Vernation (from vernal meaning spring, since that is when leaves spring forth in temperate regions) is the formation of new leaves or fronds. In plant anatomy, it is the arrangement of leaves in a bud.
In pine species, new leaves are short and encased in sheaths. Each leaf bundle consists of 2 to 5 needles. All the leaves on one section of branch grow in length together. In cabbage species, new leaves are folded over, each covered by the previous leaf.
This fern is producing a new frond by the process of 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 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 leaflets, in the compound leaves of cycads.[1] Circinate vernation is also typical of the carnivorous plant family Droseraceae,[2] for example see this photo of Drosera filiformis. It is also seen in the related genera Drosophyllum and Triphyophyllum, and in the much more distantly related 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.[3]
Convolute vernation
This hosta leaf is produced by convolute vernation.
The process of convolute vernation involves the wrapping of one margin of the leaf's blade over the other. This folding mechanism makes the emerging leaf look like a tube.
Involute vernation
These cycad leaves are produced by involute vernation.
In involute vernation both margins on opposing sides of the leaf are rolled up towards the upper (axial) surface of the leaf, forming two tubes that may meet at the midrib of the leaf.
Revolute vernation
Revolute vernation is the opposite of involute vernation: the margins of the leaf are rolled up towards the under (abaxial) surface of the leaf.[4]
^Cameron, K. M.; Wurdack, K. J.; Jobson, R. W. (2002), "Molecular evidence for the common origin of snap-traps among carnivorous plants", American Journal of Botany, 89 (9): 1503–1509, doi:10.3732/ajb.89.9.1503, PMID 21665752
^Ellison, Aaron M.; Adamec, Lubomír (2018). Carnivorous plants: physiology, ecology, and evolution. Oxford, UK: Oxford University Press. p. 30. ISBN978-0198779841.
Wikisource has the text of The New Student's Reference Work article "Vernation".
January 30, 2023
vernation, confused, with, venation, from, vernal, meaning, spring, since, that, when, leaves, spring, forth, temperate, regions, formation, leaves, fronds, plant, anatomy, arrangement, leaves, pine, species, leaves, short, encased, sheaths, each, leaf, bundle. Not to be confused with Venation Vernation from vernal meaning spring since that is when leaves spring forth in temperate regions is the formation of new leaves or fronds In plant anatomy it is the arrangement of leaves in a bud In pine species new leaves are short and encased in sheaths Each leaf bundle consists of 2 to 5 needles All the leaves on one section of branch grow in length together In cabbage species new leaves are folded over each covered by the previous leaf Contents 1 Circinate vernation 2 Convolute vernation 3 Involute vernation 4 Revolute vernation 5 See also 6 ReferencesCircinate vernation Edit This fern is producing a new frond by the process of 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 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 leaflets in the compound leaves of cycads 1 Circinate vernation is also typical of the carnivorous plant family Droseraceae 2 for example see this photo of Drosera filiformis It is also seen in the related genera Drosophyllum and Triphyophyllum and in the much more distantly related 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 3 Convolute vernation Edit This hosta leaf is produced by convolute vernation The process of convolute vernation involves the wrapping of one margin of the leaf s blade over the other This folding mechanism makes the emerging leaf look like a tube Involute vernation Edit These cycad leaves are produced by involute vernation In involute vernation both margins on opposing sides of the leaf are rolled up towards the upper axial surface of the leaf forming two tubes that may meet at the midrib of the leaf Revolute vernation EditRevolute vernation is the opposite of involute vernation the margins of the leaf are rolled up towards the under abaxial surface of the leaf 4 See also EditAestivation the way in which the petals and sepals of a flower are arranged in a bud Ptyxis the way an individual leaf is folded within a bud References Edit Circinate vernation Cameron K M Wurdack K J Jobson R W 2002 Molecular evidence for the common origin of snap traps among carnivorous plants American Journal of Botany 89 9 1503 1509 doi 10 3732 ajb 89 9 1503 PMID 21665752 Ellison Aaron M Adamec Lubomir 2018 Carnivorous plants physiology ecology and evolution Oxford UK Oxford University Press p 30 ISBN 978 0198779841 Beentje Henk 2010 The Kew Plant Glossary Richmond Surrey Royal Botanic Gardens Kew p 101 ISBN 978 1 84246 422 9 Wikisource has the text of The New Student s Reference Work article Vernation Retrieved from https en wikipedia org w index php title Vernation amp oldid 1111560605, wikipedia, wiki, book, books, library,
