Walnuts

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Walnuts
Real walnut (Juglans regia). Illustration: A) branch with male inflorescences, B) branch with single female flowers, 1 and 2) male flower, 4) female flower, 5) whole fruit, 6) nut

Real walnut ( Juglans regia ). Illustration: A) branch with male inflorescences, B) branch with single female flowers, 1 and 2) male flower, 4) female flower, 5) whole fruit, 6) nut

Systematics
Eudicotyledons
Nuclear eudicotyledons
Rosids
Eurosiden I
Order : Beech-like (Fagales)
Family : Walnuts
Scientific name
Juglandaceae
DC. ex Perleb
Walnut tree in winter
Table top made from solid European walnut wood

The walnut family (Juglandaceae) are a relatively small family of around 60 species of mainly tree-shaped wood plants that belong to the beech-like (Fagales). The family is not at home in Central Europe, the real walnut ( Juglans regia ) is often planted and is widespread wild and naturalized.

description

Vegetative characteristics

The representatives are mainly trees, less often shrubs. They usually contain plenty of tannins . The buds are bare or covered with scales. Terminal buds do occur, but are often displaced by the lateral ones. The leaf scars are large and have three groups of vascular bundle scars . The pith of the branches is firm or chambered.

The leaves are summer or, more rarely, evergreen, usually alternate, less often opposite or whorled. They have no stipules and are paired or unpaired pinnate, usually with 5 to 31 leaflets, rarely they are three-leaved or simple. The leaf margin is whole or serrated. Leaves as well as buds, flowers and fruits are usually provided with resin glands: with yellow or pale, multicellular, shield-shaped glandular scales. They often also have bundled or glandular hair .

Inflorescences

The trees are monocial , more rarely diocesan . The flowers are in catkins or ears , which are usually hanging, rarely upright. Usually male and female flowers are in separate inflorescences, sometimes they are also united in a panicle called androgynous : Here the central spike is female or at least partially female, the side branches bear male flowers. Separately standing male inflorescences are in groups of 3 to 8 catkins or individually. Separate female inflorescences are multi-flowered catkins or two- to multi-flowered spikes. The inflorescences are laterally or terminally on previous year's or older shoots, male inflorescences are sometimes also at the base of this year's shoots. There is only one flower in each bract .

blossoms

Petals are missing. The male flowers have four or fewer (or none) sepals . The unlobed or three-lobed bract and - if present - the two bracteoles are fused with the receptacle of the flower and appear like part of the calyx. The stamens are therefore apparently on the flower envelope and the calyx. The 3 to 40, more rarely up to 100 stamens are sessile, the anthers open with longitudinal slits. A stamp rudiment is rarely available.

In the female flowers of the cup is usually tetralobal, with the ovary grown or he is missing. The bracts and bracts are only fused with the pedicel and the base of the ovary; or with the whole ovary. In some species, individual stamens can be formed in the female flowers. The pistil consists of two carpels, rarely three or four in individual flowers. The ovary stands under, is single-compartment and has a real, incomplete subdivision. Often secondary and tertiary subdivisions occur, so that the ovary in the lower part is two-sided or incorrectly four or eight-sided. Above the middle, the ovary is single-fan, rarely in the uppermost part due to ingrowns in the wall to false five-fan. The ovary contains a single, upright, orthotropic ovule with an integument that stands on top of the primary partition. The placentation is modified at the central angle and appears basal at first glance. A single stylus sits on the ovary , which is rarely missing. The stylus has two to four scar branches .

fruit

There are two types of fruit within the family . The first is a nut fruit that is encased in a fibrous shell attached to the nut that opens or stays closed as it ripens. The second type is a thin-shelled nut, or a thin-skinned nut with two or three wings, or a circular wing. The fruit often resembles a stone fruit , but the shell is formed by the involucrum and the calyx, the thin skin by the calyx alone. However, the shell is never formed by the pericarp, which is why the fruit is not a real stone fruit. This shape of fruit is sometimes called a tryma .

