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多孢植物
化石時期：晚奧陶界 - 現代
Aglaophyton的復原圖，圖中顯示了其有終端孢子囊和假根的分叉軸。
科學分類 編輯
界： 植物界 Plantae
演化支： 鏈型植物 Streptophyta
演化支： 膜生植物 Phragmoplastophyta
演化支： 有胚植物 Embryophyta
演化支： 多孢植物 Polysporangiophyta
Kenrick & Crane (1997)
演化支

多胞植物（英語：Polysporangiophytes，也称polysporangiates或Polysporangiophyta），指的是在孢子體階段有終止在孢子囊的分支的莖（軸）的植物。學名的意思即為有許多孢子囊的植物。演化支包含所有陸地植物（有胚植物），但孢子體不分支的苔蘚植物（苔類、蘚類和角苔綱）除外。此外有另外一種定義是指有獨立的維管組織存在的植物，即維管植物，因為現存的所有多胞植物都有維管組織。但現已探明古多胞植物沒有維管組織，不屬於維管植物。

早期的多胞植物[編輯]

發現的歷史[編輯]

古植物學家將微化石與大化石區分開來。微化石主要是單個或成組孢子。而大化石保存的植物體的部分已經足夠大，可以展示植物體的結構，例如莖的截面或分支模式。[1]

道森，一位加拿大地質學家和古生物學家，最早發現和描述了多胞植物的大化石。1859年，他發表了一幅泥盆紀植物的復原圖，收集自一枚來自加拿大加斯帕地區的化石, 並命名為Psilophyton princeps。重建圖顯示水平和直立的莖狀結構；沒有葉或根。豎直的莖或軸分支分佈，附着着形成孢子的器官（孢子囊）。豎直軸上的橫截面顯示維管組織已經出現。他後來又描述了其他標本。道森的發現最初幾乎沒有科學影響；泰勒等人推測有可能是因為他重建的看起來很不尋常，並且化石年代實際比預期的的要古老。[2]

從1917年開始，Robert Kidston和William H. Lang發表了一系列的論文，描述了從萊尼燧石（一種在蘇格蘭阿伯丁郡的萊尼村附近發現的細顆粒沉積岩，現在確認它的年代是早泥盆世的布拉格期（約Template:Period span/brief））中發現的古植物。這些化石比道森的保存得更完好，清楚地顯示了這些早期陸生植物確實包括一般垂直裸莖，且呈現類似水平結構。豎直的莖分佈有頂端有孢子囊的分支。[2]

自此之後，在世界各地都在從志留紀到中泥盆世的地層中發現了類似的大化石，包括加拿大北極地區、美國東部、威爾斯、德國萊茵蘭、哈薩克斯坦、中國新疆和雲南以及澳大利亞。[3]

分類[編輯]

多胞植物的概念最早是由Kenrick和Crane在1997年提出的。[4]（右邊的分類代表他們對多胞植物的分類觀點。）該演化支的定義特徵是多個孢子體分叉，且承擔多個孢子囊。由此可將多胞植物與地錢、苔蘚和角苔等具有不分叉孢子體且每個孢子體只有一個孢子囊的植物區別。 多胞植物可能有也可能沒有維管組織——具有維管組織的屬於維管植物。

在此之前，大多數早期的多胞植物被放置在一個單獨的目中，即在裸蕨綱中的裸蕨目，於1917年由Kidston和Lang創立。[5] 現存的松葉蕨有時被放入此綱，也通常被稱為裸蕨類。[6]

隨着發現和描述了更多的化石，確認了它與裸蕨植物是不同的植物類群。1975年，Banks詳述了他早先在1968年將其分為三組的提議 ，並將其放在演化支的分類級別。[7][8]這些類群被分為門、[9]綱、[10]和目。[11]使用了許多種名稱，如下表所示。

Banks給三組選擇的名稱
門 演化支 綱 目 非正式命名
Rhyniophyta Rhyniophytina Rhyniopsida (Rhyniophytopsida)[12] Rhyniales rhyniophyte
Zosterophyllophyta Zosterophyllophytina Zosterophyllopsida Zosterophyllales zosterophyll (zosterophyllophyte)
Trimerophyta (Trimerophytophyta)[13] Trimerophytina (Trimerophytophytina) Trimeropsida (Trimerophytopsida) Trimerophytales trimerophyte

對Banks來說，萊尼蕨終端組成了簡單的無葉植物的孢子囊（例如頂囊蕨、萊尼蕨）with centrarch xylem; zosterophylls comprised plants with lateral sporangia that split distally (away from their attachment) to release their spores, and had exarch strands of xylem (e.g., Gosslingia). Trimerophytes comprised plants with large clusters of downwards curving terminal sporangia that split along their length to release their spores and had centrarch xylem strands (e.g., Psilophyton).[14]

