Plant Profile: White Mangrove, Laguncularia racemosa


By Kelsey Cooper, Rebecah Horowitz, and Katie Kara

Fig. 1. L. racemosa - pneumatocysts & paddle-
shaped leaves. Photo credit: T. Ann Williams.

This post is one of a series from professor Nisse Goldberg's Botany students at Jacksonville University.


Classification
Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Order: Myrtales
Family: Combretaceae
Genus: Laguncularia
Specific epithet: racemosa


Description
Laguncularia racemosa, or white mangrove, is a sprawling, woody shrub found in coastal habitats along West Africa, Northern South America, Mexico, the Caribbean Islands, and Florida. It can grow to be approximately 40 feet in height. In Florida, it is known to occur along the coast from Volusia County, around the southern tip of the state and northward on the Gulf side to Levy County. Laguncularia is a monotypic genus.

Figure 2. L. racemosa - flowers.
Photo credit: Glenn Fleming.
White mangroves' paddle-like leaves are oppositely arranged along the stem (figure 2). They have extra-floral nectaries -  glands at the leaf base that produce a sugary substance that wasps and ants like to eat. In turn, it is believed that these insects assist in protecting the plant from predation. Another interesting facet of white mangrove leaves is their ability to  "sweat" out salt.

Although it tends to occur close to saltwater, this is not because it requires salt, but because it tolerates salt - an attribute which gives it a competitive edge over many other plants. L. racemosa can survive periods of inundation in part because of structures called pneumatocysts (figure 1) which provide its roots with access to oxygen.

Figure 3. L. racemosa - fruits.
Photo credit: T. Ann Williams.
White mangrove produces relatively small white clusters of  flowers which blooms in the spring, (figure 2). Their petals are distinct, meaning they are not fused or connate. Small green fruits are produced from the flowers, with ridges running down the length of each fruit (Figure 3). The calyx that once made up the white flowers remains with the fruits. As with other mangrove species, the seeds remain on the mother plant during the period of seed maturation, detach, and then spend a required amount of time floating before they can establish.

The white mangrove is an important plant for numerous reasons. It serves as a windbreak along the coastline, its roots help slow erosion, and it provides birds, fish, and crustaceans with habitat for breeding, feeding, and nesting activities. Its wood is extremely durable and resistant to dry wood termites, but don't even consider cutting it down for this quality, as it is protected by the 1996 Mangrove Trimming and Preservation Act. Finally, its flowers are valuable to bees and apiculturists alike.

References

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