Editing Embryophyte (section)

==Description==
[[File:Garden Primeval - US Botanic Gardens 37.jpg|thumb |[[Moss]], [[Lycopodiaceae|clubmoss]], [[fern]]s and [[cycad]]s in a greenhouse]]
The Embryophytes emerged either a half-billion years ago, at some time in the interval between the mid-[[Cambrian]] and early [[Ordovician]], or almost a billion years ago, during the Tonian or Cryogenian,<ref>{{Cite journal |last1=Su |first1=Danyan |last2=Yang |first2=Lingxiao |last3=Shi |first3=Xuan |last4=Ma |first4=Xiaoya |last5=Zhou |first5=Xiaofan |last6=Hedges |first6=S Blair |last7=Zhong |first7=Bojian |date=2021-07-29 |editor-last=Battistuzzi |editor-first=Fabia Ursula |title=Large-Scale Phylogenomic Analyses Reveal the Monophyly of Bryophytes and Neoproterozoic Origin of Land Plants |url=https://academic.oup.com/mbe/article/38/8/3332/6237914 |journal=Molecular Biology and Evolution |language=en |volume=38 |issue=8 |pages=3332–3344 |doi=10.1093/molbev/msab106 |issn=1537-1719 |pmc=8321542 |pmid=33871608}}</ref> probably from freshwater [[charophyte]]s, a clade of multicellular [[green algae]] similar to extant [[Klebsormidiophyceae]].<ref>{{cite journal |last1=Frangedakis |first1=Eftychios |last2=Shimamura |first2=Masaki |last3=Villarreal |first3=Juan Carlos |last4=Li |first4=Fay-Wei |last5=Tomaselli |first5=Marta |last6=Waller |first6=Manuel |last7=Sakakibara |first7=Keiko |last8=Renzaglia |first8=Karen S. |last9=Szövényi |first9=Péter |title=The hornworts: morphology, evolution and development |journal=New Phytologist |date=January 2021 |volume=229 |issue=2 |pages=735–754 |doi=10.1111/nph.16874 |pmid=32790880 |pmc=7881058 }}</ref><ref name="Niklas-2010">{{Citation |last1=Niklas |first1=K.J. |last2=Kutschera |first2=U. |year=2010 |title=The evolution of the land plant life cycle |journal=New Phytologist |volume=185 |issue=1 |pages=27–41 |doi=10.1111/j.1469-8137.2009.03054.x |pmid=19863728 |postscript=. |doi-access=free }}</ref><ref>{{cite journal |last1=de Vries |first1=J |last2=Archibald |first2=JM |title=Plant evolution: landmarks on the path to terrestrial life. |journal=The New Phytologist |date=March 2018 |volume=217 |issue=4 |pages=1428–1434 |doi=10.1111/nph.14975 |pmid=29318635 |doi-access=free}}</ref><ref>{{Cite journal |last=Del-Bem |first=Luiz-Eduardo |date=2018-05-31 |title=Xyloglucan evolution and the terrestrialization of green plants |journal=New Phytologist |language=en |volume=219 |issue=4 |pages=1150–1153 |doi=10.1111/nph.15191 |pmid=29851097 |issn=0028-646X |doi-access=free|hdl=1843/36860 |hdl-access=free }}</ref> The emergence of the Embryophytes depleted atmospheric CO<sub>2</sub> (a [[greenhouse gas]]), leading to [[Ice age|global cooling]], and thereby precipitating [[glaciation]]s.<ref>{{cite journal |last1=Donoghue |first1=Philip C.J. |last2=Harrison |first2=C. Jill |last3=Paps |first3=Jordi |last4=Schneider |first4=Harald |title=The evolutionary emergence of land plants |journal=Current Biology |date=October 2021 |volume=31 |issue=19 |pages=R1281–R1298 |doi=10.1016/j.cub.2021.07.038 |pmid=34637740 |bibcode=2021CBio...31R1281D |s2cid=238588736 |hdl=1983/662d176e-fcf4-40bf-aa8c-5694a86bd41d |hdl-access=free }}</ref> Embryophytes are primarily adapted for life on land, although some are secondarily [[aquatic plant|aquatic]]. Accordingly, they are often called land plants or terrestrial plants.{{cn|date=April 2025}}

On a microscopic level, the cells of charophytes are broadly similar to those of [[chlorophyte]] green algae, but differ in that in cell division the daughter nuclei are separated by a [[phragmoplast]].<ref name="Pickett-Heaps-1976">{{cite journal | last1 = Pickett-Heaps | first1 = J. | year = 1976 | title = Cell division in eucaryotic algae | journal = BioScience | volume = 26 | issue = 7 | pages = 445–450 | doi=10.2307/1297481 | jstor = 1297481 }}</ref> They are [[eukaryote|eukaryotic]], with a [[cell wall]] composed of [[cellulose]] and [[plastid]]s surrounded by two membranes. The latter include [[chloroplast]]s, which conduct photosynthesis and store food in the form of [[starch]], and are characteristically pigmented with chlorophylls ''a'' and ''b'', generally giving them a bright green color. Embryophyte cells also generally have an enlarged central [[vacuole]] enclosed by a vacuolar membrane or tonoplast, which maintains cell [[turgor]] and keeps the plant rigid.{{cn|date=April 2025}}

