Metroxylon
| Metroxylon | ||||||||||||
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Sago Palm ( Metroxylon sagu ) |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Metroxylon | ||||||||||||
| Rottb. |
Metroxylon is a palm genus native to the western Pacific. Starch is obtainedfrom the sago palm ( Metroxylon sagu ) and other species,which are widespread throughout Southeast Asia. Metroxylon is the only genus of the subtribe Metroxylinae .
features
The representatives are large, tree-shaped palms that grow individually or in groups. They are reinforced or unreinforced and can bloom once ( hapaxanth ) or several times. The trunk is upright and partially covered by the leaf bases that remain on the plant after it has died. At the internodes, adventitious roots sometimes arise , which are usually thorn-like. The bark of the trunk is hard, the pulp is soft and rich in starch .
The number of chromosomes is 2n = 26.
leaves
The leaves are large, pinnate and usually remain on the plant after they die (marzescence). The leaf sheath tears opposite the petiole , is unreinforced or reinforced with partial whorls of rather thin spines, which are united at the base and form a kind of collar. The petiole is well developed, unreinforced or reinforced like the sheath. The upper side of the handle is grooved in the area near the trunk, rounded further up, the underside is continuously rounded. The rhachis resembles the petiole, but is angular on the top. The numerous leaflets are simply folded, linear and are at regular intervals or in groups. They then stand in groups like a fan and give the leaves a feathery appearance. Along the leaf margins and the main nerves they are covered with inconspicuous, short thorns. The central ribs are clearly visible on the top.
Inflorescences
The inflorescences are double branched and are either between the leaves (in the case of the pleonanthic Metroxylon amicarum ) or grouped as a compound inflorescence standing above the leaves. Here the side branches correspond to a single inflorescence, it arises in the axilla of a reduced leaf or a bract . The inflorescence stalk is very short, the cover sheet is tubular, narrowly sheathed, two-keeled and bilobed. There are one to several tubular bracts on the peduncle. The inflorescence axis is much longer than the stem. The bracts on the axis are approximately two-lined (distich), they are tubular, narrowly divided, are unarmed or rarely have a few spines.
The lateral axes of the first order are horizontal to pendulous, each has a basal, tubular, double-keeled, double-lobed, empty front sheet and closely spaced, tubular bracts that are almost spaced apart. All but the bottom one to three carry kitten-like rachillae. The rachillae are cylindrical, with a short, free part followed by a dense spiral of bracts. The lowest and uppermost bracts are empty, in the rest there are dyads consisting of a small male and a similar hermaphrodite flower . In the bud stage, the dyad is covered by thick hair, only in Metroxylon amicarum the hair is sparse. The front leaf of each dyad is tubular, two-keeled and with two triangular lapes, and usually densely hairy on the outside. The Brakteole is two-keeled and densely hairy.
blossoms
The male flowers open before the hermaphrodite. Your cup is tubular and ends with three triangular lobes. The crown is usually twice as long as the calyx, about two thirds of its length divided into three valvate , smooth petals with triangular tips. The six stamens are at the base of the petals, their filaments are fleshy. The anthers are medifix , oblong, and latrors . In the middle of the flower there is a conical rudiment of pistils. The pollen is ellipsoidal and bisymmetrical. The germ openings are equatorial disulcat.
The hermaphrodite flowers are superficially similar to the male ones, but are fatter. The calyx, crown and stamens resemble those of the male flowers. However, the filaments are united at the lower end to a tube that the ovary encloses. The gynoeceum consists of three carpels, each with an ovule . It is rounded and covered with vertical rows of small scales. The stylus is conical and has three grain edges . The ovules are basal and anatropic.
Fruits and seeds
The fruit is round, usually large, and contains a seed. Scars are apical. The exocarp is covered with vertical rows of straw-colored to chestnut-colored scales pointing backwards. The mesocarp is quite thick, cork-like to spongy. An endocarp is not developed. The seed is spherical, sits basal. It is deeply indented at the tip. He is wrapped in a thin to thick sarcotesta . The endosperm is homogeneous. The embryo is basal.
Distribution and locations
The genus is native to eastern Malesia , the Solomon Islands , the New Hebrides , Samoa , Fiji and the Carolines . A species that is widespread today, the sago palm, is assumed to be the original distribution area of New Guinea and the Moluccas , but is now cultivated and naturalized throughout Southeast Asia.
Most species grow in lowland swamps, where they often grow in groups of numerous individuals. Metroxylon amicarum is also found in deep valleys and high in the mountains of Micronesia .
Systematics
The genus Metroxylon Rottb. is placed within the family Arecaceae in the subfamily Calamoideae and in the tribe Calameae . She alone forms the subtribe Metroxylinae. Metroxylon is a monophyletic group.
The Royal Botanic Gardens, Kew's World Checklist of Selected Plant Families recognizes the following species:
- Metroxylon amicarum ( H. Wendl .) Hook.f. : The home is Micronesia with Pohnpei and Chuuk .
- Metroxylon paulcoxii McClatchey : The home is the western Samoan islands .
- Sago Palm ( Metroxylon sagu Rottb. ): The home is the Moluccas and New Guinea.
- Metroxylon salomonense (Warb.) Becc. : The home is eastern New Guinea to Vanuatu .
- Metroxylon upoluense Becc. : The homeland are the Samoan Islands .
- Metroxylon vitiense (H. Wendl.) Hook.f. : The home is Fiji and Wallis and Futuna .
- Metroxylon warburgii (Heimerl) Becc. : The homeland is the southwest Pacific with the Samoan Islands and Vanuatu .
use
The two main uses of the Metroxylon species are the extraction of sago (starch) from the pulp of the trunks and the extraction of building material for house construction: the leaves are used for roofing, the split leaf stalks are used to make woven walls.
supporting documents
- John Dransfield, Natalie W. Uhl, Conny B. Asmussen, William J. Baker, Madeline M. Harley, Carl E. Lewis: Genera Palmarum. The Evolution and Classification of Palms . Second edition, Royal Botanic Gardens, Kew 2008, ISBN 978-1-84246-182-2 , pp. 176-178.
Individual evidence
- ↑ Rafaël Govaerts (Ed.): Metroxylon. In: World Checklist of Selected Plant Families (WCSP) - The Board of Trustees of the Royal Botanic Gardens, Kew . Retrieved November 7, 2014.
Web links
- Metroxylon on the homepage of the Fairchild Tropical Botanic Garden