Research by Kenrick and Crane that established the polysporangiophytes concluded that none of Banks' three groups were monophyletic. The rhyniophytes included "protracheophytes", which were precursors to vascular plants (e.g., Horneophyton, Aglaophyton); basal tracheophytes (e.g., Stockmansella, Rhynia gwynne-vaughanii); and plants allied to the lineages that led to the living club-mosses and allies as well as ferns and seed plants (e.g., Cooksonia species). The zosterophylls did contain a monophyletic clade, but some genera previously included in the group fell outside this clade (e.g., Hicklingia, Nothia). The trimerophytes were paraphyletic stem groups to both the crown group ferns and the crown group seed plants.[15][16]

許多研究人員敦促謹慎地對早期多胞植物分類。Taylor et al. note that basal groups, such as early land plants, are inherently difficult to characterize since they share many characters with all later-evolving groups (i.e., have multiple plesiomorphies).[9] In discussing the classification of the trimerophytes, Berry and Fairon-Demaret say that reaching a meaningful classification requires "a breakthrough in knowledge and understanding rather than simply a reinterpretation of the existing data and the surrounding mythology".[17] Kenrick and Crane's cladograms have been questioned – see the Evolution section below.

截至2011年2月 (2011-02)，儘管Cantino等人發表了Phylocode分類，根據Kenrick和Crane對進化枝的分析和後續研究似乎還是沒有完成對早期多胞植物的林奈法分類。[18] Banks的三組分類由於其便利被沿用至今。[9]

種系發生[編輯]

1997年，Kenrick和Crane發表了對主要的陸地植物演化支的研究，建立了多胞植物的概念和系統發生的概括。[4] Since 1997 there have been continual advances in understanding plant evolution, using RNA and DNA genome sequences and chemical analyses of fossils (例如Taylor等人2006[19]), resulting in revisions to this phylogeny.

In 2004, Crane et al. published a simplified cladogram for the polysporangiophytes (which they call polysporangiates), based on a number of figures in Kenrick and Crane (1997).[5] Their cladogram is reproduced below (with some branches collapsed into 'basal groups' to reduce the size of the diagram). Their analysis is not accepted by other researchers; for example Rothwell and Nixon say that the broadly defined fern group (moniliforms or monilophytes) is not monophyletic.[20]

polysporangiophytes
 

† 羊角蕨綱 (Caia、羊角蕨、Tortilicaulis)

 
 
 

† Aglaophyton

 
維管植物
 

† Rhyniaceae (Huvenia, Rhynia, Stockmansella)

 
 
 

† basal groups (Aberlemnia caledonica [=Cooksonia caledonica], Cooksonia pertoni)

 
 

Template:Clade panlycophyte

 
euphyllophytes

Template:Clade euphyllophyte

 
 
 
 
 

More recently, Gerrienne and Gonez have suggested a slightly different characterization of the early diverging polysporangiophytes:[21]

Polysporangiophytes
 

†'Protracheophytes'

 
 
 

†Paratracheophytes

 
 

Eutracheophytes

 
 
 

The paraphyletic protracheophytes, such as Aglaophyton, have water-conducting vessels like those of mosses, i.e., without cells containing thickened cell walls. The paratracheophytes, a name intended to replace Rhyniaceae or Rhyniopsida, have 'S-type' water-conducting cells, i.e., cells whose walls are thickened but in a much simpler fashion than those of true vascular plants, the eutracheophytes.[21]

進化[編輯]

Cooksonia pertoni的孢子體的復原圖，博伊斯認為其太小以不足以獨立生活。軸(莖)直徑約0.1毫米。

如果上面的發生樹是正確的If the cladogram above is correct it has implications for the evolution of land plants. The earliest diverging polysporangiophytes in the cladogram are the Horneophytopsida, a clade at the 'protracheophyte' grade that is sister to all other polysporangiophytes. They had essentially an isomorphic alternation of generations (meaning that the sporophytes and gametophytes were equally free living), which might suggest that both the gametophyte-dominant life style of bryophytes and the sporophyte-dominant life style of vascular plants evolved from this isomorphic condition. They were leafless and did not have true vascular tissues. In particular, they did not have tracheids: elongated cells that help transport water and mineral salts, and that develop a thick lignified wall at maturity that provides mechanical strength. Unlike plants at the bryophyte grade, their sporophytes were branched.[22]

