SODIUM RELATIONS IN CHENOPODIACEAE - A COMPARATIVE APPROACH

Sodium relations of 15 species of Chenopodiaceae were studied in seedl ings grown on quartz sand at 10 mol m-3 of sodium and potassium. Uptak e of sodium and potassium into whole plants and shoots was followed ov er 2 weeks. High alkali ion uptake rates were found in all species. Th e apparent selectivity of alkali ion uptake showed a continuous variat ion between species, from nearly perfect sodium exclusion to negligibl e cation selection. K/Na ratios above 6 were found in the shoots of ei ght species. For most of these plants above ground sodium concentratio ns were highest in the hypocotyls. However, in Chenopodium hybridum (s hoot K/Na = 10) and C. urbicum (shoot K/Na = 17) above ground sodium c oncentrations were lowest in hypocotyls and highest in leaves, as in t hose species accumulating larger amounts of sodium. These differences are discussed with respect to the underlying mechanisms of ion regulat ion.