Enhalus acoroides   (Linnaeus f.) Rich. ex Steud.  (Seagrass)
Organism information awaits expert curation
Taxonomy
Kingdom:Plantae
Phylum:Magnoliophyta
Class: Equisetopsida
Order:Alismatales
Family:Hydrocharitaceae

Image copyrights: McKenzie et al

Description
Size: upto 2 cm long

Plants robust. Rhizomes creeping, branched or unbranched, stout, upto 2 cm thick, densely covered with persistent fibrous strands of decayed leaves. Roots numerous, cord-like, unbranched, spongy, white. Shoots erect, branched or unbranched, bearing 4-5 leaves at each branch.
Male flowers numerous, enclosed by 2 spathes, arranged densely on conical central axis, white. Peduncle of the male inflorescences flattened, always submerged. Spathes lanceolate, overlapping at base, acute at apex, subequal, wavy along margins and serrulate at the upper half, persistent, with numerous tannin cells, greenish-brown. Midrib prominent with many irregular hairs. Hairs upto 1.5 cm long, subulate, unbranched, stiff. Male flowers globose, white. Pedicels very thin, hyaline, white, breaking at ca 0.5 mm below the flower. Sepals 3, elliptic, entire along margins, concave, hyaline, white. Petals 3, elliptic, subtruncate at base, obtuse at apex, entire along margins, concave, hyaline, white. Both sepals and petals reflexed after anthesis. Stamens 3, erect, minutely stalked. Anthers elliptic, basifixed, 2-celled, with tuberculated outgrowths throughout, each cell contains 2 rows of pollen grains, dehiscing longitudinally. Pollen grains globose, white.
Peduncle of the female inflorescences flattened, dilated at apex, brownish, subtended by 2 equal spathes, after fertilization coiled and contracted below the water level. Spathes linear-oblong, obtuse at apex, entire along margins below, serrulate above, persistent, with numerous tannin cells. Midrib conspicuous, swollen dorsally, grooved ventrally, with irregular long slender hairs towards 1/3 of the apex. Sepals 3, oblong, subtruncate at base, acute at apex, entire, recurved along margins, transparent, reddish-brown, with numerous tannin streaks. Petals 3, linear-oblong, obtuse at apex, crumbled, membranous, with waxy coating and numerous reddish brown tannin streaks. Ovary ovoid, laterally compressed, with minute tuberculated projections at base, densely multibranched flattened appendages at apex, with numerous tannin cells. Ovary enlarged at base, the inner wall at base doom-shaped from where placental lamella arise which completely separate the cavity into 6 partitions. The placenta is 2-layered, transparent. Styles 6, each divided into 2 stigmatic branches. Stigmatic branches 10-12, linear or subulate, acute at apex, with numerous sticky projections on dorsal side and glabrous on ventral side. Ovules many, ellipsoid, minutely stalked, yellow, 1 or 2 attached parietally at each placenta, embedded in viscous fluid.
Fruits ovoid, acuminate at apex, green, densely clothed with numerous erect branched black appendages, with many indistinct longitudinal ribs, opening irregularly at apex. Seeds 10-12, obconical to obovoid, 9-12 cm long, the conical part greenish, and the stout basal part brownish. Testa thin, easily ruptured. Embryo ellipsoid, with conical hypocotyls. Plumule lateral.

The availability of male plants is very rare, whereas, that of female plants is common. This is because, single male inflorescence contains hundreds of minute male flowers which would be sufficient to pollinate a considerable number of female plants. Among all the marine angiosperms, Enhalus acoroides is the only species which shows aerial surface pollination.


Synonym (s)

Common Name (s)
• Alai Vaari (Tamil)
• Olai Paasi (Tamil)
• Kadal Vaari (Tamil)
• Vaataalai (Tamil)
Economic Importance and Threats
Importance:  Commercial
(Seeds are edible; fibre from leaves are used for making fishing nets; the plants are used as manure in coconut and tobacco plantations.
It is potent antifeedant, antibacterial, and antilarval secondary metabolites; flavonoids, as one of the characteristic chemical constituents of this species, may play an important chemical defensive role against predators, competitors, and potential pathogens)

