Rocío de sol (Drosera rotundifolia)

Rocío de sol ( Drosera rotundifolia )
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Taxon biology
Drosera rotundifolia (the common sundew or round-leaved sundew) is a species of sundew, a
carnivorous plant often found in bogs, marshes and fens. One of the most widespread sundew species,
it is generally circumboreal, being found in all of northern Europe, much of Siberia, large parts of
northern North America, Korea, Japan and New Guinea.
The leaves of the common sundew are arranged in a basal rosette. The narrow, hairy, 1.3–5.0 cm long
petioles support 4–10 mm long laminae. The upper surface of the lamina is densely covered with red
glandular hairs that secrete a sticky mucilage.
A typical plant has a diameter of around 3-5 cm, with a 5–25 cm tall inflorescence. The flowers grow on
one side of a single slender, hairless stalk that emanates from the centre of the leaf rosette. White or
pink in colour, the five-petalled flowers produce 1.0–1.5 mm, light brown, slender, tapered seeds.[1]
In the winter, D. rotundifolia produces a hibernaculum to survive the cold conditions. This consists of a
bud of tightly curled leaves at ground level.
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The plant feeds on insects, which are attracted to its bright red colour and its glistening drops of
mucilage, loaded with a sugary substance, covering its leaves. It has evolved this carnivorous behaviour
in response to its habitat, which is usually poor in nutrients or is so acidic that nutrient availability is
severely decreased. The plant uses enzymes to dissolve the insects – which become stuck to the
glandular tentacles – and extracts ammonia (from proteins) and other nutrients from their bodies. The
ammonia replaces the nitrogen that other plants absorb from the soil.
Description
Le Rossolis à feuilles rondes ( Drosera rotundifolia L.) est une espèce de la famille des Droseraceae . Bien
que répartie sur l’ensemble du territoire français, sa présence n’est toujours que très locale et
dépendante des tourbières qui sont des milieux écologiques de plus en plus rares. Si cette espèce est
encore globalement bien représentée en zone de montagne, en plaine elle a considérablement
régressé, du fait de la destruction de ses habitats de prédilection.
Cette plante herbacée vivace n’excède que rarement 20 cm de hauteur. Ses feuilles sont disposées en
rosette, ont une forme arrondie et sont recouvertes de poils dont l’extrémité supérieure se transforme
en glande, produisant un suc collant, de 1 à 2 mm de diamètre. Les fleurs sont disposées en petites
grappes, parfois rameuses. Elles éclosent de mi-juin à fin-août, et sont de couleur blanche. Le périanthe
est constitué d’un calice pentamère dialysépale et d’une corolle actinomophe pentamère dialypétale et
marcescente. L’androcée est formé de 5 étamines. La pollinisation est essentiellement entomophile. Le
gynécée est tricarpellaire à pentacarpellaire, selon les individus, et gamocarpique. Le fruit est une
capsule.
Cette espèce possède des exigences écologiques très strictes. Elle ne pousse quand dans les zones de
tourbières : c’est-à-dire des marais tourbeux, acides et très peu minéralisés. La disparition de ces
habitats par enfrichement, leur destruction ou leur exploitation pour la récolte de la tourbe concourent
à la raréfaction du Rossolis à feuilles rondes.
Comme cette espèce pousse dans des milieux naturels pauvres en éléments nutritifs (en particulier les
molécules azotées), celle-ci les récupère directement sur des insectes qu’elle piège : le Rossolis à
feuilles rondes est une plante carnivore. Les poils glanduleux situés sur les feuilles collent et digèrent
des petites diptères et des fourmis, ce qui apporte à la plante les éléments qui lui sont nécessaires et
qui ne sont pas présents dans le substrat sur lequel elle pousse.
Le Rossolis à feuilles rondes possède des propriétés antitussives : il est encore largement utilisé dans
de nombreuses préparations pharmaceutiques. Il peut se confondre avec d’autres espèces du genre
Drosera , mais c’est le seul à présenter des feuilles arrondies, alors que les autres plantes proches
possèdent des feuilles plus ou moins allongées.
Référence bibliographique principale : COSTE H. – 1900-1906. Flore descriptive et illustrée de la France,
de la Corse et des contrées limitrophes . Tome I. Paul-Klincksieck, Paris. Réédition en 1998 par la
Librairie scientifique et technique Albert Blanchard, Paris : 416 pp.
National distribution
Canada
OriginOrigin : Native
Regul arityRegul arity: Regularly occurring
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CurrentlyCurrently : Present
Con fidenceCon fidence: Confident
United States
OriginOrigin : Native
Regul arityRegul arity: Regularly occurring
CurrentlyCurrently : Present
Con fidenceCon fidence: Confident
Description
More info for the term: adventitious
Round-leaved sundew is an insectivorous, short-lived perennial forb
arising from a basal rosette of leaves. The upper surface of the leaf
blades are covered with reddish, glandular hairs tipped with a sticky,
glutinous secretion that traps insects. The inflorescence is a
one-sided raceme with 2 to 15 flowers on a scape that is 2 to 10 inches
(5-25 cm) long. There may be one to seven inflorescences per rosette.
The fruits are capsules with numerous small seeds [8,20,21,41,44].
The root system of round-leaved sundew is usually shallow (less than 2.4
inches [6 cm]) [8]. It consists of a taproot - functional for less than
a year - which is replaced by mostly horizontal adventitious roots with
a few root hairs [8,37,50].
