Shrub lettuce

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Shrub lettuce
Bush lettuce on Fuerteventura

Bush lettuce on Fuerteventura

Systematics
Order : Astern-like (Asterales)
Family : Daisy family (Asteraceae)
Subfamily : Cichorioideae
Tribe : Cichorieae
Genre : Thorn lettuce ( Launaea )
Type : Shrub lettuce
Scientific name
Launaea arborescens
( Batt. ) Murb.

The bush Dornlattich ( Launaea arborescens , Syn. : Zollikoferia arborescens . Batt ) is a plant type from the genus of Dornlattiche ( Launaea ). The medium-sized thorn bush with its conspicuously zigzag-shaped branches grows in the semi-deserts of northwest Africa, on the African Atlantic coast and the offshore islands as well as in southeast Spain. The specific epithet “arborescens” ( Latin “tree-like”) indicates its shrub-like growth.

description

Launaea arborescens is a medium-sized, very finely branched shrub heavily armed with thorns, approximately hemispherical to pillow-shaped, reaching heights of 50 to 100 cm, up to a maximum of 150 cm.

The zigzag growth of the shoot axes is striking . These are smooth when young, of uniform thickness, gray-green in color and covered by a thin, wipeable layer of wax ( glauk ); they get a gray-brown bark when old. Even the young shoot axes are rigid and slightly lignified by sclerenchymal fibers . They branch out after short distances at angles of 80–100 ° and thus form densely branched axis systems that penetrate each other and end in flowers or thorns at the ends. Both the shoot axes and the leaves have an unpleasant smelling milky sap .

The shrub is largely leafless and only bears a few leaves during the main bloom in the rainy season in autumn or winter. These are mainly located at the base of the vegetative shoots used to grow in size, but are soon thrown off again when the water supply decreases. The up to 8 cm long equifacial leaves are up to 0.5 cm wide and linear-lanceolate, sometimes somewhat wider and then irregularly lobed and serrated, some lobes sometimes long and narrow. Only small, triangular scale leaves are found on the generative shoot axes of the inflorescences .

The yellow daisy flowers with a diameter of about 1.5 cm always sit individually at the end of the stem axes of the total inflorescences. The 9-13 bracts , layered like a roof tile, are weakly ciliated at the tip and are about one centimeter long. On the buds, the bracts form a slender cylinder, which widens slightly bell-shaped at the bottom when flowering. During the ripening period, they close conically and finally open in a star shape when the fruit is ripe. In the flower head there are 7–19 ray- florets , the 5–8 mm long and 2.5 mm wide tongues of which terminate in five lobes, which reveal their formation from five interconnected petals . The anthers of the stamen are as Compositae fused common to a tube through which the stylus of the plunger extends. Above the tube, the stamp divides into two scars . The stamens, pistils and pollen are bright yellow like the flower tongues. The pollen own, as with all Dornlattichen, three composite germ openings surrounded by thorny ridges (tricolporate-echinolophat).

The light brown achenes are three to four mm long and 0.7–1.3 mm in diameter. They are structured by five longitudinal ribs, which in turn are accompanied on both sides by less pronounced secondary ribs. At the upper end there is a white, about five to eight mm long sessile parachute ( pappus ) made of bristle-like to downy hair.

The twofold ( diploid ) chromosome set of the shrub lettuce has a chromosome number of 2n = 14.

Occurrence

Distribution area according to Kilian, 1997

The shrub thorn lettuce is native to the north-west of the Sahara in Morocco , Algeria , Western Sahara and Mauritania . It can also be found on most of the islands of Macaronesia in drier locations, especially on Cape Verde and the Canary Islands , preferably on the eastern islands of Fuerteventura and Lanzarote . Another area of ​​distribution are the dry coastal steppes in southeast Spain in the provinces of Granada , Almería and Murcia .

In the phytosociology the vegetation of the Canary the shrub-Dornlattich is the characteristic species of plants society dry bush (Launaeetum arborescentis) on Fuerteventura covered over two-thirds of the island surface, it is therefore one of the landscape formative species of this island.

ecology

Launaea arborescens is xerophilic : it prefers dry, semi-desert-like locations with sandy to stony soils. Year-round temperatures above zero and annual precipitation up to a maximum of 400 mm characterize its distribution area (for comparison: in Munich the annual mean precipitation is almost 1000 mm). Locations with precipitation below 300 mm are preferred, in the interior of North Africa even regions are still settled in which less than 40 mm of precipitation is available per year. The distribution area includes many coastal regions and island locations in which, despite the low rainfall, comparatively high humidity and moderate temperatures prevail ( cold coastal deserts ).

