Intake of Radionuclides in the Trees of Fukushima Forests 4. Binding of Radioiodine to Xyloglucan

Miki Nonaka,Oded Shoseyov,Takahisa Hayashi,Peter Capek,Rumi Kaida,Teruaki Taji,Yoichi Sakata,Chisato Yasukawa,Masaharu Tsubokura,Masateru Itakura,Shoko Aoki,Kei’Ichi Baba,Stefan Willför

doi:10.3390/f11090957

Abstract

The 1,4-linked glucans such as xyloglucan and amylose are known to form a complex with iodine/iodide ions and to also be precipitated with CaCl2 in the presence of iodine. Here, we show that iodine gas could be specifically incorporated into xyloglucan. Furthermore, we show that [125I]I2 gas is, over time, incorporated at high levels into the entire outer surface of poplar seedlings but that spraying seedlings with abscisic acid to close stomata decreases the incorporation of the gas. There was less incorporation of the gas in a transgenic poplar overexpressing xyloglucanase at the early stages when compared with a wild type. This shows that xyloglucan serves as a key absorber of iodine gas into a plant body. After individual leaves of cultured seedlings were exposed to the gas for 30 min, no radioiodine was emitted from those leaves over the following two weeks, indicating that no turnover occurs in radioiodine once it is bound to the polysaccharides in plant tissues. We conclude that forest trees could serve as one of the largest enormous capture systems for the radioiodine fallout following the nuclear power plant accident in Fukushima.

Highlights

The Fukushima Daiichi nuclear disaster on March 2011 caused the dispersal of high levels of radionuclides into the atmosphere, resulting in major environmental damage [1]
We show that xyloglucan serves as a key absorber involved in the response of forest trees to extreme exposure to radioiodine gas
The increased incorporation of radioiodine could be due to an increase in non intercalated xyloglucan via the hydrolysis of the amorphous regions of cellulose microfibrils

Summary

Introduction

The Fukushima Daiichi nuclear disaster on March 2011 caused the dispersal of high levels of radionuclides into the atmosphere, resulting in major environmental damage [1]. Among the major aerosol and volatile fission radionuclides, the most dangerous fallout could be that from the radioiodines, as exposure of the internal thyroid to them causes a thyroid cancer risk in children. Since the radioiodines have short half-lives, the period shortly after nuclear power plant accidents is the most dangerous. The radioiodines associated with Fukushima were mainly dispersed in a gaseous form, which has a slightly different deposition pattern from the aerosol form of radiocesium [3,4]. Nothing is known about radioiodine infiltration into forest trees, even though more than 90% of the rural land of Fukushima is forested. This paper reports the potential function of forest trees, based on the binding properties of radioiodine gas to xyloglucan

Objectives

Methods

Results

Conclusion