Submitted to: American Society of Plant Physiologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/1999
Publication Date: N/A
Technical Abstract: Hyperaccumulation of heavy metals is a constitutive trait in Thlaspi caerulescens. Of the various identified ecotypes, most hyperaccumulate Zn, often as high as 3% Zn DW, in the absence of phytotoxicity. Cadmium hyperaccumulation between ecotypes varies significantly, however, an observation which is counterintuitive, given that plants would be expected to treat Zn and Cd as analogs. Furthermore, as presented here, this variation in Cd hyperaccumulation is not related to the Cd content of the native soil from which each ecotype was collected. These observations suggest that there are unique physiological and/or biochemical differences in Cd transport and detoxification between these ecotypes. The primary goal of our research is to elucidate the mechanisms underlying these differences as a prelude to a molecular genetic approach to identify the genetic basis of these traits. The specific objectives of the current study were to: 1) characterize Zn and Cd accumulation by four Thlaspi ecotypes under controlled conditions; 2) examine the kinetics of Cd uptake and transport by the same ecotypes. Results from an initial hydroponic study confirmed that the ecotypes hyperaccumulated Zn, with three showing comparable levels of shoot Zn. The fourth, a newly identified ecotype, showed a two-fold greater accumulation of Zn. Cd accumulation differed between the four ecotypes, with the new Thlaspi ecotype again showing the greatest accumulation. 109Cd radiotracer flux studies are currently underway to characterize the unidirectional influx of this metal into roots of the four ecotypes and the time course of Cd accumulation into shoots. Results obtained from these experiments should aid in localizing and characterizing the observed differences in Cd accumulation.