抄録
Thlaspi caerulescens is known as a Cd hyperaccumulator, especially the ecotype of Ganges. However, the form of Cd in the shoots (mainly leaves) is unknown, and therefore was identified by using 113Cd-NMR spectrometry in the present study. Leaves enriched with 113Cd were prepared by exposing the roots to 113Cd(NO3)2 in a hydroponic culture. Measurements of 113Cd-NMR with intact leaves showed a signal at the chemical shift around -15 ppm. Crude leaf sap also gave a similar chemical shift. Purification by gel filtration (Sephadex G-10), followed by cationic and anionic exchange chromatography showed that only the anionic fraction gave the same chemical shift as intact leaves. Further purification of the anionic fraction, combined with 113Cd- and 1H-NMR studies revealed that only fraction mainly containing malate showed a chemical shift similar to the intact leaves. These results indicate that Cd coordinates with malate in the leaves of Thlaspi caerulescens.
