Assessment of potentially toxic trace element contamination in urban allotment soils and their uptake by onions: A preliminary case study from Sheffield, England

Toxic trace element (TTE) contamination in urban soils may pose potential health risks, especially in cities with previous industrial activities. This study aimed to investigate soil contamination in urban allotments in Sheffield, the uptake of TTEs in autumn and spring sown onions (Allium cepa), and their potential risks on human health via consumption of the crops. Paired soil and plant samples were taken in triplicates from four private allotments to assess potentially elevated levels of lead (Pb), zinc (Zn), copper (Cu), arsenic (As), and chromium (Cr). These elements in soils exceeded the ambient background levels for England. Both Pb and As exceeded some UK and EU soil tolerable limits. Concentration factors (CF) were calculated as the ratio of trace element in the plant as compared to that in the soil, and uptake rates were in the order Zn>Cu>Cr>Pb>As. Concentrations were higher for most TTEs in spring sown onions (SSO), and had significantly higher CF (p < 0.05) for Pb and Cr than autumn sown onions (ASO), whereas the opposite was true for As. Toxic elements in plants did not exceed FAO/WHO intake limits when considering TTE content per plant and consumption rates. Human health risk assessment calculations using target hazard quotients (THQ) and hazard indexes (HI) indicated that consuming onions alone did not pose an immediate health risk

Investigating root architectural differences in lines of Arabidopsis thaliana. L. with altered stomatal density using high resolution X-Ray synchrotron imaging

Purpose Freshwater is an increasingly scarce natural resource, essential for agricultural production. As plants consume 70% of the world’s freshwater, a reduction in their water use would greatly reduce global water scarcity. Plants with improved Water Use Efficiency (WUE) such as those with altered expression of the Epidermal Patterning Factor (EPF) family of genes regulating stomatal density, could help reduce plant water footprint. Little however, is known about how this modification in Arabidopsis thaliana. L. affects root architectural development in soil, thus we aim to improve our understanding of root growth when stomatal density is altered. Methods We used X-Ray synchrotron and neutron imaging to measure in three dimensions, the root system architecture (RSA) of Arabidopsis thaliana. L. plants of three different genotypes, namely that of the wild type Columbia (Col 0) and two different EPF mutants, EPF2OE and epf2-1 (which show reduced and increased stomatal density, respectively). We also used the total biomass and carbon isotope discrimination (Δ) methods to determine how WUE varies in these genotypes when grown in a sandy loam soil under controlled conditions. Results Our results confirm that the EPF2OE line had superior WUE as compared to the wild type using both the Δ and total biomass method. The epf2-1 mutant, on the other hand, had significantly reduced WUE using the Δ but not with the biomass method. In terms of root growth, the RSAs of the different genotypes had no significant difference between each other. There was also no significant difference in rhizosphere porosity around their roots as compared to bulk soil for all genotypes. Conclusion Our results indicate that the EPF mutation altering stomatal density in Arabidopsis thaliana. L. plants did not have an adverse effect on root characteristics thus their wide adoption to reduce the global freshwater footprint is unlikely to compromise their soil foraging ability