Influence of Chemical Forms on Iodine Uptake by Plant

Abstract

Uptake of iodide and iodate by komatsuna, Brassica Rapa var. pervidis, was studied using culture solution containing radioiodine as a tracer. After 24 hours'' exposure, accumulation of iodide in the plant was several times higher than that of iodate. The concentrations of both iodide and iodate in roots were much higher than those in shoots. It was estimated that high accumulation of iodide in roots was due to the adsorption of the element on the root surface. The plant of the earlier growth stage absorbed iodide selectively from the solution. On the contrary that of the older growth stage, more than 40 days after seeding, showed less absorption of the element.
Influence of stable iodine content on the uptake of radioiodine was also examined. The transfer rate of radioactive iodide to roots decreased remarkably with increasing amount of stable iodide in the culture solution, whereas that to shoots remained relatively constant indicating that the element content in shoots increased almost proportionally with the increasing concentration of stable iodine in the solution.
A significant amount of iodate in the culture solution was transformed to iodide in the presence of plant. The dominant chemical form of iodine in the plant was thought to be iodide.