Biology
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Ferns are 'primitive' plants that spread by releasing spores rather than by producing flowers and fruits. The distinctive frond stage of the fern lifecycle is asexual; spores are released from the fronds, which then germinate into minuscule heart-shaped structures known as 'prothalli'. It is here that the sexual stage of the lifecycle occurs; male and female organs on the prothallus produce sperm and eggs respectively. If the female eggs are fertilised successfully, a new fern plant will begin to grow and the cycle starts again (4).
In Pteris adscensionis however, the sexual stage of the lifecycle does not occur and the spore-producing plant develops directly from the prothallus (4).
Conservation
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Ascension Conservation is carrying out vital cultivation of this species and is monitoring the highly vulnerable wild population (3).
Description
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This fern consists of bright green fronds that may form large tufts reaching up to 1 metre in height (2). The frond is divided into leaflets, which are themselves composed of smaller leaflets known as 'pinnules'. The spore-producing structures (known as 'sori') line both edges of the pinnule (2).
Habitat
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Cricket Valley is situated on the central mountain of Ascension Island (known as Green Mountain) at a height of 460 metres above sea level (3).
Range
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Endemic to Ascension Island in the south Atlantic, Pteris adscensionis is found mainly in Cricket Valley with a remnant population in Breackneck Valley (3). The total population is estimated to be no more than 200 plants (3).
Status
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Classified as Critically Endangered (CR – B1) in 2003 under IUCN Red List categories (3).
Threats
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Pteris adscensionis once constituted an important component of the vegetation of Ascension Island; this species has undergone a dramatic decline however, and is now absent from the summit of Green Mountain. Competition with introduced species is likely to be responsible for this decline (2). Today, populations are extremely reduced and Pteris adscensionis is thought to be the most threatened of Ascension's flora, with less than 200 plants remaining in the wild (3).
Pteris adscensionis
provided by wikipedia EN
Pteris adscensionis is a fern species in the subfamily Pteridoideae of the family Pteridaceae.[2] It is endemic to Ascension Island, and there are thought to be fewer than 500 individuals left in the wild. Its natural habitat has been severely reduced due to the large number of species introduced to the island when it was first settled in the 18th century.[1]
References
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Pteris adscensionis: Brief Summary
provided by wikipedia EN
Pteris adscensionis is a fern species in the subfamily Pteridoideae of the family Pteridaceae. It is endemic to Ascension Island, and there are thought to be fewer than 500 individuals left in the wild. Its natural habitat has been severely reduced due to the large number of species introduced to the island when it was first settled in the 18th century.
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Pteris adscensionis
(
Spanish; Castilian
)
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Pteris adscensionis: Brief Summary
(
Spanish; Castilian
)
provided by wikipedia ES
Pteris adscensionis es una especie botánica de helecho del género Pteris perteneciente a la subfamilia Pteridoideae en la familia Pteridaceae. Es un endemismo de la Isla Ascensión, en la que se cree que quedan poco más de 500 individuos en la vida silvestre. Su hábitat natural ha sido severamente reducido, debido al gran número de especies introducidas en la isla desde el siglo XVIII.
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Ptéris denté
(
French
)
provided by wikipedia FR
Pteris dentata
Le Ptéris denté ( Pteris dentata ) est une fougère de la famille des Pteridaceae et parfois classée parmi la famille des Adiantaceae selon les auteurs.
Description
- Période de sporulation : Juillet et Août.
- Mode de dissémination : anémochore.
Milieu de vie
Le Ptéris denté est une fougère des forêts tropicales.
Répartition géographique
Utilisations
Pas d'utilisation connue.
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Ptéris denté: Brief Summary
(
French
)
provided by wikipedia FR
Pteris dentata
Le Ptéris denté ( Pteris dentata ) est une fougère de la famille des Pteridaceae et parfois classée parmi la famille des Adiantaceae selon les auteurs.
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Pteris dentata
(
Vietnamese
)
provided by wikipedia VI
Pteris dentata là một loài thực vật có mạch trong họ Pteridaceae. Loài này được Forssk. miêu tả khoa học đầu tiên năm 1775.[1]
Hình ảnh
Chú thích
Liên kết ngoài
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Pteris dentata: Brief Summary
(
Vietnamese
)
provided by wikipedia VI
Pteris dentata là một loài thực vật có mạch trong họ Pteridaceae. Loài này được Forssk. miêu tả khoa học đầu tiên năm 1775.
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Datos: Q5489680
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