Accumulation of Pb and Zn in Gametophytes and Sporophytes of the Moss Funaria hygrometrica(Funariales)

Abstract

Accumulation of lead and zinc was studied in the moss Funaria hygrometrica Hedw. collected from mine tailings. Heavy metal accumulation in gametophytes and sporophytes was quantified by graphite furnace atomic absorption spectrometry (GFAAS) and inductively coupled plasma-atomic emission spectrometry (ICP-AES). Pb and Zn accumulation in the placental zone was analysed by x-ray scanning electron microscopy (SEM) and transmission electron microscopy (TEM) microanalysis. Spectrometry showed that while moss gametophytes accumulated considerable concentrations of heavy metals, sporophytes accumulated only small concentrations of metals. X-ray SEM and TEM showed that the two metals accumulated in placental transfer cells on both the gametophytic and sporophytic sides. To investigate the uptake pattern for both metals under controlled conditions, F. hygrometrica plants collected from a non-polluted site were treated in the laboratory with separate solutions of Pb and Zn at two concentrations (10−2and 10−4M) for 24 or 168h. Metal accumulation was analysed separately in gametophytes and sporophytes using GFAAS and ICP–AES. Each generation had a different accumulation quotient for both metals, and gametophytes accumulated significantly more metal than sporophytes. Concentrations of Zn in sporophytes were always higher than concentrations of Pb. The findings are discussed in relation to the role performed by the gametophyte and the placenta in the accumulation and sequestration of Pb and Zn.