Pteridium aquilinum (Dennstaedtiaceae), a Novel Hyperaccumulator Species of Hexavalent Chromium

Hexavalent chromium (Cr VI) is a highly toxic environmental pollutant produced as a byproduct of stainless steel manufacture and leather tanning. Several vegetal Cr VI-accumulating species have been investigated in phytoremediation, a promising technology to remove heavy metals from soils and water bodies. The aim of this work was to test the sensitivity, accumulation and remotion of Cr VI in both life cycle phases of the fern Pteridium aquilinum. Both gametophytes and sporophytes were obtained (in vitro) and evaluated (in vitro and using hydroponics) under controlled temperature, photoperiod and humidity conditions. One-month gametophytes were exposed in vitro to K2Cr2O7 (0, 50, 200, 600 and 800 µM). Four-month sporophytes were exposed to K2Cr2O7 (0, 800, 1600 and 6400 µM) under hydroponic conditions. Both phases were harvested at 24, 28, 72 and 168 h post-exposure, and biomass, chlorophyll content (a and b) and the amount of Cr in tissues and culture medium were tested. The results indicate that both phases of the cycle are not sensitive to Cr VI, since chlorosis and reduction in biomass were not observed. The gametophytes accumulated up to 915 mg of Cr×Kg−1 DW, while the sporophytes accumulated up to 11,854 of Cr×kg−1 DW in the underground parts. The sporophytes showed higher Cr uptake in rhizomes and adventitious roots, and despite having a low translocation index toward the leaves, these reached high concentrations as well (2240 mg Cr×Kg−1 DW). Given the uptake capacity in sporophytes, this fern places within the top five species with highest Cr accumulation, and it may be successfully used in phytoremediation methods.