Bakau Pasir is a mangrove tree with prop roots. Leaves are opposite, oblong-elliptic, with cork warts (black dots) below. Stipules yellowish green. Flowers 2-14 in a forking inflorescence on a long, slender yellow stalk. Seeds viviparous. Hypocotyl warty, with pointed tip and can grow to 60 cm long. Size: 8-20 m tall.
Rhizophora spp. are easily identified by their characteristic prop or stilt roots which help to increase the stability of the plant's anchorage in the unstable mangrove mud, as well as for aeration of the root tissues.
Rhizophora is well adapted to live in the marine environment. It is able to exclude salt by an ultra-filter in the roots, where water is taken up and salt is largely excluded from entering the plant.
It prefers sandy substrates.
The fruit of Rhizophora contains seeds which develop precociously, that is, the seed germinates while still attached to the parent tree. The embryo develops into a seedling (propagule) without a dormancy period; the seedling root (radicle) breaks through the fruit wall and grows beyond it, while still attached to the parent tree. This condition is termed as vivipary.
The seedling is dispersed by sea water, floating horizontally at the initial stage. After a few weeks when it absorbs more water and becomes heavier, it will then float vertically.
The floating seedling will be planted vertically into the soft mud when the tide recedes, away from the parent tree.
Very tolerant of salinity changes and is the most important plant for reforestation, allowing other species to colonise once it has established itself.
Rhizophora apiculata and Rhizophora mucronata.
Bakau timber has a high calorific value, so it makes excellent firewood or charcoal. The bark tannin is used as a dye, for toughening fishing lines and tanning. Bakau wood is straight, strong and extremely resistant to insects and rot, even when submerged in seawater. Hence it is also used in construction sites and in kelongs.