The geographical distribution of Laguncularia racemosa covers both coasts of tropical America, the Caribbean and tropical west Africa.
Biology of the White Mangrove
The white mangrove is a tall evergreen tree; it grows to heights of 80 feet and frequently has multiple trunks growing from a root system.
The white mangrove prefers moist soil rather than the partly submerged soil that its relatives, the red mangrove and black mangrove, like. David Nellis states, in the 1994 edition of Seashore Plants of South Florida and the Caribbean, that if the salinity of the soil starts to exceed that of seawater then the white mangrove’s growth will decrease and often the black mangrove will move in and replace the habitat.
The white mangrove has a shallow horizontal root system, and in order to obtain oxygen from the saturated soils it inhabits it will send up ‘snorkels’ to allow the roots to breathe. These snorkels are referred to as pneumatophores and are an adaptation of the black mangrove to waterlogged soils. Laguncularia racemosa copes with high salinity soils by excreting salt through its leaves. The leaves of the white mangrove are leathery and have red petioles near the leaf base. These petioles have 2 glands that excrete the salt from the white mangrove and salt crystals cover the leaf underside. This could be the reason for the common name white mangrove, that the leaves appear white from the salt crystals, although the upper trunk and branches of Laguncularia racemosa are often white in colour too.
The white mangrove blooms delicate white flowers in the spring and early summer. The propagules of Laguncularia racemosa are pea shaped and green. The white mangrove is viviparous; it produces a ‘live’ seed that continues to grow whilst attached to the parent plant, rather than the dormant seeds that most plants produce. The propagule of the white mangrove must float for 5 days in the water once it has dropped from the parent tree before it is ready to put down roots. During this 5 day dispersal period germination takes place in the propagule so the white mangrove is actually referred to as semi-viviparous, unlike its relatives the red and black mangrove whose propagule germinate whilst still attached to their parent and are therefore fully viviparous.
Ecological Importance Of The White Mangrove
The white mangrove like other members of the mangrove ecosystem contributes significantly to reduce coastal erosion as a result of storms. The vest, dense root system, found more inland than root systems of the red and black mangrove, helps to reduce the amount of sediment that will be washed off the land in to the sea with water runoff after a storm.
Physical Uses Of The White Mangrove
The wood of Laguncularia racemosa is hard and strong; it has been used for house frames and also fuel. The bark and leaves contain high levels of tannins; the bark contains 10% and the leaves 17%, as cited in Seashore Plants of South Florida and the Caribbean resulting in their use in the tanning and dyeing industry.
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