Phylogeny can be used to make useful predictions of soil-to-plant transfer factors for radionuclides

Soil-to-plant transfer of radionuclides can be related to plant evolutionary history (phylogeny). For some species and radionuclides the effect is significant enough to be useful in predicting Transfer Factors (TFs). Here a Residual Maximum Likelihood (REML)-based mixed model and a recent plant phylogeny are used to compile data on soil-to-plant transfer of radionuclides and to show how the phylogeny can be used to fill gaps in TFs. Using published data, generic means for TFs are used to anchor the data from REML modelling and hence predict TFs for important groups of plants. Radionuclides of Cs are used as an example. With a generic soil-to-plant TF of 0.07, TFs of 0.035 and 0.085 are predicted for monocot and eudicot gaps, respectively. Also demonstrated is how the known effects of soil conditions can be predicted across plant groups—predicted Cs TFs for gap-filling across all flowering plants are calculated for sandy loams with and without waterlogging. Predictions of TFs for Sr, Co, Cl and Ru are also given. Overall, the results show that general predictions of TFs based on phylogeny are possible—a significant contribution to gap filling for TFs.     

A cytostome/cytopharynx in green euglenoid flagellates (Euglenales) and its phylogenetic implications

The green, phototrophic euglenoid, Colacium libellae, has a vestigial cytostome and cytopharynx. The membrane forming the simple pocket is decorated with a dense, microfilamentous mesh. The mesh binds the pocket to a band of reinforcing microtubules which is homologous with the bodonid MTR. The opening of the cytostome at the reservoir-canal transition zone implies that the phototrophic euglenoid canal is formed by the invagination of the vestibulum of the phagotrophic euglenoids. Our observations support the hypothesis that the phagotrophic euglenoids arose from a bondonid ancestor and gave rise to the phototrophs by chloroplast acquisition.     

Chemical biology: Paper alert

A selection of interesting papers that were published in the two months before our press date in major journals most likely to report significant results in chemical biology.     

Assessing the Potential of Phytoremediation at a Site in the U.K. Contaminated With 137Cs

Spinacia oleracea L. cv. ‘Bloomsdale’, Beta vulgaris L. cv. ‘Flavescens’, Brassica juncea L. ‘OB825’, and Helianthus annuus L. cv. ‘Oranges and Lemons’ were grown for 8 weeks at a site contaminated with ¹³⁷Cs at Bradwell Nuclear Power Station, UK. The site was a trench approximately 1.5 m deep, 2 m wide, and 100 m long in ‘made ground’ consisting of alluvium with traces of illites, kaolinites, and smectites. ¹³⁷Cs activity concentration was measured in individual plants after 8 weeks growth and the soil in which they grew. The biomass produced and total ¹³⁷Cs removed to shoots differed significantly between species but ¹³⁷Cs activity concentrations and Transfer Factors (TFs) did not. B. vulgaris produced the most biomass and removed the greatest amount of ¹³⁷Cs. For all plants, and within each taxon, plants growing at low soil ¹³⁷Cs activity concentrations had significantly greater TFs than those growing at high soil ¹³⁷Cs activity concentrations. It is concluded that selecting plant taxa suited to a particular site can be an effective way of improving phytoremediation rates, that there is much scope for adjusting harvesting intervals to 8 weeks or less without affecting TFs, and that estimates of time taken for ¹³⁷Cs removal by phytoremediation should consider that TFs may increase as soil concentrations decrease. With refinements in methodology, phytoremediation has the potential to contribute significantly to decontamination of the site at Bradwell.