Api-api Ludat (Avicennia officinalis)

The Api-api Ludat (Avicennia officinalis) is a nationally common mangrove tree from the family Acanthaceae. "Api-api" means "fire-fire" or "firefly" in Malay, as some Avicennia species are noted to attract fireflies.


It is commonly found in most, if not all, the mangrove forests of Singapore.


It usually occurs on the landward side of mangrove forests, and sometimes, along tidal rivers and at their estuaries. The trunk is yellowish-green to brownish-grey.


Like other Avicennia species, it has pencil-like aerial roots (pneumatophores) to help the plant breathes air, which is scarce in the waterlogged soil. The roots spread over a wide area to help stabilise the tree on the unstable ground. These roots reportedly also trap sediments and hence reclaim land naturally.

Research indicated that roots of Avicennia species also exclude salt from entering the plant. For some species, salt filtration by the roots is by far the most important salt-rejecting mechanism, excluding up to 80% of the salt carried towards the root surface by the transpiration stream.


It has simple, opposite leaves with rounded tips. They are bright to dark green on the top side, and light green on the underside. Unlike the other native Avicennia species, the salt glands are on the topsides of the leaves. They excrete part of the remaining quantity of salt which was not excluded at the roots.


Like the other Avicennia species, it has small yellow flowers, occurring in clusters.


The fruits are broadly ovate with a short beak, covered with short hair, and yellowish-brown in colour. The plant exhibits cryptovivipary - the embryo grows to break through the seed coat but not the fruit wall before it splits open. Occasionally, vivipary is also observed, where the embryo grows and break through the seed coat and the fruit wall while still attached to the parent plant.

The wood is used as firewood, and the fruits are edible.

References

• Chong, K. Y., H. T. W. Tan & R. T. Corlett, 2009. A Checklist of the Total Vascular Plant Flora of Singapore: Native, Naturalised and Cultivated Species. Raffles Museum of Biodiversity Research, National University of Singapore. Singapore. 273 pp.
• Drennan, P., & N. W. Pammenter. 1982. Physiology of salt excretion in the mangrove Avicennia marina (Forsk.) Vierh. New Phytol. 91:597-606.
• Giesen, W., S. Wulffraat, M. Zieren & L. Scholten. 2006. Mangrove guidebook for Southeast Asia. RAP Publication 2006/07. FAO Regional Office for Asia and the Pacific & Wetlands International. Bangkok. 769 pp.
• Ng, P. K. L., and N. Sivasothi. 1999. A guide to the mangroves of Singapore 1 : the ecosystem & plant diversity. Singapore Science Centre. Singapore. 168 pp.
• Scholander, P. F., H. T. Hammel, E. Hemmingsen, & W. Garey. 1962. Salt balance in mangroves. Plant Physiology. 37:722-729.
• Waisel, Y., A. Eshel and M. Agami. 1986. Salt balance of leaves of the mangrove Avicennia marina. Physiologia Plantaruma. 67:67--72.