Dischidia

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Dischidia
Dischidia nummularia

Dischidia nummularia

Systematics
Euasterids I
Order : Enzianartige (Gentianales)
Family : Dog poison family (Apocynaceae)
Subfamily : Silk plants (Asclepiadoideae)
Tribe : Marsdenieae
Genre : Dischidia
Scientific name
Dischidia
R.Br.

Dischidia , also called urn plants, is a genus of plants in the subfamily of the silk plants (Asclepiadoideae), which belongs to the family of the dog poison plants (Apocynaceae). About 80 species of the genus Dischidia are currentlyknown.

description

Vegetative characteristics

Illustration of Dischidia collyris with shield-shaped leaves (Section Conchophyllum )
Funnel-shaped leaf of Dischidia rafflesiana into which the adventitious roots grow

The species of the genus Dischidia are mostly herbaceous or succulent epiphytes with trailing stem axes , more rarely also epilithic growing, in this case creeping on stones. They usually have pronounced adventitious roots . Otherwise, the roots sit on the nodes ( nodes ). The shoot axes measure 1 to 4 mm in diameter and are glabrous, coarse hairy or tomentose. The milky sap (latex) is white.

The opposite or alternate leaves have only short stems. The leaf blade varies within the genus. There are elongated-elliptical, oval to inverse-lanceolate leaf blades that are flat, lenticular and entire, or round and shield-shaped leaves. The leaf blades are thin and not succulent, or leathery or thickly succulent. A specialty are the species with jug-shaped or tubular leaves (so-called " urn leaves "), which fill up with humus over time and grow into one or two adventitious roots.

Generative characteristics

The many-flowered inflorescence is often racemose , screw-like or divided into partial inflorescences . The flowers usually open asynchronously; only a few open synchronously. Often one inflorescence axis is more or less clearly developed, more rarely several. The flower stalks are short or almost absent. The corolla is relatively narrow and urn-shaped, often very small (a few millimeters), but sometimes also bell-shaped and relatively large. Usually it is white, greenish-white, yellowish-white, cream-colored, slightly reddish, dark red to bluish-green. The flowers of many species of Dischidia also appear closed during anthesis , while in other species the flowers are wide open. The secondary crown is ring-shaped or five-lobed, with the secondary crown lobes alternating with the crown lobes. The corolla lobes are usually two-lobed apically and curved inward. The secondary crown can also be completely absent. The mostly conical gynostegium is seated or pedicled. The stylus head is conical and is enveloped by the anthers . The oblong-oval pollinia stand upright; the caudiculae are usually broadly triangular. The slender, spindle-shaped and bare fruits are round or somewhat flattened and pointed at the end. They stand alone or in pairs. The flattened, brown seeds are oblong to oval and have a tuft of white hair.

The number of chromosomes is (in Dischidia bengalensis Colebr. , Dischidia hirsuta L. and Dischidia nummularia Blume ).

Way of life

The species of the genus Dischidia grow as epiphytes on trees and stones. However, they have very different requirements for light, temperature and humidity. This also reflects their large geographical distribution area and their distribution in the vertical.

Many species of the genus Dischidia live in symbiosis with ants. The ants live in the tubular or pocket-shaped leaves or under the shield-shaped leaves. They carry material into the tubular leaves, into which one or two adventitious roots then grow, which branch out there. The formation of the tubular or urn-shaped leaves in some species also depends on the nutritional status or location of the plant. Well-fertilized plants or plants in a very favorable location may not develop these leaves at all. In other species with leaves that rest on stones like shields or limpets, ants collect material underneath. Here, too, the adventitious roots grow into it. The shield-like leaves have another function: the moisture stays under these leaves for a very long time. They help the plant to survive dry periods. But other species without pocket-like or shield-like leaves also live myrmekophil . The ants collect the seeds and carry them into their tree nests. There the seeds germinate and the seedlings grow from these nests.

The flowers of many Dischidia species also appear closed during the flowering period; only in a few species is the flower fully open. Little is known about the pollination of the flowers. The pollen is not distributed loosely on the stamens, as is the case with many other plants, but rather concentrated in relatively compact pollinia that are transported as a whole from one plant to another. The pollinia are relatively tight and are torn loose by insect legs. The flowers work on the principle of a clamp trap: the insects get caught with their legs in the secondary crown. When trying to break free, the pollinia tear off and stick to the legs. Rintz (1980) suspects that day and night butterflies pollinate the flowers. Jones (2008) observed night and day butterflies, ants, wasps, bees and flies as they sucked up the nectar that the flowers secrete. However, he emphasizes that this does not mean that they are also the pollinators of the flowers.

Occurrence

The Dischidia species occur in Southeast Asia (southern China, the Philippines, Sri Lanka, Thailand, Vietnam, Laos, Indonesia, Malaysia and India), Australia, Oceania and New Guinea. They grow in tropical to subtropical rainforests at altitudes between sea level and about 2000 meters.

Dischidia albiflora
Dischidia bengalensis
Dischidia hirsuta
Dischidia imbricata
Dischidia ovata
Dischidia platyphylla

Systematics

The genus Dischidia was established in 1810 by the British botanist Robert Brown . The type species is Dischidia nummularia R.Br. In the course of research history, some synonyms for Dischidia R.Br. accumulated: Collyris M.Vahl , Conchophyllum Blume , Dischidiopsis Schltr. , Dolichostegia Schltr. , Hoyella Ridl. , Leptostemma flower , Oistonema Schltr. , Spathidolepis Schltr.

Jones distinguishes between three sections:

species

Many species are poorly known and their status is uncertain. Here is a selection of the 119 species of Dischidia :

No longer counted in this genus:

  • Dischidia chinghungensis Tsiang & PTLi => Hoya chinghungensis (Y.Tsiang & PTLi) MGGilbert, PTLi & WDStevens

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literature

  • Focke Albers and Ulli Meve (eds.): Succulent lexicon Volume 3 Asclepiadaceae (silk plants) . 322 pp., Ulmer, Stuttgart 2002, ISBN 978-3-8001-3982-8 .
  • Victor Rico-Gray and Paulo Santos Oliveira: The ecology and evolution of ant-plant interactions. 331 pp., Chicago, University of Chicago Press, 2007 ISBN 978-0-226-71347-2
  • Antone Jones: A look at Dischidia. Stemma, 2 (1), pp. 4–17, 2008 Online (PDF; 4.5 MB)

Online source

Individual evidence

  1. ↑ a b c d Jones (2008: p. 4ff.)
  2. ^ RE Rintz: The peninsular Malaysian species of Dischidia (Asclepiadaceae). In: Blumea , 26: 81-126, Leiden 1980 ISSN  0006-5196
  3. ↑ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar as at au av aw ax ay az ba bb bc bd be bf bg bh bi bj bk bl bm bn bo bp bq br bs bt bu bv bw bx by bz ca cb cc cd ce cf cg ch ci cj ck cl cm cn co cp cq cr cs ct cu cv cw cx cy cz da db dc dd de df dg dh di dj dk dl dm dn do dp dq dr ds dt du dv Rafaël Govaerts (Ed.): Dischidia - World Checklist of Selected Plant Families of the Royal Botanic Gardens, Kew. Last accessed on November 13, 2018.

Web links

Commons : Dischidia  - collection of images, videos and audio files