Editing Equisetum (section)

===Cell walls ===
The crude cell extracts of all ''Equisetum'' species tested contain [[mixed-linkage glucan : xyloglucan endotransglucosylase]] (MXE) activity.<ref>{{Cite journal | last1 = Fry | first1 = S. C. | last2 = Mohler | first2 = K. E. | last3 = Nesselrode | first3 = B. H. W. A. | last4 = Frankov | first4 = L. | title = Mixed-linkage -glucan:xyloglucan endotransglucosylase, a novel wall-remodelling enzyme from ''Equisetum'' (horsetails) and charophytic algae | doi = 10.1111/j.1365-313X.2008.03504.x | journal = The Plant Journal | volume = 55 | issue = 2 | pages = 240–252 | year = 2008 | pmid = 18397375| doi-access = free }}</ref> This is a novel enzyme and is not known to occur in any other plants. In addition, the cell walls of all ''Equisetum'' species tested contain [[mixed-linkage glucan]] (MLG), a [[polysaccharide]] which, until recently, was thought to be confined to the [[Poales]].<ref>{{cite journal|pmid=18393951 | doi=10.1111/j.1469-8137.2008.02435.x|title=Mixed-linkage (1→3,1→4)-β-d-glucan is a major hemicellulose of ''Equisetum'' (horsetail) cell walls|year=2008|last1=Fry|first1=Stephen C.|last2=Nesselrode|first2=Bertram H. W. A.|last3=Miller|first3=Janice G.|last4=Mewburn|first4=Ben R.|journal=New Phytologist|volume=179|pages=104–15|issue=1|doi-access=free| bibcode=2008NewPh.179..104F}}</ref><ref>{{cite journal|pmid=18284587 | doi=10.1111/j.1365-313X.2008.03453.x|title=Mixed-linkage (1→3),(1→4)-β-d-glucan is not unique to the Poales and is an abundant component of ''Equisetum arvense'' cell walls|year=2008|last1=Sørensen|first1=Iben|last2=Pettolino|first2=Filomena A.|last3=Wilson|first3=Sarah M.|last4=Doblin|first4=Monika S.|last5=Johansen|first5=Bo|last6=Bacic|first6=Antony|last7=Willats|first7=William G. T.|journal=The Plant Journal|volume=54|issue=3|pages=510–21|doi-access=free}}</ref> The evolutionary distance between ''Equisetum'' and the Poales suggests that each evolved MLG independently. The presence of MXE activity in ''Equisetum'' suggests that they have evolved MLG along with some mechanism of cell wall modification. Non-''Equisetum'' land plants tested lack detectable MXE activity. An observed negative correlation between [[Xyloglucan endotransglucosylase|XET]] activity and cell age led to the suggestion that XET is catalysing endotransglycosylation in controlled wall-loosening during cell expansion.<ref>{{cite journal|last1=Simmons|first1=Thomas J.|last2=Fry|first2=Stephen C. |url=http://www.biochemj.org/content/474/7/1055|title=Bonds broken & formed during the mixed-linkage glucan: xyloglucan endotransglucosylase reaction catalysed by Equisetum hetero-trans-β-glucanase|date=2017|journal= Biochemical Journal|doi=10.1042/BCJ20160935|pmc=5341106|pmid=28108640|volume=474|issue=7|pages=1055–1070|access-date=2019-07-17}}</ref> The lack of MXE in the Poales suggests that there it must play some other, currently unknown, role. Due to the correlation between MXE activity and cell age, MXE has been proposed to promote the cessation of cell expansion.{{citation needed|date=August 2016}}