Abstract
Although iodine is not essential for plants, they take it up readily and, in foodchains, are significant sources of iodine for organisms with an essential requirement for it. During several nuclear accidents radioiodine has been an important component of releases of radioactivity and has caused serious contamination of foodchains. Differences in iodine uptake by different plant taxa are, therefore, important to nutritional and radioecological studies. Using techniques we have developed for a range of other elements, we analyzed inter-taxa differences in radioiodine uptake by 103 plant species and between varieties of two species, and analyzed them using a recent, phylogenetically-informed, taxonomy. The results show that there are significant differences in uptake above and below the species level. There are significant differences between Monocots and Eudicots in iodine uptake, and, in particular, hierarchical ANOVA revealed significant differences between Genera within Families. These analyses of the taxonomic origin of differences in plant uptake of iodine can help the prediction of crop contamination with radioiodine and the management of stable iodine in crops for nutritional purposes.
Highlights
Iodine (I) is readily taken up by plants if available [1], which is important to both agronomy and radioecology because, I is not an essential element for plants, food crops are a major conduit for the entry of I to human foodchains
Residual Maximum Likelihood (REML)-estimated relative mean I concentrations in 103 species of plants are shown in Table 1, which is the most taxonomically wide-ranging comparison of relative I concentrations in plants yet published
To enable comparison we estimated an overall concentration ratios (CRs) for radioiodine of 0.075 based on values for cereal stems and leaves, leafy vegetables and non-leafy vegetables (Table 17.1 in [19]). 125I activity values measured in the experiments for Figure 1 were transformed to have a geomean CR of 0.075
Summary
Iodine (I) is readily taken up by plants if available [1], which is important to both agronomy and radioecology because, I is not an essential element for plants, food crops are a major conduit for the entry of I to human foodchains. Soil-to-plant transfer factors can be quite low from, for example, Andosols with high anion exchange capacities [10], hydroponic experiments show that plants can take up large quantities of I if it is available to them [1] and most soils produce transfers to crops that can contribute significantly to food I content and to radiocontamination if 127I or 131/129I are available in the soil It has been suggested, based on a limited number of species, that inter-species differences exist in the plant uptake of I under comparative conditions (e.g., [10]) and concentrations of almost all elements across different plant species do not reflect soil availability, i.e., there are significant. The usefulness of the results to predicting the transfer of I isotopes from soils to plants in agricultural and radioecological contexts is discussed
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