wetlands
a publication of Sungei Buloh Nature Park
Vol 8 No 1
Apr 2001

Breathing organs
in mangroves

Bird watching techniques

A place in space:
epiphytes

Bird ringing
in 2000

Gems of the park: volunteers

Our long
suffering
"mother"

Public talks
at the park

Reflections
of a nature warden 		 
breathing organs
in mangroves
by ali ibrahim
conservation officer
The mangal substratum consisting of dense mud is rather anaerobic (lacking in oxygen) and unstable. The mangrove plants, commonly found in the Park, have invariably adapted to this exacting environment by having lenticels (respiratory pores) and numerous passages through their spongy tissues to allow air to enter the roots below.

Roots that are exposed to the atmosphere, at least during low tide, may be called aerial roots.

Surface roots
These rooting adaptations include stilt roots, various type of pneumatophores and aerial roots. Not all mangrove species possess a specialised root system while some species possess more than one of the mentioned adaptations.

Pneumatophores (erect, asparagus-, peg- or torpedo-shaped) are respiratory roots belonging to Avicennia sp., Sonneratia sp. and Xylocarpus moluccensis. In the former species, the roots are pencil-like arising upright from massive subterranean cable roots system into the outer environment. When not inundated these roots are able to breathe. The pneumatophores produce an extensive net of fine nutrition roots that can also assimilate oxygen from the uppermost mud layer. A close examination at the pneumatophores will reveal the presence of barnacles, molluscs and algae on its exterior. A myriad of crustaceans, mudskippers and fishes also treat the site as feeding or play-ground.

knee roots
 Knee roots in Bruguiera sp., Ceriops tagal and Lumnitzera littorea provide air to its root system via a system of quaint, knoblike structures. These lenticillated pneumatophores being periodically exposed to the air facilitate gas exchange between the atmosphere and the internal tissues of the plant.

Stilt roots in Rhizophora sp., with water-accustomed arching appendages arising from the trunk and lower branches, besides aiding in aeration serve also to anchor the tree in the soft and unstable mud. Birds and tree-climbing crabs even use the trunk and extended arms of Rhizophora to perch.

Prop roots in Rhizophora sp., Avicennia sp. and Acanthus ilicifolius are unbranched adventitious roots growing downwards from branches or the canopy to the bottom. Unlike stilt roots, these aerial roots are of uniform thickness and flexibility and will not root on reaching the ground. They, however, lend support to the tree.

Surface roots occur in Excoecaria agallocha, Aegicceras corniculatum and Cebera sp. The network of spreading surface roots is able to absorb sufficient oxygen during low tidal exposures.

Finally, plank roots, which are thin, branched, ribbon-like buttresses spreading out from the base of its trunk also aid in the aeration of Xylocarpus granatum and Heritiera littoralis.

It is therefore imperative for the survival of mangroves that oil pollution on a large scale must not occur, as breathing roots when coated will suffer from dire physiological consequences. For to err is human, to breathe... simply divine!

Do look out for these mangrove plants on your next visit to the Park. You would he amazed at the intricate structure and inherent beauty of these "breathing roots".
   
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