Species selection for phytoremediation of 36Cl/35Cl using angiosperm phylogeny and inter-taxa differences in uptake

High concentrations of 35Cl and the radioisotope 36Cl (produced naturally by cosmic radiation and anthropogenically by U fission and the use of neutron sources) can be problematic in soil, but are potentially amenable to phytoremediation if appropriate plants can be found. Here, results are reported that might aid the selection of plants with unusually high or low uptake of 36Cl A residual maximum likelihood analysis was used to estimate, from 13 experiments, relative 36Cl uptake by 106 species across the angiosperm phylogeny. Nested analysis of variance, coded using a recent angiosperm phylogeny, showed that there were significant inter-species differences in 36Cl uptake and that species behavior was not independent; but linked through theirphylogeny. Eudicots had significantly higher 36Cl uptake than Monocots and related clades and, in particular the Orders Caryophyllales, Apiales, and Cucurbitales had high uptake while the Poales, Lillales, Brassicales, and Fabales had low uptake. Overall, 35% of the inter-taxa variation in 36Cl was attributed to the taxonomic ranks of Order and above, a significant phylogenetic effect compared with other elements for which similar analyses have been published. The implications of these findings for selecting plants for phytoremediation of soil contaminated with 35/36Cl are discussed.