Much of our understanding of root-microbe interactions derives from angiosperm studies where root microbiomes are likely driven by root exudates. Much less is known about the root microbiomes of seedless vascular plants even though this plant group evolved much earlier and was the first to develop roots. Single field horsetails (Equisetum arvense) and surrounding soils were collected from eight roadside sites in Erie County, Pennsylvania. Bacterial DNA was extracted from E. arvense roots and soil samples and the 16S rRNA V4 region was sequenced. Soil physio-chemical measures including pH, dissolved organic carbon, and ammonia content were determined at each site. Root and soil bacterial microbiomes were significantly different from one another, and both were significantly correlated with the soil physio-chemistry at each site. The three most abundant bacterial families on E. arvense roots, Streptomycetaceae, Comamonadaceae, and Chitinophagaceae, are well-known root microbes. There were nine core amplified sequence variants associated with E. arvense roots including four genera of nitrogen-fixing bacteria. These results suggest that the root bacterial microbiome of E. arvense is influenced by the environment, and that horsetail roots host bacterial communities that are separate from those in adjacent soil bacterial microbiomes. As with published studies of bryophyte rhizoids and spermatophyte roots, Proteobacteria, Actinobacteria, and Acidobacteria were highly abundant on E. arvense roots.

Staghorn ferns (Platycerium), ornamental ferns found across pantropical regions, reproduce primarily via spores in natural habitats. The geographical distribution of Platycerium species with varying climates could be linked to phylogeny. Temperature is crucial for spore germination, influencing the ecological niches of gametophytes and sporophytes. This study examined the thermal requirements for spore germination and the geographical distribution of 11 Platycerium species. Fresh spores were sown on a thermal gradient plate (10 to 37.5°C). Regression analysis determined the base (T_b), optimum (T_o), and maximum (T_m) temperatures for germination, as well as the thermal time (θ₅₀) needed for 50% of spores to germinate. The relationship between θ₅₀ and climate parameters in the species' natural habitats was also analyzed. Platycerium superbum and P. bifurcatum had T_b values of 9.5– 9.8°C, while other species ranged between 10.3–12.3°C. Platycerium madagascariense had the lowest T_o (27.3°C) and T_m (33.2°C), while others had T_o values of 28.8–30.6°C and T_m values of 34.9–36.9°C. Species from xeric environments had lower θ₅₀ values (50.6–58.4°Cd), while those from humid regions had higher θ₅₀ values (64.5–86.4°Cd). The cardinal temperatures of spore germination in staghorn fern species are related to their geographical distribution but are not consistent with their phylogenetic relationship. Species from regions with wet and dry seasons have lower θ₅₀ values, promoting spore germination and gametophyte growth during rainy seasons.

Ferns are an important part of many ecosystems, especially on islands, but are often overlooked in conservation priorities. Fern propagation can be challenging and requires significant time and resources, especially for rare ferns with limited propagation history. Some fern spores can survive for decades in the soil bank and some dry adapted ferns may store well at room temperatures for several years. Herbaria have been proposed as a source of viable propagules of rare plants for propagation. We explored herbarium specimens as a source of viable spores for conservation of rare and endangered Hawaiian ferns. We examined 156 herbarium specimens for the presence of spores and sampled spores from 50 of them spanning four decades. Germination of spores occurred in 24 specimens representing eight of nine included species within the 15-month experiment. However, gametophytes from spores from only five specimens (10%) representing three species (33%) produced sporophytes during the experiment. While fresh spores provide higher germination success, sporophytes developed from specimens of Pellaea ternifolia collected in 1984, 1989, and 2018, as well as from a specimen of Cyrtomium caryotideum from 2019 and a Doryopteris decora specimen from 2020. This result confirms that herbaria can be a source of dry adapted spores of rare species or populations that may be extinct or otherwise difficult to source. Increased attention on rare fern propagation techniques is critical to successful conservation efforts from both fresh and dried collections such as herbarium specimens.

In this study, we demonstrate the new base number of Histiopteris as x = 47, rather than previously reported x = 48, based on the observed chromosome numbers of 2n = 94 and 188 for Histiopteris incisa, representing the diploid and tetraploid states, respectively. Ploidy level analysis conducted in Japan reveals that all examined individuals of the “α” lineage, which is one of the two DNA lineages within this species, are tetraploid, whereas both diploid and tetraploid individuals are observed in the “β” lineage. Notably, tetraploid individuals of the β lineage are exclusively found in Yakushima, while diploid individuals are prevalent at other collection sites. Examination of herbarium specimens indicates that the localities of each DNA lineage of the specimens, which are identified based on morphological traits, correspond entirely to the localities of the α and β lineages of currently existing populations.