Section through a shoot (200x).
Ca: cambium , Cu: cuticula , Ep: epidermis , Hyp: hypodermis with the green chloroplasts , Pl: phloem , RP: cortical parenchyma , Skl: sclerenchyma , T: trachea / tracheid , Xl: xylem
Cut through the leaf (100x).
Ap: assimilation parenchyma , Cu: cuticle , Ep: epidermis , Lbs: vascular bundle sheath, Nlb: secondary
vascular bundle , Pl: phloem , St: stoma , Xl: xylem

As a xerophyte, the shrub lettuce is often adapted to drought and pursues various strategies to counteract the lack of water. It has a pronounced tap root , which can reach a length of more than 170 cm in a 90 cm high plant and has strong side roots. With this root system, it can tap the deeper and regularly renewed water reserves , especially in the interior of the country, where it prefers to settle in dried-up stream beds and wadis .

A further adaptation is the extensive renouncement of leaves and the associated reduction in the area that evaporates water. Leaves only form on the shrub during periods of higher rainfall, but they are quickly shed off again when water is scarce. The function of the leaves is taken over by the young, green shoot axes, in which in the hypodermis , i.e. the cell layers lying directly below the surface , a pronounced tissue with numerous chloroplasts for photosynthesis ( assimilation parenchyma ) can be found, which makes the essential contribution to energy and metabolism of the plant. The leaves also reduce the surface area due to their equilateral ( equifacial ) structure, as they offer optimal assimilation performance on a small area thanks to the possibility of photosynthesis on both the upper and lower side of the leaf.

Unusual for a plant in such dry locations is the spreading strategy of the shrub thorn lettuce, which blooms and produces fruit all year round if there is sufficient water supply. These do not have any dormancy , but rather begin to germinate under favorable conditions; a wide temperature range is accepted. A germ depot in the soil, which ensures the repopulation of the site after extreme drought, can therefore not be built. In addition to spreading via seeds, the shrub lettuce also spreads vegetatively and forms offshoots via its side roots. With good conditions, it can build up extensive stocks in a relatively short time.

Pollination by a sand bee

The flowers of the shrub lettuce are pollinated by bees, the seeds are spread by the wind with the help of the pappus ( umbrella flyer ). The flower then dies and is thrown off, the remaining terminal shoot is transformed into a thorn. After germination, the young plants first form a rosette of leaves on the ground, from which the main shoot grows, which quickly branches into an inflorescence. Further growth takes place via secondary shoots that arise at the base of the main shoot ( sympodial growth ). These repeat the principle of the first shoot, and in turn form inflorescences and one or two innovation shoots at the base, even an initial leaf is often rosetted. From the dormant buds on the base of the main shoot, which is initially strongly compressed by the formation of the rosette, new side shoots form as the growth continues. A strong, compact, strongly woody permanent axis system is created inside the shrub, which is overgrown by the interpenetrating thorny inflorescences. These remain green after the actual flowering period for a good year before they die, but then remain on the shrub.

In the south of Spain, the thorn lettuce is parasitized by the gall wasp species Aulacidea martae , which was first described in Cabo de Gata ( Almería ) in 2004 by José Luis Nieves-Aldrey. The wasp, barely two millimeters long and largely black in color, lays its eggs exclusively in the shoot axes of the shrub lettuce. However, the bile develops completely inside the shoot without causing any external swelling. The larvae develop in three millimeter long chambers and finally pupate in February; After the wasps hatch, you can see the small, circular holes through which the wasp leaves the plant.

The shrub lettuce is not included in the Red List of Endangered Species ; according to the criteria of the International Union for Conservation of Nature (IUCN), the shrub lettuce is not endangered.

use

The shrub lettuce is not used economically. In the African distribution area, despite its thorns , it is mainly grazed by camels in the dry season , but is not well tolerated in larger quantities because of its ingredients.

In traditional medicine , its use as a medicinal plant against diarrhea and as an antispasmodic is known, the milk juice is used to treat skin diseases. In addition, the use of a light infusion against worm diseases is mentioned, especially in children. In the region around Marrakech (Morocco), the powdered root of the shrub lettuce is administered together with Artemisia herba-alba for diabetes .