According to the cladogram, the genus Rhynia illustrates two steps in the evolution of modern vascular plants. Plants have vascular tissue, albeit significantly simpler than modern vascular plants. Their gametophytes are distinctly smaller than their sporophytes (but have vascular tissue, unlike almost all modern vascular plants).[23]

The remainder of the polysporangiophytes divide into two lineages, a deep phylogenetic split that occurred in the early to mid Devonian, around 400 million years ago. Both lineages have developed leaves, but of different kinds. The lycophytes, which make up less than 1% of the species of living vascular plants, have small leaves (microphylls or more specifically lycophylls), which develop from an intercalary meristem (i.e., the leaves effectively grow from the base). The euphyllophytes are by far the largest group of vascular plants, in terms of both individuals and species. Euphyllophytes have large 'true' leaves (megaphylls), which develop through marginal or apical meristems (i.e., the leaves effectively grow from the sides or the apex).[24]

Both the cladogram derived from Kenrick and Crane's studies and its implications for the evolution of land plants have been questioned by others. A 2008 review by Gensel notes that recently discovered fossil spores suggest that tracheophytes were present earlier than previously thought; perhaps earlier than supposed stem group members. Spore diversity suggests that there were many plant groups, of which no other remains are known. Some early plants may have had heteromorphic alternation of generations, with later acquisition of isomorphic gametophytes in certain lineages.[25]

上面的演化樹顯示「protracheophytes」的分化比lycophytes早；然而， lycophytes were present in the Ludfordian stage of the Silurian around Template:Period span/brief, long before the 'protracheophytes' found in the Rhynie chert, dated to the Pragian stage of the Devonian around Template:Period span/brief.[26] However, it has been suggested that the poorly preserved Eohostimella, found in deposits of Early Silurian age (Llandovery, around Template:Period span/brief), may be a rhyniophyte.[27]

博伊斯表示一些Cooksonia同屬的孢子體的軸太窄，無法支持足夠的光合作用，使它們獨立於配子體發育，這與它們在演化樹中的地位不符。[28]

植物的進化史還遠未解決。

參見：Evolutionary history of plants和List of Early Devonian land plants

註釋和引用[編輯]

