Localization of copper accumulated in Rhynchostegium riparioides using sequential chemical extraction

A sequential chemical extraction procedure has enabled three fractions to be distinguished within the total copper (Cu) accumulated by the aquatic moss Rhynchostegium riparioides. These are (1) an intercellular fraction (Cu-res) located in the free-water space of the cell wall, (2) an exchangeable fraction (Cu-exch) which corresponds to metal trapped by exchange sites of the cell wall, and (3) a residual fraction (Cu-res) located within the cell itself. The procedure applied to this aquatic moss exposed to Cu under laboratory conditions showed the total Cu content of the moss at the end of the 21-day uptake phase to be 725 mu g g(-1). Fourteen percent of this was contributed by the Cu-res fraction, 47% by the Cu-int fraction and 39% by the Cu-exch fraction. At the end of the depuration phase, with a total Cu content in the moss of 293 mu g g(-1) the relative contribution of Cu-res reached 23% because the depuration of Cu concerned primarily the Cu-exch and, to a lesser extent, the Cu-int fractions, The fraction of the accumulated Cu that is not readily desorbed can be assumed to have penetrated the cytoplasm. (C) 1999 Elsevier Science B.V. All rights reserved.