptake which have been found in their halophilic relatives.