The Uptake of Na22 by Intact Plants as Related to Root-to-Shoot Weight Ratio

Abstract

A laboratory study was made to investigate the time-course uptake of Na22 by intact plants. The time-course desorption of labeled sodium was also investigated after two exposure periods, while the uptake course in a bathing solution was going on. A significant relationship was obtained for the ratio of expected to actual values of uptake and desorption as a function of the root-to-shoot weight ratio. By expressing the activity on a per-gram fresh-weight root basis (specific activity) it appears that low values of root-to-shoot ratio are associated with greater than expected values of uptake and greater than expected values of desorption. The opposite is generally obtained with respect to extreme high values of the root-to-shoot ratio. The predominance of active transport as an accumulation mechanism is suggested when low root-to-shoot ratio values characterize the intact plants. High ratios would favor translocation by way of passive mass-flow along the transpiration stream.