Arsenic uptake by arugula (Eruca vesicaria, L.) cultivars as affected by phosphate availability.

To assess the importance of variation among arugula (Eruca vesicaria subsp. sativa) cultivars in the ability to accumulate arsenic (As) in above-ground tissues, uptake of As by 16 cultivars was measured in the field and in hydroponic culture. In the field trial on soil contaminated by past pesticide use, As soil-plant uptake coefficients varied by a factor of 2.7 among different cultivars, approaching a value of one for the strongest accumulators. Compared to the field assay, hydroponically grown arugula accumulated much lower concentrations of As when nutrient solutions contained standard (high) concentrations of phosphate along with 1.0 mg L-1 As in the form of soluble arsenate. However, As accumulation was much greater in hydroponic culture using low-P nutrient solutions, an indication that phosphate strongly competed with arsenate for root uptake. Analysis of arugula roots after exposure to arsenate at 1.0 mg As L-1 and low phosphate revealed from 24 to 400 times greater As concentration in roots than tops, with S concentrations significantly greater in As-exposed than control roots. This indicated greater sulfate uptake by roots exposed to arsenate, and suggested that thiol-mediated As immobilization occurred in the roots which strongly restricted translocation to the tops.