An alcoholic extract from Launaea arborescens proved in the laboratory to be an effective remedy against eggs of the roundworms of the genus Globodera , which are important pests of plants; a practical application does not yet exist.

Among other things, the coumarins esculetin and cichoriin , several flavonoids such as luteolin , a lignan as well as caffeic acid ethyl ester and ferulic acid were detected.

Systematics and history

Herbarium document for Zollikoferia arborescens Batt. , Jules Aimé Battandier (1888)



 Launaea hafunensis



   


 Launaea spinosa


   

 Launaea arborescens



   

 Launaea acanthodes


   

 Launaea polydichomata





Genus Launaea Section Acanthosonchus
systematics according to Kilian (1997)

The first, little-noticed description of the shrub lettuce comes from the year 1823 by the biologist Thomas Edward Bowdich , who described the species on the Cape Verdean island of Boa Vista as a new species Prenanthes spinosa in the genus of the hare lettuce ( Prenanthes ). However, this naming is not valid according to the international rules for naming , as the botanist Peter Forsskål had already used this name for the closely related species Launaea spinosa , and it was published in 1775. The herbarium Bowdichs also lost on the way back.

Launaea arborescens was largely identified in the 19th century with the current species Launaea spinosa . In 1888 the French botanists Jules Aimé Battandier and Louis Trabut recognized the shrub lettuce as an independent species on a research trip through Algeria; Battandier then described Launaea arborescens as a new species Zollikoferia arborescens Batt. In 1923 the species was finally classified in the genus Launaea by the Swedish botanist Svante Samuel Murbeck . The combination Launaea arborescens for the thorn lettuce, published by René Maire as early as 1916 , does not meet the necessary criteria for the official naming of a species, but the attribution Maire is often used, especially in French-language literature.

After the last revision of the genus Launaea in 1997 by Norbert Kilian, the shrub thorn lettuce is in the Acanthosonchus section , a group of five shrubs or semi-shrubs with more or less thorny inflorescences. There are no known subspecies of the shrub lettuce. The closest related species is the sister taxon Launaea spinosa , which is native to the north of the Red Sea .

The shrub lettuce is known in its area of ​​distribution by numerous local names, such as Arabic moulbina or bou chlaba, Spanish aulaga, rascamoños or pendejo and carqueja in Portuguese .

The genus name Launaea honors Jean Claude Mien Mordant de Launey (approx. 1750-1816), a French lawyer and scientist, the genus Zollikoferia is named after Caspar Tobias Zollikofer (1774-1843), a Swiss doctor, pharmacist and naturalist.

The bush lettuce in art and literature

Aulaga sculpture in Pájara (Fuerteventura)

The Spanish poet, philosopher and politician Miguel de Unamuno was exiled to the Canary Island of Fuerteventura for a few months in February 1924 because of his journalistic activities directed against the military government of Miguel Primo de Rivera . He processed the experience of exile in his essays , articles and sonnets . Far away from Spain, in the isolation of this barren yet grandiose landscape, he found a new relationship to religion, but also to his own ideal of Spain.

Again and again he describes the stone, treeless landscape of Fuerteventura as the “skeleton of an island” through which the “ verdad desnuda y descarnada, el esqueleto de la verdad ” (German: “the naked and undisguised truth, the skeleton of truth”) speaks. In the omnipresent aulaga - the Spanish name of the shrub lettuce - he finds a symbol for this landscape, because it is itself an " esqueleto de planta, toda ella secas espinas y, por breve tiempo, flores " (German: "skeleton of a plant , very dry thorn and, for a short time, blossoms ”). He dedicated the Aulaga the essay La Aulaga majorera :

«¡Que lección de estilo, y de lo más íntimo del estilo, esta aulaga de Fuerteventura! It la expression de la isla misma; es la isla expresándose, diciéndose; it la palabra suprema de la isla. En la aulaga ha expresado sus entrañas volcánicas, el poso de su corazón de fuego, this isla entrañable. "

- Miguel de Unamuno : La aulaga majorera

In Pájara on Fuerteventura, a monumental, abstract sculpture of a shrub lettuce adorns a roundabout .

