Distribution differences between ¹³⁷Cs and K in plant leaves

Concentrations of ¹³⁷Cs and ⁴⁰K in different aboveground perennial herbaceous plant and tree tissues, that is, leaf blade and petiole for giant butterbur, Japanese knot weed, ginkgo, Someiyoshino cherry and mochi tree were measured to clarify the distribution differences of these two elements. Other comparable tissue parts, that is, leaf and stem for Japanese knotweed, Canada goldenrod and field horsetail (fertile) were also studied. For ¹³⁷Cs, except mochi tree, concentrations in leaf blade and leaf parts were 1.1-6.0 times higher than those in petiole and stem parts. On the other hand, ⁴⁰K concentrations in leaf blade and leaf parts were 0.4-0.95 of those observed in petiole and stem parts. These results suggested that Cs and K did not behave similarly in these plants except for mochi tree, which is an evergreen tree. Thus, to understand the radiocesium fate in plants K measurement should not be used as analogue of Cs although Cs is known to have a similar chemical reactivity to that of K. (author)