Rhizophora
| Rhizophora | ||||||||||||
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Branch of Rhizophora racemosa with fruit and ripe seedling in Vigia , Pará , northern Brazil |
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| Scientific name | ||||||||||||
| Rhizophora | ||||||||||||
| L. |
The species of the genus Rhizophora belong together with the not closely related species of the genus Avicennia (subfamily Avicennioideae within the acanthus family ) to the most important mangrove trees . They owe their scientific name to the sweeping, arched stilt roots ( Greek ῥιζο- , rhizo- , "root"; Greek φορός, phorós , "bearing"). The name "red mangrove" is used primarily for the widespread species Rhizophora mangle ; it probably refers to the reddish bast and the sometimes reddish brown wood of this type.
The wood of Rhizophora species is used to extract charcoal and as building material, the bark is used to extract tannins . Controlled use, taking forestry considerations into account, has long been practiced in Malaysia , but is the exception elsewhere.
description
Rhizophora species are trees or shrubs in the intertidal zone of tropical coasts . They have showy stilt roots. The smooth, leather-like leaves are undivided, opposite and have entire margins. There are often numerous lenticels on their underside . A pair of stipules envelops the terminal bud of each shoot; the stipules are shed when the new pair of leaves unfold.
The plants are wind pollinated . The inflorescence arises from the leaf axils and is branched to different degrees in the individual species. The four-fold flowers are radial symmetry . The four sepals are strong and fused at the base. The four petals are mostly hairy and, unlike other Rhizophoraceae, do not have eyelash-shaped appendages; they are shed a short time after the flower opens. The filaments of the eight to twelve stamens are reduced, the modified anthers have numerous pollen sacs . The semi-under permanent ovary has two ovules .
The egg-shaped or conical fruit is brownish or gray-green and leathery hard. As a rule, only one seed develops, which germinates in the fruit on the mother tree ( viviparia ). The primary root dies quickly. The hypocotyl of the seedling breaks through the pericarp , but initially remains connected to the fruit via the cotyledons that have been transformed into a collar-shaped structure . In some species, the seedling can reach more than 50 cm in length before it is shed. The seedlings are buoyant and can drift in the sea for months without losing the ability to take root.
Systematics
6 types are distinguished within the genus :
- Rhizophora apiculata flower : eastern Indo-Pacific
- Rhizophora harrisonii Leechm. : West Africa , Central and South America
- Red mangrove ( Rhizophora mangle L. ): West Africa, North and South America; possibly the morphologically very similar Pacific is Rhizophora samoensis with Rhizophora mangle identical
- Rhizophora mucronata Lam. : East Africa , Indian Ocean , Northern Australia , New Guinea , Philippines
- Rhizophora racemosa G.Mey. : West Africa, South America
- Rhizophora stylosa handle. : Indian Ocean east of India , Pacific to Samoa
In addition, the hybrids Rhizophora × lamarckii Montrouz. ( Rhizophora apiculata × Rhizophora stylosa ) and Rhizophora × selala (Salvoza) Toml. ( Rhizophora stylosa × Rhizophora samoensis ). Even with Rhizophora harrisonii it could be a hybrid ( Rhizophora mangle × Rhizophora racemosa ).
literature
- Philip B. Tomlinson: The Botany of Mangroves. Cambridge University Press, Cambridge et al. 1986, ISBN 0-521-25567-8 .