In the fruit sits a single, large seed that is two to four or eight times lobed. One endosperm is missing. The seedling fills the nut. The cotyledons are four-lobed, often fleshy, rich in oil. They often remain in the nut during germination, but can also appear as four-lobed leaves outdoors.

Wood

Walnut wood has been one of the finest furniture woods for centuries. The European walnut is mainly found in the warmer Western and Central Europe. It has a light gray sap that is 3 to 7 cm. The heartwood is dull brown to blackish brown, irregularly pervaded by darker veins of different widths. Wood from France often tends to have a slightly reddish sheen and a particularly even pattern. American walnut is more of a uniform, purple or purple-brown color. Its sapwood is yellowish to light gray-brown. The coloration of all species varies considerably and is highly dependent on age and location. All walnut woods tend to brown and a reduction in color streaking when exposed to strong light. European walnut is harder and heavier than the American species. Walnut is mainly processed into veneer. It is also used to make valuable and elegant furniture. Furniture made from dark American walnut is known as Baltimore Walnut .

As solid wood, walnut wood is used for parquet, rifle stocks and turnery work.

Technical specifications

distribution

The walnut family have their distribution center in the northern hemisphere and occur in America as well as in Eurasia. Most genera are restricted to one side of the Pacific, only Carya and Juglans occur in the Old and New World. Alfaroa and Oreomunnea are restricted to America, the other genera to Asia. Only two genera reach the southern hemisphere with their areas: Juglans reaches northern Argentina, Engelhardia extends to Sumatra, Java and New Guinea. The diversity center is now East Asia, the center of the fossil species diversity, however, is North America.

Systematics

The walnut family in the narrower sense are the sister group of the Rhoipteleaceae within the order Fagales . It is divided into two subfamilies and includes around 60 species. 8 genera are generally recognized, the classification of some species as independent genera is currently under discussion:

  • Subfamily Engelhardioideae Ilyinsk.
  • Subfamily Juglandoideae
    • Tribe Platycaryeae Nakai
    • Tribe Juglandeae Nakai
      • Subtribus Juglandinae DEStone & PSManos
      • Subtribus Caryinae DEStone & PSManos
        • Genus Hickory ( Carya Nutt. )
        • (Genus Annamocarya A. Chev. - position as a separate genus uncertain)

In 2009 the Angiosperm Phylogeny Group owned the genus Rhoiptelea Diels & Hand.-Mazz, which for a while was a family of its own . again included in the Juglandaceae family.

supporting documents

Individual evidence

  1. ↑ walnut. on: schreiner-seiten.de
  2. ^ Paul S. Manos, Donald E. Stone: Evolution, Phylogeny, and Systematics of the Juglandaceae. In: Annals of the Missouri Botanical Garden. Volume 88, No. 2, 2001, pp. 231-269, ( digitized version http: //vorlage_digitalisat.test/1%3Dhttp%3A%2F%2Fbiodiversitylibrary.org%2Fpage%2F26843771~GB%3D~IA%3D~MDZ%3D%0A~SZ%3D~ double-sided%3D~LT%3D~ PUR% 3D).
  3. ↑ Angiosperm Phylogeny Group : An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III. In: Botanical Journal of the Linnean Society. Volume 161, No. 2, 2009, pp. 105-121, DOI: 10.1111 / j.1095-8339.2009.00996.x .

further reading

  • Horst Schaarschmidt: The walnut plants (= The new Brehm library. Volume 591). 2. revised Edition. Westarp Sciences, Hohenwarsleben 1999, ISBN 3-89432-311-6 .
  • Frei Jonas: The walnut, all species cultivated in Central Europe, botany, history, culture . AT Verlag, Aarau. 2019 ISBN 978-3-03902-021-8

Web links

Commons : Walnut Family (Juglandaceae)  - Collection of images, videos, and audio files