Web links

Commons : Bush lettuce ( Launaea arborescens )  - Collection of images, videos and audio files

literature

Individual evidence

  1. For further synonyms cf. Catalog of Life : Launaea arborescens (Batt.) Murb. M. Hassler (2107), World Plants: Synonymic Checklists of the Vascular Plants of the World (version Jan 2017).
  2. ^ Zone KLE I, 1b: Launaeetum arborescentis , based on: Per Sunding: The Vegetation of Gran Canaria. Universitetsforlaget, Oslo 1972.
  3. F. Reiner Ehrig: The main vegetation units of the Canary Islands in a bioclimatic context. In: B. Higelke (Ed.): Contributions to coastal and marine geography . Kieler Geographische Schriften , Vol. 97, 1998, pp. 67–115, table p. 70 and p. 75.
  4. cf. Jörg Weiß: Pretty on the ball - Launaea arborescens. Forum of the Microscopic College Bonn, April 6, 2014 (with numerous microscopic sections).
  5. Wolfgang Schütz and Per Milberg: Seed germination in Launaea arborescens: a continuously flowering semi-desert shrub. In: Journal of Arid Environments. Vol. 36, 1997, pp. 113-122.
  6. José Luis Nieves-Aldrey: A New Aulacidea Species (Hymenoptera, Cynipidae) from Cabo De Gata Nature Park (Spain) Inducing Galls on Launaea Arborescens. In: Graellsia. Vol. 60 (2), 2004, pp. 175-184, doi: 10.3989 / graellsia.2004.v60.i2.213 .
  7. a b c d Launaea arborescens (Batt.) Maire, data sheet (PDF) in the IUCN Database for North African Medicinal and Aromatic Plants , accessed on October 23, 2016.
  8. cf. for example Launaea arborescens as pasture for camels in Maroc, 2013. Scribd.com.
  9. a b Ammar Dibi and Fatma Bitam: Phytochemical Study of the Plant Launaea Arborescens. (PDF) In: International Conference on Chemical, Environmental and Biological Sciences (ICCEBS), Penang, Malaysia, 2012. p. 51.
  10. Souad Ziane, Linda Rouissat and Abdelkrim Cheriti: Effet des extraits de quelques Astéraceae (Launaea arboresens et Warionia saharae) sur quelques nématodes à kyste (Globodera sp). In: PhytoChem & BioSub Journal. Vol. 8, No. 2, 2014, pp. 117–121.
  11. Abdelkrim Cheriti, Nasser Belboukhari, et al .: Phytochemical and biological studies on Launaea Cass. genus (Asteraceae) from Algerian Sahara. In: Current Topics in Phytochemistry. Vol. 11, 2012, pp. 67-80, pp. 69-71, 77-78.
  12. cf. also in the following Kilian: Die Lactuceae der Cape Verde Islands, 1988, p. 137; Prenanthes spinosa was published posthumously by Sarah Bowdich: Excursions in Madeira and Porto Santo. London 1825, p. 245 : "Prenanthes -, new species, P. spinosa (?) Bowdich ".
  13. Launaea arborescens from Waste (Spanish), accessed on October 12, 2016.
  14. Kilian: Die Lactuceae der Cape Verde Islands , 1988, p. 122.
  15. Lotte Burkhardt: Directory of eponymous plant names . Botanic Garden and Botanical Museum Berlin, Free University Berlin Berlin 2016. ISBN 978-3-946292-10-4 . doi : 10.3372 / epolist2016
  16. ^ Anne Kraume: The Europe of literature: writers look to the continent (1815-1945) . De Gruyter, Berlin / New York 2010, pp. 126–140: Miguel de Unamuno: Agony of Christianity. Fuerteventura.
  17. Palabra de verdad (1924): "Fuerteventura dice al hombre, dice a sus hombres, a sus hijos, la verdad desnuda y descarnada, el esqueleto de la verdad." In: Miguel de Unamuno: Artículos y Discursos sobre Canarias. Puerto del Rosario 1980, p. 73.
  18. quoted from José Antonio Serrano Segura: Unamuno, el viajero. Los paisajes del alma. March 9, 2015 (Spanish, accessed November 24, 2016).
  19. La aulaga majorera (1924, excerpt). In: Miguel de Unamuno. Obras completas. Escelicer, Madrid 1966, Volume 1, p. 556 (on the title: Majoreros is what the people of Fuerteventura call themselves).