Translocation of Calcium. Exchange versus Mass Flow

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Abstract
A study was made of the influx via the roots of Ca45 labeled Ca into and the efflux from a specific portion of the stems of intact Red Kidney bean plants. Influx curves consisted of 2 phases, a reversible-exchange phase and a metabolic accumulation phase similar to the curves obtained in root studies. Efflux curves, as a result of the replacement of exchangeable Ca45 by nonlabeled Ca, were asymptotic in nature, as is typical of exchange reactions. Plants were also deprived of nutrient for 24 hours prior to experimentation in order to study further the exchange nature of Ca movement. The data indicated that the tracer Ca moved up the stem by a process of exchange. This concept of upward translocation in the plant stem is in controversy with the classical concept of mass flow.