Inter-taxa differences in root uptake of 103/106Ru by plants

Ruthenium-106 is of potential radioecological importance but soil-to-plant Transfer Factors for it are available only for few plant species. A Residual Maximum Likelihood (REML) procedure was used to construct a database of relative 103/106Ru concentrations in 114 species of flowering plants including 106 species from experiments and 12 species from the literature (with 4 species in both). An Analysis of Variance (ANOVA), coded using a recent phylogeny for flowering plants, was used to identify a significant phylogenetic effect on relative mean 103/106Ru concentrations in flowering plants. There were differences of 2465-fold in the concentration to which plant species took up 103/106Ru. Thirty-nine percent of the variance in inter-species differences could be ascribed to the taxonomic level of Order or above. Plants in the Orders Geraniales and Asterales had notably high uptake of 103/106Ru compared to other plant groups. Plants on the Commelinoid monocot clades, and especially the Poaceae, had notably low uptake of103/106Ru. These data demonstrate that plant species are not independent units for 103/106Ru concentrations but are linked through phylogeny. It is concluded that models of soil-to-plant transfer of 103/106Ru should assume that; neither soil variables alone affect transfer nor plant species are independent units, and taking account of plant phylogeny might aid predictions of soil-to-plant transfer of 103/106Ru, especially for species for which Transfer Factors are not available.