Germinação de esporos e desenvolvimento gametofítico de Cyathea atrovirens (Langsd. & Fisch.) Domin (Cyatheaceae) em diferentes temperaturas e fotoperíodosSpore germination and gametophytic development of Cyathea atrovirens (Langsd...

Cyathea atrovirens (Langsd. & Fisch.) Domin (Cyatheaceae) é uma samambaia arborescente de ampla distribuição geográfica que ocorre no Nordeste, Centro-Oeste, 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 já estavam em estádio laminar aos 28 dias. Não houve germinação no escuro. As porcentagens de germinação e de gametófitos laminares foram igualmente altas em todos os fotoperíodos com presença de luz, variando de 91 a 97% e de 74 a 87%, respectivamente. Os dados obtidos podem contribuir para o entendimento da distribuição geográfica e da ocorrência de Cyathea atrovirens em diversos habitats.Abstract Cyathea atrovirens (Langsd. & Fisch.) Domin (Cyatheaceae) is a widely distributed arborescent fern, grown in the Northeast, Midwest, Southeast and South of Brazil, Paraguay, Argentina and Uruguay. The species is found in different environments such as forests, open areas and even in locations impacted by human action. The study aimed to evaluate the influence of temperature and the photoperiod on spore germination and on the gametophyte development of C. atrovirens. Spores were seeded in flasks containing liquid Meyer medium and maintained at temperatures of 15, 20, 23, 26, 29 and 32±1 ˚C (Experiment 1) and at photoperiod cycles of light and dark of 8, 12, 16, 24 h (Experiment 2). The highest germination percentages (84 to 99%) were observed at temperatures of 20 to 32 °C, while at 15 °C, 43% of the spores germinated. At 32 °C, most gametophytes still remained at the early stage, with chlorocyte and rhizoid (72%), whereas at temperatures from 20 to 29 °C, 61 to 73% of the gametophytes were already in laminar stage at 28 days. There was no germination in the dark. The percentages of germination and laminar gametophytes were equally high in all photoperiods with the presence of light, ranging from 91 to 97% and from 74 to 87%, respectively. The data obtained may contribute to the understanding of the geographical distribution and the occurrence of Cyathea atrovirens in diverse habitats

<b>Germination and gametophyte development of <i>Cyathea corcovadensis</i> (Raddi) Domin (Cyatheaceae) from spores stored at low temperatures

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

Abiotic environmental conditions for germination and development of gametophytes of Cyathea phalerata Mart. (Cyatheaceae)

ABSTRACT 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. The objective of this study was to assess the influence 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. The species produced its highest percentages of gametophytes in cultures with photoperiods between 6 and 18 h. The optimal abiotic conditions found here for in vitro development of C. phalerata are similar to those found in its natural habitat. The 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

In vitro spore germination and gametophyte development of two Cyathea species of South America in response to nutrient media

Abstract Cyathea corcovadensis and Cyathea phalerata are tree ferns native to Brazil, endangered in the state of Rio Grande do Sul. Spore germination and gametophyte development in media with different nutrient formulations and activated charcoal were evaluated, aiming to develop a process for obtaining plants of the two species. Spores were sown in four semi-solid culture media: Meyer, Dyer, MS with 50% and MS with 25% of the original macronutrient concentration. For each medium, 10 replicates were carried out (flasks with 5 mg of spores/30 mL of medium), with and without 1% activated charcoal, respectively. Spore germination and gametophytic development (laminar and cordate stages) were quantified at 30, 60 and 90 days of culture. Cyathea corcovadensis and C. phalerata germinated and developed gametophytes in all media. For both species, the highest percentages of germination and cordate gametophytes (more advanced development stage) were recorded in Meyer medium without activated charcoal, which has higher concentrations of macronutrients and no micronutrients compared to the other evaluated media. We recommend cultivating the plants in Meyer medium for greater gametophytic development and subsequent sporophyte obtention, as a biotechnological tool for C. corcovadensis and C. phalerata conservation and for environmental restoration and enrichment using these tree ferns