Editing Vernation (section)

==Circinate vernation==

{{anchor|circinate}}
[[File:Circinate_vernation.jpg|thumb|upright|This fern is producing a new frond by circinate vernation.]]

'''Circinate vernation''' is the manner in which most [[fern]] fronds emerge.  As the fern frond is formed, it is  tightly curled so that the tender growing tip of the frond (and each subdivision of the frond) is protected within a coil. At this stage it is called a [[crozier]] (after the [[shepherd]]'s crook) or [[fiddlehead]] (after the [[scrollwork]] at the top of a violin). As the lower parts of the frond expand and toughen up, they begin to [[Photosynthesis|photosynthesize]], supporting the further growth and expansion of the frond. By photosynthesizing, the frond increases the amount of solute inside the frond, which lowers the internal water gradient and facilitates an increase in volume that forces uncoiling. In the case of many fronds, long hairs or scales provide additional protection to the growing tips before they are fully uncoiled. Circinate vernation may also be observed in the extension of [[leaflet (botany)|leaflets]], in the [[compound leaves]] of [[cycads]].<ref>{{Cite web |url=http://ponnvandu.wordpress.com/category/circinate-vernation/ |title=Circinate vernation}}</ref> Circinate vernation is also typical of the carnivorous plant family [[Droseraceae]],<ref name="cameron">{{citation |doi=10.3732/ajb.89.9.1503 |title=Molecular evidence for the common origin of snap-traps among carnivorous plants |year=2002 |author=Cameron, K. M. |journal=American Journal of Botany |volume=89 |issue=9 |pages=1503–1509 |last2=Wurdack |first2=K. J. |last3=Jobson |first3=R. W. |pmid=21665752}}</ref> for example see [[:File:Drosera filiformis ne1.jpg|this photo]] of  ''[[Drosera filiformis]]''. It is also seen in the related genera ''[[Drosophyllum]]'' and ''[[Triphyophyllum]]'', and in the much more distantly related ''[[Byblis (plant)|Byblis]]''; however in these three genera, the leaves are coiled ''outwards'' towards the abaxial surface of the leaf (reverse circinate vernation): this appears to be unique to these three plants among the angiosperms.<ref>{{cite book |last1=Ellison |first1=Aaron M. |last2=Adamec |first2=Lubomír |title=Carnivorous plants: physiology, ecology, and evolution |date=2018 |publisher=Oxford University Press |location=Oxford, UK |isbn=978-0198779841 |page=30}}</ref> {{clear}}