Round-leaved sundew compensates for the low available nutrients in its
habitat by catching and digesting insects [8,45,49,54]. Insects are
caught with the sticky glandular leaf hairs, and the leaf then folds
around the prey. The hairs secrete proteolytic enzymes which digest the
insect and enable the plant to absorb nutrients through its leaves
[37,45,52]. Insect capture is generally believed to enhance growth and
reproduction of round-leaved sundew [8,24,29,46,56]. It is
significantly correlated (p less than 0.01) with total leaf number, number of new
leaves formed, and total leaf area [46]. However, Stewart [50]
determined that round-leaved sundew did not benefit from insect capture
in field experiments in the Jefferson National Forest, Virginia. The
benefits of insectivory may be site-dependent; round-leaved sundew may
benefit most from insect capture on the most nutrient-poor sites.
Synonym
Drosera rotundifolia var. furcata Y. Z. Ruan.
Habitat characteristics
More info for the terms: bryophyte, graminoid, peat, swamp
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Round-leaved sundew is most often found in bogs, but also grows in
swamps, rotting logs, mossy crevices in rocks, or damp sand along
stream, lake, or pond margins [31,37,39,52,59]. It is generally
associated with sphagnum mosses and grows on floating sphagnum mats or
sphagnum hummocks [8,29,32,37,50]. It may also grow on peat soils of
other bryophyte or of graminoid origins [1]. In the northern part
of its range the sphagnum bogs in which round-leaved sundew grows are
generally found surrounding glacial lakes. In the Appalachians from
Pennsylvania to Alabama, the bogs are most often at confluences of
springheads, around seeps, or along streams rather than lake margins.
The same is true for sphagnum bogs of the southeastern coastal plain,
but there round-leaved sundew may also grow in grass-sedge bogs. In the
Pacific Northwest, sphagnum bogs are typically found along streams and
occasionally develop around high elevation seeps and shallow lake
margins in the northern Rocky Mountains [3,45].
Round-leaved sundew is usually confined to sites with a high water table
or high precipitation and humidity [8]. It requires continually moist
or wet situations [20]. Round-leaved sundew grows in organic acid soils
that are low in available nutrients (nitrogen and phosphorous, and
calcium [3,24,49,54]. According to Crowder [8], the normal range of the
water table on sites where round-leaved sundew grows is from 1 inch (2
cm) above to 16 inches (40 cm) below the soil surface. Flooding can be
tolerated for several weeks, but dry periods can only be tolerated for a
very short time. Lloyd [37] reported that it is not found on limestone
soils; high calcium concentrations may be toxic to the plant.
Round-leaved sundew grows in sedge meadow communities of the Huntingdon
Marsh in Quebec on peat underlain by clay at 24 inches (60 cm) or more.
The soil surface is slightly above or up to 10 inches (25 cm) below the
water table [2]. Round-leaved sundew has been reported as growing on
sites ranging from neutral pH (7.3) to very acidic (3.2) [18,38].
Acidic soils with low nutrient concentrations (nitrogen, phosphorous, or
calcium) seem to be the most common substrate [2,11,38,49,61].
In British Columbia, round-leaved sundew is an indicator of wet to very
wet, nitrogen-poor soils in boreal, cool temperate, and cool mesothermal
climates. It is associated with sphagnum moss in nonforested,
semiterrestrial communities [28].
An atypical site was found on Ile Perrot, Quebec, where round-leaved
sundew was growing on moderately dry, abandoned pastureland that
originally had been a swamp. The soil was well-drained loamy sand with
an average pH of 6.1. The site was "basically infertile" with extremely
low calcium and nitrogen concentrations [52].
Associations
In Great Britain and/or Ireland:
Animal / predator
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leaf of Drosera rotundifolia is predator of Diptera
Other: major host/prey
Animal / predator
leaf of Drosera rotundifolia is predator of Coenonympha pamphilus
Other: unusual host/prey
Animal / predator
bladder of Drosera rotundifolia is predator of Anisoptera
Other: unusual host/prey
Fire management considerations
More info for the terms: bog, marsh
Periodic autumn fires can prolong the life of some bogs by inhibiting
the invasion of woody plant species [45].
Round-leaved sundew, along with cattails (Typha spp.), horsetails
(Equisetum spp.), and common buckbean, are present in sedge meadow
communities that are maintained by fire in the Huntingdon Marsh, Quebec.
Fire is used to prevent the invasion of alders and willows [2].
In central Alberta, the burning of bog forests may revert the vegetation
to that of Labrador tea (Ledum spp.)-dominated moors, of which
round-leaved sundew is a component [36].
Phenology
More info on this topic.
More info for the term: hibernaculum
Round-leaved sundew generally flowers from June to September throughout
its range [19,30,39,45]. Flowers open one per day, starting from the
bottom of the inflorescence [50]. Seed dispersal begins in July and
most seeds fall before winter. However, some may be found in dried
capsules in the spring [8]. Round-leaved sundew forms a hibernaculum
(tightly rolled leaf primordia) in the fall. The remaining leaves, and
frequently the roots, die back after the hibernaculum develops. The
hibernaculum opens in April or May of the following year [45,55,62].
Barcode data: drosera rotundifolia
The following is a representative barcode sequence, the centroid of all available sequences for this
species.
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