Thursday, May 10, 2012

Family Profile: The Lauraceae

By Lucas Hill

This post is one of a series from professor Nisse Goldberg's Plant Taxonomy students at Jacksonville University. FNPS blogger Laurie Sheldon assisted the students individually with their initial drafts, and provided them with editorial feedback and guidance for content development.

Characteristics
Leaf: simple, entire, alternate (leaves on opposite sides of the stem and do not attach at the same point), and spiral (rotating in position along the stem)
Flower: bisexual or unisexual, radial, usually small and pale 
Fruit: berry-like drupe

Description
Members of the family Lauraceae are mostly trees and shrubs, with one genus (Cassytha) that is a parasitic vine. Many are rich in aromatic ethereal oils that have terpenoids and alkaloids (organic chemicals that have many uses to the plant, including defense). This family consists of 50 genera, 8 of which are found here in Florida. The red bay (Persea borbonia var. borbonia, Fig. 1), silk bay (P. borbonia var. humilis, Fig. 2), and swamp bay (P. palustris, Fig. 3) are native to Florida. The leaves of red bay are white on their lower surface as compared to the lower surface of the silk bay leaves, which are a rusty or copper color. Both varieties of P. borbonia have small hairs on the lower surface of the leaves, giving them a silky texture, while P. palustris has relatively larger hairs on its leaves. Red bay has been devastated in recent years by a fungal infection called laurel wilt (Raffaelea lauricola) which is carried by the ambrosia beetle (Xyleborus glabratus). This disease affects the vascular system of the plant, which transports nutrients and water throughout the plant.

Other well-known species of this family in our region are the native sassafras tree (Sassafras albidum, Fig. 4), the avocado (Persea americana), and the non-native camphor tree (Cinnamomum camphora). