The Api-api Putih (Avicennia alba) is a locally 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 can be commonly found at most, if not all, of our mangrove forests, such as Pulau Ubin, Pulau Tekong, Mandai, Pasir Ris, Pulau Semakau, St John's Island, Sungei Buloh Wetland Reserve and Pandan Mangrove.
It is a pioneering species, occurring in mangrove swamps, along seashores and tidal rivers.
The trunk is usually greyish brown in colour. 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 pointed tips. Leaves are glossy green on the top side, and whitish on the underside, hence the Malay name "Putih", which means "white". Salt glands on their undersides 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 in the shape of elongated inverted teardrops and are whitish/greyish green 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 of this plant is used as firewood and construction timber. The fruits are cooked and eaten, while resins from the seeds are used to treat skin diseases and wounds.
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