  1. ^ See, e.g., Edwards, D. & Wellman, C. (2001), "Embryophytes on Land: The Ordovician to Lochkovian (Lower Devonian) Record" in Gensel & Edwards 2001，第3–28頁
  2. ^ 2.0 2.1 Taylor, T.N.; Taylor, E.L. & Krings, M., Paleobotany, The Biology and Evolution of Fossil Plants 2nd, Amsterdam; Boston: Academic Press, 2009, ISBN 978-0-12-373972-8 , p. 225ff
  3. ^ Gensel, P.G. & Edwards, D. (編), Plants invade the Land : Evolutionary & Environmental Perspectives, New York: Columbia University Press, 2001, ISBN 978-0-231-11161-4 , chapters 2, 6, 7
  4. ^ 4.0 4.1 Kenrick & Crane 1997a，第139–140, 249頁
  5. ^ 5.0 5.1 Crane, P.R.; Herendeen, P. & Friis, E.M., Fossils and plant phylogeny, American Journal of Botany, 2004, 91 (10): 1683–99, PMID 21652317, doi:10.3732/ajb.91.10.1683 
  6. ^ Taylor, Taylor & Krings 2009，第226頁.
  7. ^ Banks, H.P., The early history of land plants, Drake, E.T. (編), Evolution and Environment: A Symposium Presented on the Occasion of the 100th Anniversary of the Foundation of Peabody Museum of Natural History at Yale University, New Haven, Conn.: Yale University Press: 73–107, 1968 , cited in Banks 1980
  8. ^ Banks, H.P., Reclassification of Psilophyta, Taxon, 1975, 24 (4): 401–413, doi:10.2307/1219491 
  9. ^ 9.0 9.1 9.2 Taylor, Taylor & Krings 2009，第227頁
  10. ^ See, e.g., Berry, C.M. & Fairon-Demaret, M. (2001), "The Middle Devonian Flora Revisited", in Gensel & Edwards 2001，第120–139頁
  11. ^ Banks, H.P., Evolution and Plants of the Past, London: Macmillan Press, 1970, ISBN 978-0-333-14634-7 , p. 57
  12. ^ Although this name has appeared in some sources, e.g., Knoll, Andrew H., Review of The Origin and Early Diversification of Land Plants: A Cladistic Study by Paul Kenrick; Peter Crane, International Journal of Plant Sciences, 1998-01-01, 159 (1): 172–174, JSTOR 2474949, doi:10.1086/297535 , it appears to be a mistake, as it is not in accord with Article 16 of the International Code of Botanical Nomenclature.
  13. ^ The name is based on the genus Trimerophyton; Article 16.4 of the International Code of Botanical Nomenclature allows the phyton part to be omitted before -ophyta, -ophytina, and -opsida.
  14. ^ Banks, H.P., The role of Psilophyton in the evolution of vascular plants, Review of Palaeobotany and Palynology, 1980, 29: 165–176, doi:10.1016/0034-6667(80)90056-1 
  15. ^ Kenrick, Paul & Crane, Peter R., The Origin and Early Diversification of Land Plants: A Cladistic Study, Washington, D.C.: Smithsonian Institution Press, 1997a, ISBN 978-1-56098-730-7 
  16. ^ Kenrick, P. & Crane, P.R., The origin and early evolution of plants on land, Nature, 1997b, 389 (6646): 33–39, Bibcode:1997Natur.389...33K, doi:10.1038/37918 
  17. ^ Berry & Fairon-Demaret 2001，第127頁
  18. ^ Cantino, Philip D.; James A. Doyle; Sean W. Graham; Walter S. Judd; Richard G. Olmstead; Douglas E. Soltis; Pamela S. Soltis; Michael J. Donoghue, Towards a Phylogenetic Nomenclature of Tracheophyta, Taxon, 2007, 56 (3): 822–846, doi:10.2307/25065865 
  19. ^ Taylor, D.W.; Li, Hongqi; Dahl, Jeremy; Fago, F.J.; Zinneker, D.; Moldowan, J.M., Biogeochemical evidence for the presence of the angiosperm molecular fossil oleanane in Paleozoic and Mesozoic non-angiospermous fossils, Paleobiology, 2006, 32 (2): 179–90, ISSN 0094-8373, doi:10.1666/0094-8373(2006)32[179:BEFTPO]2.0.CO;2 
  20. ^ Rothwell, G.W. & Nixon, K.C., How Does the Inclusion of Fossil Data Change Our Conclusions about the Phylogenetic History of Euphyllophytes?, International Journal of Plant Sciences, 2006, 167 (3): 737–749, doi:10.1086/503298 
  21. ^ 21.0 21.1 Gerrienne, P. & Gonez, P., Early evolution of life cycles in embryophytes: A focus on the fossil evidence of gametophyte/sporophyte size and morphological complexity, Journal of Systematics and Evolution, 2011, 49: 1–16, doi:10.1111/j.1759-6831.2010.00096.x 
  22. ^ Bateman, R.M.; Crane, P.R.; Dimichele, W.A.; Kenrick, P.R.; Rowe, N.P.; Speck, T.; Stein, W.E., Early Evolution of Land Plants: Phylogeny, Physiology, and Ecology of the Primary Terrestrial Radiation, Annual Review of Ecology and Systematics, 1998, 29 (1): 263–92, doi:10.1146/annurev.ecolsys.29.1.263 , p. 270
  23. ^ Kerp, H.; Trewin, N.H. & Hass, H., New gametophytes from the Early Devonian Rhynie chert, Transactions of the Royal Society of Edinburgh: Earth Sciences, 2004, 94: 411–28, doi:10.1017/s026359330000078x 
  24. ^ Pryer, K.M.; Schuettpelz, E.; Wolf, P.G.; Schneider, H.; Smith, A.R.; Cranfill, R., Phylogeny and evolution of ferns (monilophytes) with a focus on the early leptosporangiate divergences, American Journal of Botany, 2004, 91 (10): 1582–98 [2011-01-29], PMID 21652310, doi:10.3732/ajb.91.10.1582 , pp. 1582–3
  25. ^ Gensel, Patricia G., The Earliest Land Plants, Annu. Rev. Ecol. Evol. Syst., 2008, 39: 459–77, doi:10.1146/annurev.ecolsys.39.110707.173526 , pp. 470–2
  26. ^ Kotyk, M.E.; Basinger, J.F.; Gensel, P.G. & de Freitas, T.A., Morphologically complex plant macrofossils from the Late Silurian of Arctic Canada, Am. J. Bot., 2002, 89 (6): 1004–1013, PMID 21665700, doi:10.3732/ajb.89.6.1004 
  27. ^ Niklas, K.J., An Assessment of Chemical Features for the Classification of Plant Fossils, Taxon, 1979, 28 (5/6): 505, doi:10.2307/1219787 
  28. ^ Boyce, C.K., How green was Cooksonia? The importance of size in understanding the early evolution of physiology in the vascular plant lineage, Paleobiology, 2008, 34 (2): 179–194, ISSN 0094-8373, doi:10.1666/0094-8373(2008)034[0179:HGWCTI]2.0.CO;2 

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