Lactuca

Poison lettuce (Lactuca virosa ), illustration

The lettuces (Lactuca ) are a genus of flowering plants in the sunflower family ( Asteraceae). The milky sap from which the Latin name lactuca derived, contains bitter compounds that help the plant in the defense against predators and pests; other hand, they determine the palatability of garden salad, the only Lattichart with economic importance. In particular, in Switzerland the binding salad is traded as lettuce. The genus includes about 100 species that are distributed worldwide.

• 5.1 Kinds (selection)

• 6.1 Notes and references

Description

Vegetative characteristics

In Lactuca species is an annual or biennial or rarely perennial herbaceous plants that reach heights of growth from 15 to over 450 cm. They form taproots. All lettuce types contain a whitish milky sap, especially in the stems and inflorescences. The most upright stem is usually branched. The aboveground plant parts can be hairy.

The leaves are borne in basal rosettes or are arranged opposite one another distributed on the stem. The stalked or sitting leaves are simple to pinnately lobed, circular, oval, oblong, lanceolate, linear or filiform. You are at the edge or at the bottom along the midrib ciliate or having spines and the leaf edge is smooth, toothed to more or less lobed. The leaf surfaces may be hairy. Stipules absent.

Generative features

The bloom conditions are separately or together most to many in paniculate or schirmtraubigen total inflorescences. There are sometimes bracts present. The small and narrow, rarely large, basket- shaped partial inflorescences are approximately cylindrical to bell-shaped, swell during the flowering season, and have diameters of 2-5 (rarely to 8 ) mm. Your shell is composed of five to thirteen imbricated bracts more or fewer in two rows, are shorter by deen extreme sometimes. The inflorescence bottom is flat to convex without chaff leaves. The individual flowers are arranged in one or more rows in the basket- shaped part of inflorescence. Every six to fifty flowers are ray florets. The tongue has five corolla lobes, what can clearly be seen that the corolla tube is formed from five petals. The petals often have a yellow, rarely white, bluish to violet color.

The reddish to light brown, white, or purple to black achenes possess one or more ribs on each side and open into an often filiform extended top, sitting on the pappus. The white pappus consists of several rows of simple and equally long hair.

The chromosome number is 2n = 18

Ingredients

Lactuca species present in the leaves and the milky sap mainly water and more or less

• Triterpene compounds and their forming latex-like substances with water, namely α - Lactucerol ( = taraxasterol ) and various esters of β - Lactucerol including Lactucon, Lactucerin ( Fig. 1 and 2); β - amyrin and germanicol;
• Bitter substances with sesquiterpene lactone - basic structure, mainly Lactucin and Lactucopikrin ( see Fig, 3 and 4 ), as well as their oxalates and sulfates. There are probably this group substances which may also contact allergy, which can cause allergic salad;
• The phytoalexin Lettucenin A, also with sesquiterpene basic structure, which has antifungal properties;
• The dyes vitamin A and Lactucaxanthin and the flavonoids quercetin, apigenin, luteolin and Lutolin;
• The essential oil coumarin, which contributes to the taste;
• Minerals, vitamin K1.

The seeds contained in the sterol fraction, among other β -sitosterol and campesterol. The root in addition to Lactucin and Lactucopikrin contains other bitter substances with similar structure, eg Jacquinelin. The lettuces contain no alkaloids.

Pharmacology

As regards the effects of the ingredients of lettuces, you know lately, from a laboratory study that the main bitter compounds Lactucin and lactucopicrin act falciparum against the causative agent of malaria, Plasmodium and this effect is ethno- biologically known in Afghanistan - only no Lattichart is used there, but the common chicory (Cichorium intybus ), which contains the same two substances.

Herbalism claims that the cos - milk juice is said to have a calming and sleep-inducing effect, the scientific evidence is still pending (see Poison cos # pharmacology ).

