Vernation or leafing is the formation of new

leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...

frond A frond is a large, divided leaf. In both common usage and botanical nomenclature, the leaves of ferns are referred to as fronds and some botanists restrict the term to this group. Other botanists allow the term frond to also apply to the lar ...

s. In plant anatomy, it is the arrangement of leaves in a

bud In botany, a bud is an undeveloped or Plant embryogenesis, embryonic Shoot (botany), shoot and normally occurs in the axil of a leaf or at the tip of a Plant stem, stem. Once formed, a bud may remain for some time in a dormancy, dormant conditi ...

. In

pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. ''World Flora Online'' accepts 134 species-rank taxa (119 species and 15 nothospecies) of pines as cu ...

species, new leaves are short and encased in sheaths. Each leaf bundle consists of two to five needles. All the leaves on one section of branch grow in length together. In

cabbage Cabbage, comprising several cultivars of '' Brassica oleracea'', is a leafy green, red (purple), or white (pale green) biennial plant grown as an annual vegetable crop for its dense-leaved heads. It is descended from the wild cabbage ( ''B.& ...

species, new leaves are folded over, each covered by the previous leaf.

Name

The term ''vernation'' is borrowed from

New Latin Neo-LatinSidwell, Keith ''Classical Latin-Medieval Latin-Neo Latin'' in ; others, throughout. (also known as New Latin and Modern Latin) is the style of written Latin used in original literary, scholarly, and scientific works, first in Italy d ...

, the act of being verdant or flourishing (). It is

cognate In historical linguistics, cognates or lexical cognates are sets of words that have been inherited in direct descent from an etymological ancestor in a common parent language. Because language change can have radical effects on both the s ...

with (

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

for " spring") and ("vernal").

Circinate vernation

Circinate vernation is the manner in which most

fern The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...

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 A crozier or crosier (also known as a paterissa, pastoral staff, or bishop's staff) is a stylized staff that is a symbol of the governing office of a bishop or abbot and is carried by high-ranking prelates of Roman Catholic, Eastern Catholi ...

(after the

shepherd A shepherd is a person who tends, herds, feeds, or guards flocks of sheep. Shepherding is one of the world's oldest occupations; it exists in many parts of the globe, and it is an important part of Pastoralism, pastoralist animal husbandry. ...

's crook) or fiddlehead (after the

scrollwork The scroll in art is an element of ornament (art), ornament and graphic design featuring spirals and rolling incomplete circle motifs, some of which resemble the edge-on view of a book or document in scroll form, though many types are plant- ...

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. Circinate vernation is also typical of the carnivorous plant family

Droseraceae Droseraceae is a family of carnivorous flowering plants, also known as the sundew family. It consists of approximately 180 species in three extant genera, the vast majority being in the sundew genus '' Drosera''. The family also contains the wel ...

, for example see this photo of '' Drosera filiformis''. It is also seen in the related genera '' Drosophyllum'' and ''

Triphyophyllum ''Triphyophyllum peltatum'' is a facultatively carnivorous,Walker, C. (2023)Triggered by phosphorous 'sic''deficiency.Nature Plants, 9(6), 853-853. up to 60 m tall vineCross, A., Krueger, T., Restoration Ecology Lab, Ecological Health Network ...

'', 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.

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

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 A primary vein, also known as the midrib, is the main vascular structure running through the center of a leaf. The primary vein is crucial for the leaf’s efficiency in photosynthesis and overall health, as it ensures the proper flow of material ...

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.

References