ACCUMULATION of most cations by higher plants is considered to be an aerobic process. However, we now find that sodium is in part an exception to this generalization. Uptake of sodium by 6-day old plants of Hordeum vulgare, variety Atlas 46, occurs under both aerobic and anaerobic conditions. Accumulation in the roots under anaerobic conditions is restricted to a period of about 2 hr. (Fig. 1), during which time transport to the shoots is almost nil (Fig. 2). The amount of sodium accumulated by plants the roots of which are in either aerobic or anaerobic solutions is inhibited by substances such as iodoacetate and methylene blue, indicative of the initial uptake being coupled to metabolic reactions in both cases rather than to passive processes. Non-steady-state uptake by the anaerobic plants, which decreases with time as if some process is attenuating, suggests that the reactions involving sodium uptake are several steps removed from the respiratory chain.