use ultrafiltration at the root level to exclude salt. It is believed that
they store any salt that gets through in old leaves which they later shed.
Rhizophora grow best in wet, muddy and silty sediments.
Rhizophora species have arching stilt roots that emerge from
the trunk, hence their scientific name Rhizophora which means
"root bearer" in Greek.
These roots not only hold up the tree in soft mud, but are also permeable
to gases, while remaining impermeable to salts. In fact, the entire
upper root system including the trunk and prop roots that emerge from
the branches have this feature. Thus the roots also help the tree
and wetland wildlife at
Sungei Buloh Nature Park
features: Grows 15-25m tall.
Roots: Stilt roots emerging
in arches from the lower trunk, and prop roots may grow
downwards from branches.
Leaves: Tiny black spots
on the underside of the leaf.
Flowers: Flower inflorescence long, slender and
yellow. No scent or fragrance, wind-pollinated.
Fruits: The seed germinates
in the fruit forming a seedling.
World distribution: East
Africa through coasts of the Indian Ocean to Southeast
Asia, China, Australia, Melanesia, Micronesia.
Classification: Family Rhizophoraceae.
World 8 mangrove species.
tiny flowers are wind-pollinated, producing lots of powdery pollen
and no fragrance or nectar. They are also self-pollinating.
fruit does not fall away when it ripens. Instead, the single seed
within the fruit starts to germinate while it is still on the mother
tree, and the mother tree channels nutrients to the growing seedling
(vivipary). The seedling forms a stem (called a hypocotyl).
When the seedling finally falls, at first it floats horizontally,
and drifts with the tide. It can survive for long periods at sea.
After some weeks, the tip gradually absorbs water and the seedling
floats vertically and starts to sprout its first leaf from the top,
and roots from the bottom. When it hits land, it grows more roots
to anchor itself upright, and then more leaves. Rhizophora
seedlings grow rapidly to avoid being submerged at high tide. They
can grow by 60cm in the first year.
Because Rhizophora are fast growing and flower within their
first year, they are often used to replant mangroves either for conservation
or as part of a managed forest to produce timber for construction
or charcoal. The other mangrove species used in replanting mangroves
are Avicennia and Sonneratia.
Sungei Buloh Nature Park
Minyak (R. apiculata): leaf stipule and leaf
stalk reddish. Flower inflorescence short, stout, dark grey.
Seedlings shorter (30cm), slender with a smooth skin and grows
slightly curved with a rounded tip. More restricted distribution,
only Southeast Asia and Micronesia.
Bakau (R. stylosa)
Bakau Kurap (R. mucronata):
In both, the flower inflorescence is longer, slender and yellow,
the seedling is longer (60cm) and has a warty bumpy surface.
The flower of R. stylosa: has a longer style (4-6mm).
R. mucronata is more widespread and also found in East
Africa where R. stylosa is not found.
Role in the habitat: see mangrove
Status and threats: R. stylosa
is listed among the endangered plants in Singapore, but it is common elsewhere.
- Peter K L Ng and
N Sivasothi, "A Guide to the Mangroves of Singapore I: The Ecosystem
and Plant Diversity", Singapore Science Centre, 1999 (p. 126-133:
description, habit, photo.
- Michael Mastaller,
"Mangroves: The Forgotten Forest Between Land and Sea",
Tropical Press, 1997 (p. 28-30: about the roots; p. 34-35: about how
seedlings disperse and sprout; p. 97: medicinal uses).