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This study reports the widespread occurrence of foliar nectaries in most New World species of the genus Cyathea. The anatomy of these glands and the variation in structure among the species is described. Some Cyathea species primitively lack glands, and the presence or absence of these glands and their structure correlate with recent molecular phylogenies.
Ferns of the genus Marsilea (water clover) are potentially invasive aquatic and wetland plants. They are difficult to identify to species because of subtle diagnostic characters, the sterile condition of many specimens, and unresolved taxonomic problems. We sequenced four plastid regions (rbcL, rps4, rps4-trnS spacer, and trnL-F spacer) from 223 accessions across ca. 38 species. Our goals were to: 1) attempt to identify problematic Marsilea specimens from the southeastern U.S., and 2) assess species delimitation using molecular data. Florida specimens previously identified as M. aff. oligospora do not match true M. oligospora (native to the western USA), and might represent an undescribed native species. The molecular data fail to resolve many species as monophyletic within the New World Marsilea section Nodorhizae. The data reveal two strongly supported clades within section Nodorhizae: 1) A western U.S. /Mexican clade; and 2) A U.S. Gulf coastal plain/Florida/Caribbean clade. This DNA/morphology discordance suggests that these taxa either may have hybridized extensively or that the number of Marsilea species within these clades may be overestimated. Either case warrants the addition of nuclear data sets and reevaluation of the species boundaries within the genus.
Sixteen sites in China where Ceratopteris pteridoides occurs based on historical records and/or from observations were surveyed during preliminary field surveys. Eight previously recorded populations were found to have been extirpated. Decline in natural populations of C. pteridoides has resulted from the destruction or complete loss of its primary habitat. Analysis of 17 parameters of water quality indicated that differences in pH and dissolved oxygen might be principal factors determining the distribution and occurrence of C. pteridoides. The sites of the extirpated populations had higher water pH values than those of the sites of the extant populations (p < 0.05). The value of dissolved oxygen concentration at the sites of the extirpated populations was lower than at the sites of the extant populations (p < 0.05). The degeneration of primary habitats, a decline in the area of wetland coverage and deterioration of water quality caused by human activities are identified as the likely key factors responsible for the reduction in C. pteridoides populations. Because the habitat and population characteristics of eleven remaining populations were different, different sites should adopt different conservation methods as appropriate. Some small populations could be conserved by establishing conservation areas; other relatively large populations could be conserved by establishing nature reserves.
This study examined whether gravity influences the growth direction of dark-grown gametophytes of the fern Ceratopteris richardii. Analyses of directional growth of gametophytes in response to gravitropic stimulation demonstrated that gametophytes showed negative gravitropism. Dark-grown gametophytes of dkg1 her1 mutants, which germinate in complete darkness, displayed a more distinct negative gravitropism. Unlike her1 spores, dkg1 her1 spores do not require light irradiation to induce spore germination. Therefore, light irradiation on her1 spores was possibly inhibiting the negative gravitropism of her1 gametophytes. In the present study, prolonged white-light irradiation on her1 spores inhibited negative gravitropism in the gametophytes. Light irradiation on spores therefore affects the later negative gravitropism of dark-grown gametophytes.
The evolution of microorganism defense systems has led to intensive searches for new drugs extracted from various natural products to fight microbial infections. This study evaluated the antibacterial and antifungal activity of Lygodium venustum, a climbing fern. A phytochemical screening was performed using ethanol extract from leaves of L. venustum (EELV), detecting the presence of phenols, tannins, flavonoids and alkaloids. The test of Minimal Inhibitory Concentration (MIC) against Escherichia coli, Staphyloccocus aureus, Pseudomonas aeruginosa, Candida albicans, C. krusei and C. tropicalis was evaluated using the microdilution method, resulting in inhibitory concentrations ≥ 1024 µg/mL. Using a subinhibitory concentration of 128 µg/mL of EELV, the modulatory potential of the extract was tested against multidrug-resistant clinical isolates, resulting in synergism when combined with Gentamicin and actually altering the phenotype of S. aureus from sensitive to resistant. The extract also increased the effect of the kanamycin against S. aureus. This was the first report of modulatory antibiotic activity by a member of Lygodium.
A new species and a new hybrid in the genus Stenogrammitis are here described, and descriptions, illustrations, and comments on the most similar species are provided. Stenogrammitis brevipubens is characterized by having hemidimorphic laminae, with the fertile portion narrower and less dissected than the sterile portion, and by its indument, which is composed of simple, hyaline, and 2-celled hairs that are appressed upon the petiole, rachis, and laminar tissue. The hybrid, Stenogrammitis ×guatemalensis, has hemidimorphic laminae and reddish, 1-furcate and 3-celled hairs that are spreading on the petiole and lamina. Based on the hybrid morphology, the putative parents are S. prionodes and S. limula.
A new species, Diplazium fimbriatum (Athyriaceae), is described and illustrated. It is endemic to the humid montane forests of eastern Brazil, a region known for its high level of endemism and species richness. A comparative table to distinguish it from similar species of Diplazium occurring in Brazil is provided.
Isoetes mourabaptistae, a new species from southern Brazil, is described, illustrated, and compared to the most similar species. This new species is apparently restricted to southern Brazil, and is characterized by cristate to irregularly reticulate megaspores and microechinate microspores. It is an aquatic plant, occurring among submersed rocks along rivers, at about 900–1100 m in elevation.