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{{Taxobox
| color = lightgreen
| name = Land plants
| fossil_range = Latest [[Ordovician]] - Recent
| image = Fern.jpg
| image_width = 250px
| image_caption = Fern Leaf
| domain = [[Eukaryota]]
| unranked_regnum = [[Archaeplastida]]
| regnum = [[Plantae]]
| subregnum = '''Embryophyta'''
| subdivision_ranks = Divisions
| subdivision =
* '''[[Bryophyte|Non-vascular plants]] (bryophytes)'''
** [[Marchantiophyta]] - liverworts
** [[Hornwort|Anthocerotophyta]] - hornworts
** [[Moss|Bryophyta]] - mosses
* '''[[Vascular plant]]s (tracheophytes)'''
** [[Lycopodiophyta]] - clubmosses
** [[Equisetophyta]] - horsetails
** [[fern|Pteridophyta]] - "true" ferns
** [[whisk fern|Psilotophyta]] - whisk ferns
** [[Ophioglossophyta]] - adders'-tongues
** '''''[[Spermatophyta|Seed plants]] (spermatophytes)'''''
*** †[[Pteridospermatophyta]] - seed ferns
*** [[Pinophyta]] - conifers
*** [[Cycad|Cycadophyta]] - cycads
*** [[Ginkgo|Ginkgophyta]] - ginkgo
*** [[Gnetae|Gnetophyta]] - gnetae
*** [[Flowering plant|Magnoliophyta]] - flowering plants
}}
The '''embryophytes''' are the most familiar group of [[plant]]s. They include [[tree]]s, [[flower]]s, [[fern]]s, [[moss]]es, and various other '''green land plants'''. All are complex [[multicellular]] [[eukaryote]]s with specialized reproductive organs. With very few exceptions, embryophytes obtain their energy through [[photosynthesis]] (that is, by absorbing light); and they synthesize their food from [[carbon dioxide]]. '''Embryophyta''' may be distinguished from [[chlorophyll]]-using multicellular [[algae]] by having sterile tissue within the reproductive organs. Furthermore, embryophytes are primarily adapted for [[terrestrial|life on land]], although some are secondarily [[aquatic plant|aquatic]]. Accordingly, they are often called '''land plants'''.
Embryophytes developed from complex [[green alga]]e ([[Chlorophyta]]) during the [[Paleozoic]] era. The [[Charales]] or stoneworts appear to be the best living illustration of that developmental step. These alga-like plants undergo an [[alternation of generations|alternation]] between [[haploid]] and [[diploid]] generations (respectively called [[gametophyte]]s and [[sporophyte]]s). In the first embryophytes, however, the sporophytes became very different in structure and function, remaining small and dependent on the parent for their entire brief life. Such plants are informally called '[[bryophytes]]'. They include three surviving groups:
* [[moss|Bryophyta]] (mosses)
* [[hornwort|Anthocerotophyta]] (hornworts)
* [[Marchantiophyta]] (liverworts)
All of the above 'bryophytes' are relatively small and are usually confined to moist environments, relying on water to disperse their [[spore]]s. Other plants, better adapted to terrestrial conditions, appeared during the [[Silurian]] period. During the [[Devonian]] period, they diversified and spread to many different land environments, becoming the [[vascular plant]]s or [[Tracheophyta|tracheophytes]]. Tracheophyta have vascular tissues or [[tracheid]]s, which transport water throughout the body, and an outer layer or cuticle that resists [[desiccation|drying out]]. In most vascular plants, the sporophyte is the dominant individual, and develops true [[leaf|leaves]], [[Plant stem|stems]], and [[root]]s, while the gametophyte remains very small.
Many vascular plants, however, still reproduce using spores. They include the following extant groups:
* [[Lycopodiophyta]] ([[clubmoss]]es)
* [[Equisetophyta]] ([[horsetail]]s)
* [[whisk fern|Psilotophyta]] ([[whisk fern]]s)
* [[Ophioglossophyta]] ([[Ophioglossum|adders'-tongues]] and [[grape-fern]]s)
* [[Pteridophyta]] (ferns)
Other groups, which first appeared towards the end of the [[Paleozoic]] era, reproduce using [[desiccation]]-resistant capsules called [[seed]]s. These groups are accordingly called [[spermatophyte]]s or seed plants. In these forms, the gametophyte is completely reduced, taking the form of single-celled [[pollen]] and [[ovum|ova]], while the sporophyte begins its life enclosed within the seed. Some seed plants
may even survive in extremely arid conditions, unlike their more water-bound precursors. The seed plants include the following extant groups:
* [[Cycad]]ophyta (Cycads)
* [[Ginkgo]]phyta (Ginkgo)
* [[Pinophyta]] (Conifers)
* [[Gnetae|Gnetophyta]] (Gnetae)
* [[Flowering plant|Magnoliophyta]] (Flowering plants)
The first four groups are referred to as [[gymnosperm]]s, since the embryonic sporophyte is not enclosed until after pollination. In contrast, among the flowering plants or [[angiosperm]]s, the pollen has to grow a tube to penetrate the seed coat. Angiosperms were the last major group of plants to appear, developing from gymnosperms during the [[Jurassic]] period, and then spreading rapidly during the [[Cretaceous]]. They are the predominant group of plants in most [[terrestrial]] [[biome]]s today.
