Uptake and Distribution of Iodine in Rice Plants

Inst. for Environmental Sciences, 1-7 Ienomae, Obuchi, Rokkasho-mura, Kamikita-gun, Aomori 039-3212, Japan.
Journal of Environmental Quality (Impact Factor: 2.65). 11/2008; 37(6):2243-7. DOI: 10.2134/jeq2008.0010
Source: PubMed


Rice (Oryza sativa L.) plants were cultivated in an experimental field and separated at harvest into different components, including polished rice, rice bran, hull, straw, and root. The contents of iodine in these components and the soil were determined by inductively coupled plasma-mass spectrometry and radiochemical neutron activation analysis, respectively. Iodine content varied by more than three orders of magnitude among the plant components. Mean concentration of iodine in the entire plants was 20 mg kg(-1) dry weight, and the concentration of iodine in the surface soil (0-20 cm depth) was 48 mg kg(-1). The highest concentration of iodine (53 mg kg(-1) dry weight) was measured in root and the lowest concentration (0.034 mg kg(-1) dry weight) in polished rice. While the edible component (polished rice) accounted for 32% of the total dry weight, it contained only 0.055% of iodine found in the entire rice plants. Atmospheric gaseous iodine (5.9 ng m(-3)) was estimated to contribute <0.2% of the total iodine content in the biomass of rice plants; therefore nearly all of the iodine in the rice plants was a result of the uptake of iodine from the soil. The content of iodine in the aboveground part of rice plants was 16 mg kg(-1) dry weight and the percentage of iodine transferred per cropping from the soil into the aboveground biomass corresponded to 0.27% (20 mg m(-2)) of the upper soil layer content.

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    • "Johnson (2003b) concluded that locally grown food from most areas of the world, except coastal areas, are not going to produce sufficient iodine to reach an Adults Recommended Dietary Allowance (RDA) of 150 lg day -1 . Iodine being non-mobile is not concentrated in the seed (Johnson 2003b), therefore, seed crops such as rice (and wheat) cannot be considered as a good source of dietary iodine (Fordyce et al. 2000; Tsukada et al. 2008). "
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