Raffi at 04:56, 8 April 2007

2007-04-08T04:56:40Z

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{{Taxobox
| color = lightgreen
| name = Lycopodiophyta
| fossil_range = [[Silurian]] - Recent
| image = Lycopodium_plant.jpg
| image_width = 250px
| image_caption = ''Lycopodiella cernua''
| regnum = [[Plant]]ae
| divisio = '''Lycopodiophyta'''
| subdivision_ranks = [[Class (biology)|Classes]]
| subdivision =
[[Lycopodiopsida]] - clubmosses <br/>
[[Spikemoss|Selaginellopsida]] - spikemosses <br/>
[[Quillwort|Isoetopsida]] - quillworts
}}

The Division '''Lycopodiophyta''' (sometimes called '''Lycophyta''') is a [[vascular plant|tracheophyte]] subdivision of the Kingdom [[plant|Plantae]]. It is the oldest extant (living) vascular plant division at around 420 million years old, and includes some of the most "primitive" extant species. These species reproduce by shedding [[spore]]s and have macroscopic [[alternation of generations]], although some are [[homosporous]] while others are [[heterosporous]]. They differ from all other vascular plants in having [[microphyll]]s, leaves that have only a single vascular trace (vein) rather than the much more complex megaphylls found in [[fern]]s and [[seed plants]].

There are around 1,200 living species divided into three main groups within the Lycopodiophyta, sometimes separated at the level of order and sometimes at the level of class. These are subdivided at the class level here:

*Class [[Lycopodiopsida]] – clubmosses and firmosses
*Class [[Spikemoss|Selaginellopsida]] – spikemosses
*Class [[Quillwort|Isoetopsida]] – quillworts

The members of this division have a long evolutionary history, and [[fossil]]s are abundant worldwide, especially in coal [[deposits]]. In fact, most known [[Genus|genera]] are [[Extinction|extinct]]. The Silurian species ''[[Baragwanathia longifolia]]'' represents the earliest identifable Lycopodiophyta, while some ''[[Cooksonia]]'' seem to be related.

The Lycopodiophyta are one of several classes of plants that expanded onto land during the [[Silurian]] and [[Devonian]] periods. Like all explorers it found new hazards that demanded new solutions. While the ocean currents blended [[oxygen]], [[water]] and nutrients into a soup, the land had a layered structure with water and [[mineral]]s in the [[soil]] and oxygen and light in the air. The intense sunlight presented a greater risk of [[Genetics|genetic]] damage. Without water, pervasive desiccation became a possibility, and more structural support was required to resist [[gravity]].

[[Image:Lycopodiophyta_spores.jpg|Lycopodiophyta spores can be used in pyrotechnics|thumb|left]]

Many adaptations of the Lycopodiophyta can be explained as a response to these conditions. They continued the development and specialization of roots to extract [[nutrient]]s from the [[soil]] and developed leaves for [[photosynthesis]] and [[Cellular respiration|gas exchange]], using a stem for transport. A waxy cuticle helped retain moisture, and stoma allowed respiration. The vulnerable meiotic [[gametophyte]] is protected from [[radiation]] by its reduced size and often by the use of subterranean mycorhiza for its energy source instead of photosynthesis. Club-mosses are ''homosporous'', but spike-mosses and quillworts are ''heterosporous''. In heterospores the female spores are larger than the male because they store food for the new generation.

During the [[Carboniferous]] period, tree-like Lycopodiophyta (such as ''[[Lepidodendron]]'') formed huge forests and dominated the land. Unlike modern trees, leaves grew out of the entire surface of the trunk and branches, but would fall off as the plant grew, leaving only a small cluster of leaves at the top. Their remains formed many fossil [[coal]] deposits. In Fossil Park, [[Glasgow]], [[Scotland]], fossilized Lycopodiophyta trees can be found in [[sandstone]]. The trees are marked with diamond-shaped scars where they once had leaves.

The spores of Lycopodiophyta are highly flammable and so have been used in [[fireworks]]. Currently, [[huperzine]], a chemical isolated from a [[China|Chinese]] clubmoss, is under investigation as a possible treatmen
t for [[Alzheimer's disease]].

==External links==
{{Wikispecies|Lycopodiophyta}}
{{Wikibookspar|Dichotomous Key|Lycopodiophyta}}

*[http://www.ucmp.berkeley.edu/plants/lycophyta/lycophyta.html]
*[http://www.glasgowmuseums.com/venue/faq.cfm?venueid=2 Fossil Groves]
*[http://www.mdgekko.com/devonian/who/pages/lycopsid.html More About Lycopsids]
*[http://www.palaeos.com/Plants/Lycophytes/ Paleo Plants]
*[http://geowords.com/histbooknetscape/j11.htm The First Land Plants]

[[Category:Fossils]]
[[Category:Lycopodiophyta]]

Lycopodiophyta - Revision history

Raffi at 04:56, 8 April 2007