In common with all groups of multicellular algae they have a life cycle which involves [[alternation of generations]]. A multicellular [[haploid]] generation with a single set of [[chromosome]]s – the [[gametophyte]] – produces sperm and eggs which fuse and grow into a [[diploid]] multicellular generation with twice the number of chromosomes – the [[sporophyte]] which produces haploid [[spore]]s at maturity. The spores divide repeatedly by [[mitosis]] and grow into a gametophyte, thus completing the cycle. Embryophytes have two features related to their reproductive cycles which distinguish them from all other plant lineages. Firstly, their gametophytes produce sperm and eggs in multicellular structures (called '[[antheridium|antheridia]]' and '[[archegonium|archegonia]]'), and fertilization of the ovum takes place within the archegonium rather than in the external environment. Secondly, the initial stage of development of the fertilized egg (the [[zygote]]) into a diploid multicellular sporophyte, takes place within the archegonium where it is both protected and provided with nutrition. This second feature is the origin of the term 'embryophyte' – the fertilized egg develops into a protected embryo, rather than dispersing as a single cell.<ref name="Niklas-2010"/> In the [[bryophyte]]s the sporophyte remains dependent on the gametophyte, while in all other embryophytes the sporophyte generation is dominant and capable of independent existence.{{cn|date=April 2025}}

Embryophytes also differ from algae by having [[Metamerism (biology)|metamers]]. Metamers are repeated units of development, in which each unit derives from a single cell, but the resulting product tissue or part is largely the same for each cell. The whole organism is thus constructed from similar, repeating parts or ''metamers''. Accordingly, these plants are sometimes termed 'metaphytes' and classified as the group Metaphyta<ref>{{citation |last=Mayr |first=E. |year=1990 |title=A natural system of organisms |journal=Nature |volume=348 |page=491 |bibcode= 1990Natur.348..491M |doi= 10.1038/348491a0 |issue=6301 |s2cid=13454722 |doi-access=free }}</ref> (but [[Haeckel]]'s definition of Metaphyta places some algae in this group<ref>{{cite web |url=https://archive.org/details/systematischephy01haec |title=Systematische phylogenie |first=Ernst Heinrich Philipp August |last=Haeckel |date=28 September 1894 |publisher=Berlin : Georg Reimer |via=Internet Archive}}</ref>). In all land plants a disc-like structure called a [[phragmoplast]] forms where the cell will [[Cytokinesis#Plant Cell Cytokinesis|divide]], a trait only found in the land plants in the [[Streptophytina|streptophyte]] lineage, some species within their relatives [[Coleochaetales]], [[Charales]] and [[Zygnematales]], as well as within [[subaerial]] species of the algae order [[Trentepohliales]], and appears to be essential in the adaptation towards a terrestrial life style.<ref>{{cite journal |url=http://www.nature.com/news/2001/010219/full/conference010222-8.html |title=Land plants divided and ruled |first=Whitfield |last=John |date=19 February 2001 |journal=Nature News |pages=conference010222–8 |doi=10.1038/conference010222-8|url-access=subscription }}</ref><ref>{{Cite journal |last=López-Bautista |first=Juan M. |last2=Waters |first2=Debra A. |last3=Chapman |first3=Russell L. |date=2003 |title=Phragmoplastin, green algae and the evolution of cytokinesis |url=https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.02561-0 |journal=International Journal of Systematic and Evolutionary Microbiology |volume=53 |issue=6 |pages=1715–1718 |doi=10.1099/ijs.0.02561-0 |issn=1466-5034}}</ref><ref>{{cite web |url=http://news.sciencemag.org/sciencenow/2001/02/19-04.html |title=Invasions of the Algae - ScienceNOW - News - Science |access-date=2013-03-27 |archive-url=https://web.archive.org/web/20130602060506/http://news.sciencemag.org/sciencenow/2001/02/19-04.html |archive-date=2013-06-02 |url-status=dead}}</ref><ref>{{Cite web |url=http://news.nationalgeographic.com/news/2001/06/0604_wirealgae.html |archive-url=https://web.archive.org/web/20020126211113/http://news.nationalgeographic.com/news/2001/06/0604_wirealgae.html |url-status=dead |archive-date=January 26, 2002 |title=All Land Plants Evolved From Single Type of Algae, Scientists Say}}</ref>