An arsenic-accumulating, hypertolerant brassica, Isatis capadocica

Abstract

Isatis capadocica, a brassica collected from Iranian arsenic-contaminated mine spoils and control populations, was examined to determine arsenate tolerance, metabolism and accumulation. • I. cappadocica exhibited arsenate hypertolerance in both mine and nonmine populations, actively growing at concentrations of > 1 mm arsenate in hydroponic solution. • I. cappadocica had an ability to accumulate high concentrations of arsenic in its shoots, in excess of 100 mg kg-1 DW, with a shoot : root transfer ratio of > 1. The ability to accumulate arsenic was exhibited in both hydroponics and contaminated soils. • Tolerance in this species was not achieved through suppression of high-affinity phosphate/arsenate root transport, in contrast to other monocotyledons and dicotyledons. A high percentage (> 50%) of arsenic in the tissues was phytochelatin complexed; however, it is argued that this is a constitutive, rather than an adaptive, mechanism of tolerance. © 2009 New Phytologist.