Note that the higher-level [[Statistical classification|classification]] of plants varies considerably. Some authors have restricted the [[kingdom]] [[Plantae]] to include only embryophytes, others have given them various names and ranks. The groups listed here are often considered divisions or [[phylum|phyla]], but have also been treated as classes, and they are occasionally compressed into as few as two divisions. Some classifications, indeed, consider the term Embryophyta at the superphylum (superdivision) level, and include Land Plants and some Charophyceae in a subkingdom named [[Streptophyta]].
On a microscopic level, embryophyte cells remain very similar to those of green algae. They are [[eukaryote|eukaryotic]], with a [[cell wall]] composed of [[cellulose]] and [[plastid]]s surrounded by two membranes. These usually take the form of [[chloroplast]]s, which conduct photosynthesis and store food in the form of [[starch]], and characteristically are pigmented with [[chlorophyll]]s ''a'' and ''b'', generally giving them a bright green color. Embryophytes also generally have an enlarged central [[vacuole]] or tonoplast, which maintains cell [[turgor]] and keeps the plant rigid. They lack [[flagellum|flagella]] and [[centriole]]s except in certain [[gamete]]s.
== References ==
* Kenrick, Paul & Crane, Peter R. (1997). ''The Origin and Early Diversification of Land Plants: A Cladistic Study''. Washington, D. C.: Smithsonian Institution Press. ISBN 1-56098-730-8.
* Raven, Peter H., Evert, Ray F., & Eichhorn, Susan E. (2005). ''Biology of Plants'' (7th ed.). New York: W. H. Freeman and Company. ISBN 0-7167-1007-2.
* Stewart, Wilson N. & Rothwell, Gar W. (1993). ''Paleobotany and the Evolution of Plants'' (2nd ed.). Cambridge: [[Cambridge University Press]]. ISBN 0-521-38294-7.
* Taylor, Thomas N. & Taylor, Edith L. (1993). ''The Biology and Evolution of Fossil Plants''. Englewood Cliffs, NJ: Prentice Hall. ISBN 0-13-651589-4.
[[Category:Plants]]
[[Category:Plant taxonomy]]
| color = lightgreen
| name = Land plants
| fossil_range = Latest [[Ordovician]] - Recent
| image = Fern.jpg
| image_width = 250px
| image_caption = Fern Leaf
| domain = [[Eukaryota]]
| unranked_regnum = [[Archaeplastida]]
| regnum = [[Plantae]]
| subregnum = '''Embryophyta'''
| subdivision_ranks = Divisions
| subdivision =
* '''[[Bryophyte|Non-vascular plants]] (bryophytes)'''
** [[Marchantiophyta]] - liverworts
** [[Hornwort|Anthocerotophyta]] - hornworts
** [[Moss|Bryophyta]] - mosses
* '''[[Vascular plant]]s (tracheophytes)'''
** [[Lycopodiophyta]] - clubmosses
** [[Equisetophyta]] - horsetails
** [[fern|Pteridophyta]] - "true" ferns
** [[whisk fern|Psilotophyta]] - whisk ferns
** [[Ophioglossophyta]] - adders'-tongues
** '''''[[Spermatophyta|Seed plants]] (spermatophytes)'''''
*** †[[Pteridospermatophyta]] - seed ferns
*** [[Pinophyta]] - conifers
*** [[Cycad|Cycadophyta]] - cycads
*** [[Ginkgo|Ginkgophyta]] - ginkgo
*** [[Gnetae|Gnetophyta]] - gnetae
*** [[Flowering plant|Magnoliophyta]] - flowering plants
}}
The '''embryophytes''' are the most familiar group of [[plant]]s. They include [[tree]]s, [[flower]]s, [[fern]]s, [[moss]]es, and various other '''green land plants'''. All are complex [[multicellular]] [[eukaryote]]s with specialized reproductive organs. With very few exceptions, embryophytes obtain their energy through [[photosynthesis]] (that is, by absorbing light); and they synthesize their food from [[carbon dioxide]]. '''Embryophyta''' may be distinguished from [[chlorophyll]]-using multicellular [[algae]] by having sterile tissue within the reproductive organs. Furthermore, embryophytes are primarily adapted for [[terrestrial|life on land]], although some are secondarily [[aquatic plant|aquatic]]. Accordingly, they are often called '''land plants'''.