Dissemination

There are about ten Cos species in North America, 33 in tropical East Africa, 40 in Asia and 17 in Europe. European species grow in temperate and warm regions. The northern boundary runs approximately at 50 ° to 55 ° north latitude, with the exception of L. sibirica, which can occur up to 70 degrees. The western species is L. tatarica at 9 ° West. Most species live at altitudes of 200 to 600 meters with exceptions up to 2000 meters (L. alpestris, L. tatarica, L. altaica, and L. tenerrima ). Most European species occur in the Mediterranean, many of them only there.

During an excursion through parts of Central Europe, especially L. serriola was found. Only in Provence and Italy, there was a greater diversity of species. It should be remembered, however, that the lines of the excursion, for example, the Rhine-Main -Moselle area not touched, where several rarer species are native.

System

There are about 100 species of Lactuca.

Some lettuce types are visually difficult to distinguish, such as the members of the group L. serriola / L. saligna / L. virosa. Moreover, according to recent studies, the members of the group L. sativa / L. serriola / L. dregeana / L. altaica genetically have no differences, and we probably are conspecific.

A division often used is the. Gene pool in which are grouped around the garden salad Here are the primary gene pool for the salad the species L. serriola / L. dregeana / L. altaica, and L. aculeata. These can easily be crossed with sativa L. and thus provide a readily available source for lettuce improvement, since the secondary gene pool consists of L. saligna and L. virosa, here the intersection is difficult. At the tertiary gene pool eventually crossing is possible only with radical methods; it consists of the types of sections Phaenixopus, Mulgedium and Lactucopsis (see below).

Types (selection)

The 17 species occurring in Europe are divided into several sections and subsections:

• Section Phaenixopus: The inflorescence is pyramidal or spike -like with single or standing in tufts basket. Head with four to eight flowers. Lactuca acanthifolia ( Willd.) Boiss. Endemic to Greece, Crete, Turkey.
• Lactuca longidentata Moris: Endemic in Sardinia.
• Rod lettuce (Lactuca viminea J. et C. Presl. ): Domestic, Europe, Asia, North Africa.

• Lactuca sibirica Benth. ex Maxim. homeland is the north of Europe and Asia, North America.
• Tatar lettuce (Lactuca tatarica CAMey. ): Home is North West and Central Europe, Southwest Asia.

• Lactuca aurea ( Schultz-Bip. ex Panc. ) Stebbins: Endemic on the Balkan Peninsula.
• Oak lettuce (Lactuca quercina L.): History is Southeastern Europe, Asia Minor.
• Lactuca watsoniana Trelease: Endemic to the Azores.

• Subsection Lactuca. These species are ruderal and prefer troubled soils.

• Garden salad, cultivated lettuce (Lactuca sativa L.)
• Spiked lettuce (Lactuca serriola L.): Domestic, Europe, Asia, Africa, North America, Argentina. This type is the most common by far in Central Europe.
• Willow lettuce (Lactuca saligna L.): Domestic, Europe (except north), North Africa, Asia Minor.
• Poison lettuce (Lactuca virosa L.): home is the sub - Mediterranean Europe, West Asia, North Africa, North America.
• Lactuca altaica fish. C. A. et Mey. Homeland is South-East Russia, Central and Southwest Asia.
• Lactuca livida Boiss. et Reut. Endemic in central Spain. Lactuca perennis

• Blue lettuce (Lactuca perennis L.): home is the sub-Mediterranean Europe.
• Lactuca graeca Boiss. Endemic to Greece.
• Lactuca tenerrima Pourr. Homeland is the western Mediterranean, Morocco.

In North America, there are the following ten ways:

• Lactuca canadensis L.
• Lactuca graminifolia Michx.
• Lactuca ludoviciana ( Nuttall ) Riddell
• Lactuca saligna L.
• Lactuca sativa L.
• Lactuca serriola L.
• Lactuca virosa L.

Swell

• John L. Strother: Lactuca. In: Flora of North America Editorial Committee ( eds.): Flora of North America North of Mexico. Volume 19: Magnoliophyta: unranked, part 6: Asteraceae, part 1 ( Mutisieae - Anthemideae ), Oxford University Press, New York / Oxford et al 2006, ISBN 0-19-530563-9, p 258, online.