Summary. At the end of a 4 hour absorption period approximately 95 % of the sodium absorbed by bean plants was retained in the secondary roots. The sodiumt translocated to the sihoot was retained in the stem.2,4-Dinitrophenol decreased the amnount retained in the secondary roots of bean plants and increased the amount translocated to the shoot. The stem retained most of the translocated sodium. Bean plants without roots absoribed considerably more sodium than plants with roots and translocated a greater proportion of the sodium to the -petioles and blades. 2,4-Dinitrophenol reduced the amount of sodium in the stem and petioles and inereased the amount in the blades.2,4-Dinitrophenol reduced the amount of sodium retained by the secondary roots of cotton plants but did not appreciably affect the amounts translocated to the shoot.The amount of sodium that plants absorb and tran4ocate to the shoot varies according to the species. Among 21 species 'grown on culture solutions containing equivalent amounts of sodium, potassium, and rubidium, 'Collander (6) found a wider range in the amount of sodium absorbed than in the amount of either potassium or rubidium absorbed. Other studies have indicated that bean (8,23), soybean and corn (13,14), and deciduous fruit and nut trees (1, 4, 11) transllocated very little sodiuim to the shoot, whereas beets (2, 3, 19) and cotton (5) readily translocated sodium to the shoot.Bower and Wadleiglh (3), using sand-resin mixtures adjusted to several levels of exchangeable sodium, and Lagerwerff and Holland (17), using culture solutions adjusted to 3 sodium-adsoriptionratios and 3 total-salt concentrations, found that sodium was translocated to the top of bean plants but only in the presence of high sodium concentrations in the medium. Jacoby (16) and Pearson (22) found that bean plants normally retained sodium in the basal portions of the stem but that sodium translocation was intcreased at higher external concentrations.Sodium translocation to bean shoots was also increased by 2,4-dinitroph,enol (DNP) (18,20,21). Thus, the restriction of sodium transport to the shoot of some species appears to be regulated, at least in part, by metabolism.With respect to beans, the inlcreased translocation of sodium to the shoot at h,ig,h external, concentrations or in the presence of an inhibitor might be anticipated if it is assumed that there is a reciprocal relationslhip between the amount of sodium retained in the root and the amounit translocated to the shoot. If such a recip(rocal relationship existed, sodium translocation to the shoot should be increased in the presence of a metabolic inhibitor as a result of decreased accumulation in the root. If it is assumed that roots have a strong afJfinity 'but a relatively smalli capacity for sodium, translocation to the shoot should be increased as the roots approach saturation with sodium.