# _Pteridium equilibrium_ (Dennstaedtiaceae), a Novel Hyperaccumulator Species of Hexavalent Chromium  
[PERSON]  
1 Posgrado Ciencias Biomedicas, Instituto de Quimica, Universidad Nacional Autonoma de Mexico, Ciudad de Mexico 04510, Mexico; [EMAIL_ADDRESS] 1  
[PERSON]  
2 Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, Ciudad de Mexico 04510, Mexico  
species with potential to be applied in bioremediation processes is made in situ by analyzing the individuals that grow in locations highly polluted by heavy metals, which are included in bioassays [8]. The strategies to propose hyperaccumulator species are mainly based on bioassays under controlled conditions, such as in vitro cultures and hydroponic cultures. Both methods allow us to obtain information more readily than field experiments using the whole plant (root, stems and leaves). Furthermore, the experiments on cultures also allow us to modulate temperature, humidity, pH or photoperiod. Thus, it is possible to characterize the optimal growing parameters required by the studied plant [8].  
Regarding Cr VI, a plant is considered a hyperaccumulator if it is able to absorb above 0.1% of dry weight (DW) within its tissues [9] or if the plant concentrates above 0.1% of Cr DW into its leaves [10]. Currently, 70 known species of plants can absorb Cr; however, 90% of them fail to accumulate enough metal and cannot be considered hyperaccumulators, so these species do not meet the phytoremediation criteria [4]. Thus, the identification and description of new hyperaccumulator plants is crucial in the remediation of pollution through this biotechnological technique [4].  
Ferns are a promising group of plants in phytoremediation. Their life cycle shows alternations of heteromorphic and independent generations [11]: (I) a gametophyte phase with short-term prothallium that produces gametes and (II) a dominant sporophyte phase, represented by a corn constituted by root, stem and leaves with sporangia where meiospores are contained. When these meiospores germinate, they generate the prothallium [12]. In several fern species, it has been observed that both phases are hyperaccumulators and highly tolerant to heavy metals such as lead (Pb), arsenic (As) and Cr from polluted soils and water bodies [13; 14; 15].  
_Peteridium aquilinum_ (L.[PERSON] [PERSON] is a fern seconded to the Dennstaeditaaceae family, and it is a heliophile species and cosmopolite. It successfully grows in highly polluted ecosystems with nickel (Ni) and Cr [16; 17]. The presence of this plant in such habitats suggests it has the potential to be used in phytoremediation [18]. However, studies on its ability to accumulate Cr are lacking. Thus, the aim of this work was to determinate the accumulation capacity of _P. aquilinum_ in both gametophytes and sporophytes under controlled conditions by using both in vitro and hydroponic cultures.  
In order to characterize the accumulation capacity of Cr VI, both phases in the life cycle of this fern were exposed to increasing concentrations of the metal for different periods of time. The quantification of Cr VI was assessed through atomic absorption spectroscopy (ASS) using the flame method. The results indicate high accumulation from both sporophytes and gametophytes (11,973.93 mg Cr-Kg\({}^{-1}\) DW; 915 mg Cr-kg\({}^{-1}\) DW, respectively), where rhizomes and adventitious roots from sporophytes were the organs that showed the highest efficiency of accumulation, approximately 10-fold higher than the gametophytes. This taxon exhibits peculiar ecological and biochemical properties, such as having a considerable vegetative propagation, being an allelopathic, pioneer and heliophile plant and growing in highly perturbed and/or polluted zones. Considering these features along with the data obtained, this species meets the hyperaccumulator criteria and could be considered as a serious biotechnological tool in phytoremediation processes.