In order to successfully establish themselves in their natural environment, ferns need habitats with abiotic conditions that are suitable for spore germination and gametophyte development. Th e objective of this study was to assess the infl uence of abiotic factors on the initial development of Cyathea phalerata cultivated in vitro. Spore germination and gametophyte development were assessed under varying conditions of surface sterilization, pH, temperature and photoperiod. Exogenous contamination was eliminated by sterilizing spores with 2.5 % NaClO for 15 min and sowing them into a culture medium supplemented with nystatin. Spores germinated at all pHs tested. Gametophytic development was faster in acidic pHs. Cultures at 25 °C exhibited the highest percentages of germination and laminar gametophytes. Th e species produced its highest percentages of gametophytes in cultures with photoperiods between 6 and 18 h. Th e optimal abiotic conditions found here for in vitro development of C. phalerata are similar to those found in its natural habitat. Th e southern limit of this species to north of the 30th parallel in Rio Grande do Sul, Brazil, may be because further south spores do not encounter the ideal combined conditions of temperature, pH and photoperiod determined in the laboratory.
The tree fern Cyathea corcovadensis (Raddi) Domin is an endangered species in the state of Rio Grande do Sul, Brazil. It currently occurs only in the northern segment of the coastal region. Spore storage would help in conservation programs since it maintains genetic variability and provides material for in vitro cultures. Current study evaluates the effect of low temperatures combined to different spore storage times on the germination and initial gametophyte development of C. corcovadensis. Spores were divided into two groups: spores of the first group were sowed immediately in Meyer culture medium with nystatin, at pH 4.0, while spores of the second group were stored at 7,-20 and-196°C during 60, 120, 180, and 365 days and then sowed in the same medium. Spore storage at 7 and-196°C for 365 days not only provided higher germination percentages than those reported for recently-collected spores but also stimulated gametophytic development. The latter was demonstrated by the higher percentages of laminar gametophytes in these treatments. The possibility of storing spores provides material for in vitro experiments, which is of special interest for C. corcovadensis due to its ornamental potential and conservation status.
ResumoCyathea atrovirens (Langsd. & Fisch.) Domin (Cyatheaceae) é uma samambaia arborescente de ampla distribuição geográfica que ocorre no Nordeste, CentroOeste, Sudeste e Sul do Brasil, no Paraguai, na Argentina e no Uruguai. A espécie habita ambientes diversos como florestas, áreas abertas e mesmo locais impactados pela ação humana. O estudo teve por objetivo avaliar a influencia da temperatura e do fotoperíodo na germinação de esporos e no desenvolvimento de gametófitos de C. atrovirens. Esporos foram semeados em frascos contendo meio de Meyer líquido e mantidos nas temperaturas de 15, 20, 23, 26, 29 e 32±1 ˚C (Experimento 1) e nos fotoperíodos de 8, 12, 16, 24 h de luz e no escuro (Experimento 2). As maiores porcentagens de germinação (84 a 99%) foram observadas nas temperaturas de 20 a 32 °C, enquanto que em 15 °C 43% dos esporos germinaram. Em 32 °C, a maior parte dos gametófitos ainda se encontrava em estádio inicial, com clorócito e rizoide (72%), enquanto que nas temperaturas de 20 a 29 °C, 61 a 73% dos gametófitos
A genotoxicidade do ar e a composição e estrutura comunitária de epífitos vasculares foram analisadas em um fragmento de mata ciliar inserido em uma unidade de conservação localizada na região metropolitana de Porto Alegre, no sul do Brasil. Durante cinco eventos distribuídos ao longo de um ano, inflorescências de Tradescantia pallida var. purpurea foram expostas por 8 horas ao ar atmosférico na borda do fragmento e micronúcleos foram quantificados em células meióticas. Foram registradas frequências de 4,07 a 5,27 micronúcleos, caracterizando o ambiente como genotóxico. Foram inventariadas 35 espécies de epífitos vasculares, alocadas em 22 gêneros e seis famílias. Orchidaceae, Bromeliaceae, Polypodiaceae e Cactaceae foram as famílias com maior riqueza (12, nove, seis e cinco espécies, respectivamente). Microgramma vacciniifolia, Rhipsalis teres, Tillandsia aeranthos e Pleopeltis pleopeltifolia, espécies com características adaptativas a ambientes com intervenções antrópicas, concentraram mais de 50% do valor de importância epifítico total da comunidade. A riqueza de espécies foi menor quando comparada às de matas ciliares do trecho superior da bacia hidrográfica em que se encontra a unidade de conservação. A simplificação da estrutura da comunidade epifítica pode estar associada ao aumento da urbanização e da poluição atmosférica evidenciada pela genotoxicidade do ar. Atmospheric Air Genotoxicity and Vascular Epiphytes in a Conservation Unit from a Metropolitan Area in South Brazil ABSTRACTThe genotoxicity of the atmospheric air and the community structure of vascular epiphytes were analyzed in a riparian forest fragment inserted in a conservation unit located in the metropolitan area of Porto Alegre, South Brazil. During five events along a year, inflorescences of Tradescantia pallida var. purpurea were exposed for 8 hours to the atmospheric air at the edge of the fragment and micronuclei were quantified in meiotic cells. Frequencies from 4.07 to 5.27 micronuclei were recorded, characterizing the environment as genotoxic. Thirty-five species of vascular epiphytes were inventoried, allocated in 22 genera and six families. Orchidaceae, Bromeliaceae, Polypodiaceae and Cactaceae were the families with the greatest richness (12, nine, six and five species, respectively). Microgramma vacciniifolia, Rhipsalis teres, Tillandsia aeranthos and Pleopeltis pleopeltifolia, species with adaptive characteristics to environments with anthropic interventions, concentrated more than 50% of the total epiphytic importance value of the community. Species richness was lower when compared to riparian forests at the upper stretch of the hydrographic basin where the conservation unit is located. The simplification of the structure of the epiphytic community may be associated with the increase in urbanization and atmospheric pollution evidenced by the genotoxicity of the air.Keywords: conservation, floristics, forest fragmentation, genotoxic potential, urbanization.
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