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Acrostichum aureum is a halophytic pantropical invasive fern growing in mangroves and swamps. Its association with arbuscular mycorrhizal fungi (AMF) has been reported in Asia. AMF and their symbiosis (AM) commonly colonise the absorption organs of terrestrial plants worldwide. Furthermore, AMF/AM are well known for their capacity to bioaccumulate toxic elements and to alleviate biotic and abiotic stress (e.g., salinity stress) in their hosts. However, the mechanisms underlying AMF involvement in the halophytism of A. aureum and the structures where NaCl accumulates remain unknown. This study shows that A. aureum forms AM in margins of natural thermal ponds in Neotropical wetlands. All mature sporophytes were colonised by AMF, with high percentages for root length (ca. 57%), arbuscules (23), and hyphae (25) and low values for vesicles (2%). In A. aureum–AMF symbiosis, NaCl accumulated in AMF vesicles, and CaSO4 precipitated in colonised roots. Therefore, AM can contribute to the halophytic nature of this fern, allowing it to thrive in saline and thermal environments by capturing NaCl from fern tissues, compartmentalising it inside its vesicles, and precipitating CaSO4. [ABSTRACT FROM AUTHOR]

Background and aims: The plant's roots and fungi establish symbiotic endophytic associations that can coexist: arbuscular mycorrhizae and "dark septate" endophytes. Ferns and lycophytes are vascular plants that can form both fungal symbioses. The objective of this work is to detect the presence of fungal root endosymbiosis, know the mycorrhizal status, and analyze the type of colonizationin in native and ornamental ferns from the "Sierras Centrales de San Luis". M&M: In three sites in the "Sierras Centrales de San Luis", 9-10 individuals of each studied species were collected, their roots were processed to study these fungal. Characterization and quantification of their root colonization was evaluated. Results: In the three sites studied, Anemia tomentosa var. anthriscifolia formed mycorrhizal associations, the colonization presented abundant hyphal and arbusculated intracellular coils. In addition, glomoid spores of mycorrhizal fungi were found in their rhizospheres. Dark septate endophytes were absent in all species analyzed, none hyphae neither microsclerotia were recorded in roots of these native medicinal ferns. Conclusions: The mycorrhizal status of Anemia tomentosa var. anthriscifolia, one of the five medicinal fern species from the Sierras Centrales de San Luis studied, is presented. The arbuscular mycorrhizal colonization is described and quantified, and its type is determined as Paris. None of the fern species studied was associated with dark septate endophytes. [ABSTRACT FROM AUTHOR]