Editing Plant cell (section)

=== Collenchyma ===
[[Ground tissue#Collenchyma|Collenchyma cells]] are alive at maturity and have thickened cellulose cell walls.<ref name="Cutter" /> These cells mature from meristem derivatives that initially resemble parenchyma, but differences quickly become apparent. Plastids do not develop, and the secretory apparatus (ER and Golgi) proliferates to secrete additional primary wall. The wall is most commonly thickest at the corners, where three or more cells come in contact, and thinnest where only two cells come in contact, though other arrangements of the wall thickening are possible.<ref name="Cutter" /> [[Pectin]] and [[hemicellulose]] are the dominant constituents of collenchyma cell walls of [[dicotyledon]] [[angiosperm]]s, which may contain as little as 20% of cellulose in ''[[Petasites]]''.<ref name="Roelofsen">{{cite book|last=Roelofsen|first=PA|title=The plant cell wall|date=1959|publisher=Gebrüder Borntraeger|location=Berlin|asin=B0007J57W0}}</ref> Collenchyma cells are typically quite elongated, and may divide transversely to give a septate appearance. The role of this cell type is to support the plant in axes still growing in length, and to confer flexibility and tensile strength on tissues. The primary wall lacks lignin that would make it tough and rigid, so this cell type provides what could be called plastic support – support that can hold a young stem or petiole into the air, but in cells that can be stretched as the cells around them elongate. Stretchable support (without elastic snap-back) is a good way to describe what collenchyma does. Parts of the strings in celery are collenchyma.

{{Plain image with caption|Plant cell types.svg|Cross section of a leaf showing various plant cell types|550px|right}}