Embryophytes developed from complex [[green alga]]e ([[Chlorophyta]]) during the [[Paleozoic]] era. The [[Charales]] or stoneworts appear to be the best living illustration of that developmental step. These alga-like plants undergo an [[alternation of generations|alternation]] between [[haploid]] and [[diploid]] generations (respectively called [[gametophyte]]s and [[sporophyte]]s). In the first embryophytes, however, the sporophytes became very different in structure and function, remaining small and dependent on the parent for their entire brief life. Such plants are informally called '[[bryophytes]]'. They include three surviving groups:
* [[moss|Bryophyta]] (mosses)
* [[hornwort|Anthocerotophyta]] (hornworts)
* [[Marchantiophyta]] (liverworts)
All of the above 'bryophytes' are relatively small and are usually confined to moist environments, relying on water to disperse their [[spore]]s. Other plants, better adapted to terrestrial conditions, appeared during the [[Silurian]] period. During the [[Devonian]] period, they diversified and spread to many different land environments, becoming the [[vascular plant]]s or [[Tracheophyta|tracheophytes]]. Tracheophyta have vascular tissues or [[tracheid]]s, which transport water throughout the body, and an outer layer or cuticle that resists [[desiccation|drying out]]. In most vascular plants, the sporophyte is the dominant individual, and develops true [[leaf|leaves]], [[Plant stem|stems]], and [[root]]s, while the gametophyte remains very small.
Many vascular plants, however, still reproduce using spores. They include the following extant groups:
* [[Lycopodiophyta]] ([[clubmoss]]es)
* [[Equisetophyta]] ([[horsetail]]s)
* [[whisk fern|Psilotophyta]] ([[whisk fern]]s)
* [[Ophioglossophyta]] ([[Ophioglossum|adders'-tongues]] and [[grape-fern]]s)
* [[Pteridophyta]] (ferns)
Other groups, which first appeared towards the end of the [[Paleozoic]] era, reproduce using [[desiccation]]-resistant capsules called [[seed]]s. These groups are accordingly called [[spermatophyte]]s or seed plants. In these forms, the gametophyte is completely reduced, taking the form of single-celled [[pollen]] and [[ovum|ova]], while the sporophyte begins its life enclosed within the seed. Some seed plants
may even survive in extremely arid conditions, unlike their more water-bound precursors. The seed plants include the following extant groups:
* [[Cycad]]ophyta (Cycads)
* [[Ginkgo]]phyta (Ginkgo)
* [[Pinophyta]] (Conifers)
* [[Gnetae|Gnetophyta]] (Gnetae)
* [[Flowering plant|Magnoliophyta]] (Flowering plants)
The first four groups are referred to as [[gymnosperm]]s, since the embryonic sporophyte is not enclosed until after pollination. In contrast, among the flowering plants or [[angiosperm]]s, the pollen has to grow a tube to penetrate the seed coat. Angiosperms were the last major group of plants to appear, developing from gymnosperms during the [[Jurassic]] period, and then spreading rapidly during the [[Cretaceous]]. They are the predominant group of plants in most [[terrestrial]] [[biome]]s today.
Note that the higher-level [[Statistical classification|classification]] of plants varies considerably. Some authors have restricted the [[kingdom]] [[Plantae]] to include only embryophytes, others have given them various names and ranks. The groups listed here are often considered divisions or [[phylum|phyla]], but have also been treated as classes, and they are occasionally compressed into as few as two divisions. Some classifications, indeed, consider the term Embryophyta at the superphylum (superdivision) level, and include Land Plants and some Charophyceae in a subkingdom named [[Streptophyta]].
On a microscopic level, embryophyte cells remain very similar to those of green algae. They are [[eukaryote|eukaryotic]], with a [[cell wall]] composed of [[cellulose]] and [[plastid]]s surrounded by two membranes. These usually take the form of [[chloroplast]]s, which conduct photosynthesis and store food in the form of [[starch]], and characteristically are pigmented with [[chlorophyll]]s ''a'' and ''b'', generally giving them a bright green color. Embryophytes also generally have an enlarged central [[vacuole]] or tonoplast, which maintains cell [[turgor]] and keeps the plant rigid. They lack [[flagellum|flagella]] and [[centriole]]s except in certain [[gamete]]s.
== References ==
* Kenrick, Paul & Crane, Peter R. (1997). ''The Origin and Early Diversification of Land Plants: A Cladistic Study''. Washington, D. C.: Smithsonian Institution Press. ISBN 1-56098-730-8.
* Raven, Peter H., Evert, Ray F., & Eichhorn, Susan E. (2005). ''Biology of Plants'' (7th ed.). New York: W. H. Freeman and Company. ISBN 0-7167-1007-2.
* Stewart, Wilson N. & Rothwell, Gar W. (1993). ''Paleobotany and the Evolution of Plants'' (2nd ed.). Cambridge: [[Cambridge University Press]]. ISBN 0-521-38294-7.
* Taylor, Thomas N. & Taylor, Edith L. (1993). ''The Biology and Evolution of Fossil Plants''. Englewood Cliffs, NJ: Prentice Hall. ISBN 0-13-651589-4.
[[Category:Plants]]
[[Category:Plant taxonomy]]