Berembang (Sonneratia caseolaris)

The Berembang (Sonneratia caseolaris) is a nationally critically endangered mangrove tree from the family Lythraceae. As with the other Sonneratia species it is also commonly called "Mangrove Apple".


It usually occurs at the less saline parts of mangrove forests on muddy substrates, especially those with freshwater inputs (e.g. banks of tidal rivers). In Singapore, I have seen naturally occurring trees at Woodlands Town Garden, Sungei Buloh Wetland Reserve, Kranji Nature Trail, Berlayar Creek, Pulau Ubin and Pulau Tekong.


The trunk is brown. Cable roots radiating from the tree underground arise at various intervals to form conical pneumatophores. These roots help the plant breathe air, which is scarce in the waterlogged soil. The roots spread over a wide area to help stabilise the tree on the unstable ground. Like other Sonneratia species, S. caseolaris relies on its roots to exclude salt from entering the plant through a process called ultrafiltration.


It has simple, opposite leaves with pointed tips. A minute, recurved point occurs at the tip. Young branches hang down like those of the weeping willow. During heavy rains the inclination of the leaves may shift from horizontal to vertical.


Flower bud that is about to open may have pinkish to dark red stamens. The sepals of the flower are green outside and yellow inside (see previous photo).


The flowers usually bloom at night, revealing numerous stamens which are shed the next morning. The filaments are either all white, or white in the upper part and red in the lower part. The petals are red. They are pollinated by nectar-feeding bats and moths at night, and birds in the morning.


The fruit is persimmon-like with a flattened calyx tube. The sepals extend horizontally from the stalk or bend down towards the fruit. Each fruit contains numerous seeds which has air-bearing tissues, allowing them to float and be dispersed by water.

The fruits are eaten by locals, while the fruit juice is used to treat cough and pmixed with other herbs for treating blood in the urine. The pneumatophores are used to make corks and floats.

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.
• 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. & N. Sivasothi. 1999. A guide to the mangroves of Singapore 1 : the ecosystem & plant diversity. Singapore Science Centre. Singapore. 168 pp.