苏铁属

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蘇鐵屬
Cycus tici.jpg
科學分類
界: 植物界 Plantae
門: Gymnospermae
綱: 蘇鐵綱 Cycadopsida
目: 蘇鐵目 Cycadales
科: 蘇鐵科 Cycadaceae
Pers.[1]
屬: 蘇鐵屬 Cycas
L.[2]
模式種
C. circinalis[2]
L.[2]

見下文

異名[3]
  • Todda-pana Adans.
  • Dyerocycas Nakai
  • Epicycas de Laub.

苏铁属生物分类学上是苏铁目苏铁科的唯一。苏铁,又称为铁树凤尾铁凤尾蕉,属于苏铁科。苏铁类植物是地球上现存最古老的种子植物,起源於古生代印度次大陸,迄今为止已有2.8亿年的历史。到侏罗纪白堊紀時期達至巔峰,遍及全球,成为恐龙的主要食物。及至白堊紀結束時,當非鳥類的恐龍都滅絕時,北半球大多數的蘇鐵類物種亦同時滅絕。 目前世界上蘇鐵屬有114種[4] ,其中大多数是在过去1200万年中的某个时候形成的[5] 。當中以蘇鐵Cycas revoluta)最廣為人知。

本屬物種分布南自澳洲東南亞一帶,北至中国南部和日本南部,在中国有15种铁树分布在八個省区内。 其中光果蘇鐵亦分佈在東非馬達加斯加

苏铁“Cycas”一词源于希腊文的椰子树名,苏铁类植物常被误认为棕榈树或是蕨类植物

苏铁类植物的精子有许多鞭毛,现生的种子植物中很少有这样的现象。

The genus is native to the Old World, with the species concentrated around the equatorial regions - eastern and southeastern Asia including the Philippines with 10 species (9 of which are endemic), eastern Africa (including Madagascar), northern Australia, Polynesia, and Micronesia. Australia has 26 species, while the Indo-Chinese area has about 30. India has 9 species. The northernmost species (C. revoluta) is found at 31°N in southern Japan. The southernmost (C. megacarpa) is found at 26°S in southeast Queensland. Due to the occurrence of large number of Cycas species in China and Australia, both the countries are considered as two centres of diversity of Cycas.[3]

A male cone of Cycas orixensis with unique forked microsporophylls
File:Rumphii1562.jpg
Bark of Cycas rumphii

The plants are dioecious, and the family Cycadaceae is unique among the cycads in not forming seed cones on female plants, but rather a group of leaf-like structures called megasporophylls each with seeds on the lower margins, and pollen cones or strobilus on male individuals.

Cycas media megasporophylls with nearly-mature seeds on a wild plant in north Queensland, Australia
Grove of Cycas media in north Queensland
Cycas platyphylla in north Queensland with new flush of fronds during the rainy season, still with glaucous bloom

The caudex is cylindrical, surrounded by the persistent petiole base. Most species form distinct branched or unbranched trunks but in some species the main trunk can be subterranean with the leaf crown appearing to arise directly from the ground. There are two types of leaves - foliage leaves and scaly leaves. The foliage leaves are pinnate (or more rarely bipinnate) and arranged spirally, with thick and hard keratinose. They are not permanent and fall off leaving back leaf-bases. The leaflets are articulated, have midrib but lack secondary veins. The scaly leaves are persistent, brown in colour and protective in function. Megasporophylls are not gathered in cones. Pollination takes place by air.

Often considered a living fossil, the earliest fossils of the genus Cycas appear in the Cenozoic although Cycas-like fossils that may belong to Cycadaceae extend well into the Mesozoic. Cycas is not closely related to other genera of cycads, and phylogenetic studies have shown that Cycadaceae is the sister-group to all other extant cycads.

The plant takes several years to grow, sexual reproduction takes place after 10 years of exclusive vegetative growth which occurs by bulbils arising at the base of the trunk.

A male cone of Cycas circinalis

Cycas species are threatened worldwide and almost all the species are listed in IUCN Redlist. Cycas beddomei is the only species of the genus Cycas listed in Appendix I of CITES. Cycas rumphii and Cycas pectinata have the most widespread distribution.

形态特征[编辑]

常绿棕榈状木本植物,茎高达5m.叶羽狀複葉,长达0.5~2.4m,厚革质而坚硬;羽片条状,长达18cm,边缘显著反卷。雄球花长圆柱形,小孢子叶木质,密被黄褐色绒毛,背面着生多数药囊;雌球花略呈扁球形,大孢子叶宽卵形,有羽状裂,密被黄褐色绒毛,在下部两侧着生2~4个裸露的直立胚珠。种子倒卵形或近球形,微扁,熟时橘红色。花期6~7月,种子10月成熟。

用途[编辑]

供观赏;种子有毒,誤食蘇鐵的種子會引起抽筋,嘔吐,腹瀉和出血等症狀。茎髓可采淀粉供食用;叶入药,性凉、味甘淡,功能散淤、止血,主治吐血、尿血、便血、月经过多、跌打肿痛等症。

物種[编辑]

参考文献[编辑]

  1. ^ Kramer, K.U.; (illustrations), P.S. Green ; assisted by E. Götz. Kramer, K.U.; Green, P.S, 编. Pteridophytes and Gymnosperms. Berlin: Springer-Verlag. 1990: 370. ISBN 978-3-540-51794-8. 
  2. ^ 2.0 2.1 2.2 Hill, Ken; Leonie Stanberg; Dennis Stevenson. The Cycad Pages. Genus Cycas. Royal Botanic Gardens Sydney. [6 September 2013]. 
  3. ^ 3.0 3.1 Kew World Checklist of Selected Plant Families
  4. ^ 蘇鐵科物種列表主頁面. [2016-07-24] (英文). 
  5. ^ Nagalingum, N. S.; Marshall, C. R., Quental, T. B., Rai, H. S., Little, D. P., Mathews, S. Recent Synchronous Radiation of a Living Fossil. Science. 2011-10-20. doi:10.1126/science.1209926. 
  6. ^ Micronesica40:169.

註腳[编辑]

外部連結[编辑]