Gedabu (Sonneratia ovata)

The Gedabu (Sonneratia ovata) 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 occurs at the landward margin of mangroves in less saline areas, usually on muddy soils and along tidal creeks. In Singapore, naturally occurring ones can be found at Sungei Buloh Wetland Reserve, Kranji Nature Trail, Mandai Mangrove, Khatib Bongsu, Pulau Ubin and Pulau Tekong, among others.


The trunk is cream-coloured to 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. ovata relies on its roots to exclude salt from entering the plant through a process called ultrafiltration.


It has simple, opposite leaves that are broadly ovate, oval or almost round.


The mature flower buds reveal the white stamens and long style about a day before it finally blooms.


The flowers bloom at night, revealing numerous stamens which are shed the next morning. Petals are absent, and the filaments are all white. The sepals are reddish on the inside and green on the outside. The flowers are pollinated by nectar-feeding bats and moths at night, and birds in the morning.


The fruits are round, with the calyx enveloping the berry.


Each fruit contains numerous seeds which has air-bearing tissues, allowing them to float and be dispersed by water.

The wood is used for firewood, and the fruit is eaten by locals, and hence the tree is often cultivated in Malay villages.

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.