Ecology
Habitat:  Reef Associated, Sandy, Muddy, Coastal

Biogeography


• Tamil Nadu, Manoli Island (Lat: 9.2) (Long: 79.11) INDIA (Record: 09/2006)
• Tamil Nadu, Pudukottai, Kattumavadi INDIA (Record: 20/09/1987) (Depth: 2 mts)
• Tamil Nadu, Pamban INDIA (Record: 14/02/1987, 26/09/1987) (Depth: 2 mts)
• Tamil Nadu, Krusadai Island INDIA (Record: 18/02/1987, 25/09/1987, 21/04/1988, 26/09/1944) (Depth: 1.5-2 mts)
• Tamil Nadu, Mandapam, Kovilvadi INDIA (Record: 20/04/1988) (Depth: 5 mts)
• Kerala INDIA
• Lakshadweep INDIA
• Tamil Nadu INDIA
• Andaman and Nicobar Islands INDIA
• Tamil Nadu, Gulf of Mannar INDIA
• Tamil Nadu, Thonithurai INDIA
• Tamil Nadu, Pamban INDIA
• Tamil Nadu, Krusadai INDIA
• Tamil Nadu, Manoli Island INDIA
• Tamil Nadu, Gulf of Mannar, Hare Island INDIA
• Andaman and Nicobar Islands, Andamans INDIA
• Andaman and Nicobar Islands, Katchall INDIA
• Andaman and Nicobar Islands, Nancowry INDIA
• Tamil Nadu, Pudukottai, Kattumavadi INDIA (Record: 01/1987-09/1988)
• Tamil Nadu, Mandapam INDIA (Record: 01/1987-09/1988)
• Tamil Nadu, Pamban INDIA (Record: 01/1987-09/1988)
• Tamil Nadu, Krusadai Island INDIA (Record: 01/1987-09/1988)

Literature Source(s)
  • Mathews, G; Diraviyaraj, K and Edward, JKP (2008) Seagrass abundance in Manoli Island of the Gulf of Mannar, southeast of India. Proceedings of the national symposium on marine and coastal ecosystems 27-29, August 2007 Seaweed Research and Utilisation Seaweed Research and Utilisation Association 30 59-65 Available at - NIO, Goa
  • Society for the Management of European Biodiversity Data (2009) World Register of Marine Species (WoRMS) Available at - http://www.marinespecies.org
  • Seagrass-Watch Available at - http://www.seagrasswatch.org/home.html
  • Ramamurthy, K; Balakrishnan, NP; Ravikumar, K and Ganesan, R (1992) Seagrasses of Coromandel Coast India Botanical Survey of India, Coimbatore 80 pp Available at - NIO, Goa
  • (2006) Algaebase Available at - http://www.algaebase.org/
  • Jagtap, TG; Komarpant, DS and Rodrigues, R (2003) The seagrasses of India World atlas of seagrasses University of California Press, Berkeley, USA 101-108 Available at - NIO, Goa
  • Rao, DVS; Rao, KS; Iyer, CSP and Chittibabu, P (2008) Possible ecological consequences from the Sethu Samudram Canal Project, India Marine Pollution Bulletin Elsevier 56(2) 170-186 Available at - http://dx.doi.org/10.1016/j.marpolbul.2007.10.018
  • Thangaradjou, T and Kannan, L (2005) Marine sediment texture and distribution of seagrasses in the Gulf of Mannar Biosphere Reserve Seaweed Res Utilis NISCAIR 27(1&2) 145 - 154 Available at - http://www.casmbenvis.nic.in/sdnp/coral%20reef%20pdf/C11.pdf
  • Tanaji,G; Jagtap, Deepali,S; Komarpant, and Rodrigues, RS (2003) Status of a seagrass ecosystem:an ecologically sensitive wetland habitat from India Wetlands 23(1) 161–170 Available at - http://www.springerlink.com/content/awjp1469442q5g75/fulltext.pdf
  • Stoddart, DR and Fosberg, FR (1972) South Indian sand cays Atoll Research Bulletin 161 1-25 Available at - http://si-pddr.si.edu/jspui/bitstream/10088/5054/1/00161.pdf
  • Thangaradjou, T; Nobi, EP; Dilipan, E; Sivakumar, K and Sushila, S (2010) Heavy metal enrichment in seagrasses of Andaman Islands and its implications on the health of the coastal ecosystem Indian Journal of Marine Sciences NISCAIR 39(1) 85-91 Available at - http://nopr.niscair.res.in/bitstream/123456789/8550/1/IJMS%2039%281%29%2085-91.pdf
  • Jagtap, T.G. (1992) Marine flora of Nicobar group of islands in Andaman Sea. Indian Journal of Marine Sciences National Institute of Science Communication & Information Resources 21(1) 56-58 Available at - NIO,Goa
  • Parthasathy, N; Ravikumar, K; Ganesan, R and Ramamurthy, K (1991) Distribution of seagrasses along the coast of Tamil Nadu, Southern India Aquatic botany Elsevier 40(1) 145-153 Available at - NIO, Goa.
  • Jagtap, TG (1991) Distribution of seagrasses along the Indian coast Aquatic Botany Elsevier B.V. 40(1) 379-386 Available at - NIO, Goa

Page last updated on:2011-09-29

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