''Enhalus'' is a monotypic genus of marine

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. They include all forbs (flowering plants without a woody stem), grasses and grass-like plants, a vast majority of ...

s. The sole species is ''Enhalus acoroides''. ''Enhalus'' is a large

seagrass Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families ( Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the ...

native to coastal waters of the tropical Indian and Western Pacific Oceans. It is the only species of seagrass that does aerial surface pollination in which the pollen and the styles remain dry.Phillips, R.C. and E.G. Meñez. 1988. Seagrasses. Smithsonian Contrib. Mar. Sci. 34, 104 pp. ''Enhalus'' is surface pollinated with male

flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechanism ...

s that detach from the plant to float on the surface until they reach a female flower where pollination can occur. Enhalus acoroides is considered a slow-growing, " climax" species.

Description

''Enhalus acoroides'' massive rhizomes (1.5 cm in diameter) help it stay anchored in soft mud substrates, withstanding wave action and tidal currents. it has long strap like leaves (30–150 cm) which make up a significant volume of total plant biomass of shallow water seagrass beds, because of the large structure of the leaves and where they are in the water column, they provide greater surfaces for Epibiont organisms to inhabit. Fruit are round and large (4–6 cm in diameter) with dark, ribbed skin and 6-7 white seeds. The male plant bears a single pedunculate

inflorescence An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed ...

or stem containing clusters of flowers, each is highly reduced in form to a small free floating device. Female Enhalus acoroides bears only a single inflorescence, but the peduncle of a female flower is much longer.

Distribution and habitat

''Enhalus acoroides'' is a

littoral The littoral zone or nearshore is the part of a sea, lake, or river that is close to the shore. In coastal ecology, the littoral zone includes the intertidal zone extending from the high water mark (which is rarely inundated), to coastal areas ...

species living in shallow soft substrates like muddy or sand-flats and coral substrates depending the region of growth. It can be found as far east as

Papua New Guinea Papua New Guinea (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country i ...

and can range from the

Red Sea The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; ...

south to northern Mozambique in the Indian Ocean. It can be found in mixed meadows of seagrasses comprising 90% of the meadow biomass mainly with ''Thallassia hemprichii.'' it can also be found living in isolated areas. Enhalus acoroides grows best just above the level of mean low water springs and grows to generally 4 meters deep.

Reproduction

''Enhalus acoroides'' is

dioecious Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproducti ...

and able to reproduce sexually and asexually. ''Enhalus acoroides'' create small isolated patches containing 25 to 200 shoots through lateral rhizome spreading. It can also produce pollen like other seagrasses but it is unique in that it is the only species of seagrasses that surface pollinates. During this process, the male flower will break off from the spathe and rise to the surface where it has numerous flowers inside its hydrophobic

s. Once at the surface it will release its pollen to a female inflorescence where it has reached the surface of the water by means of an elongated stalk surface. The developing fruit is drawn under the water to finish ripening. Flowering is a year round phenomenon and the amount of flowers being produced are strongly related to variations in mean water temperatures.

References

External links

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Images
of ''Enhalus'' at AlgaeBase {{Taxonbar, from=Q2697339 Hydrocharitaceae Seagrass Hydrocharitaceae genera Monotypic Alismatales genera Dioecious plants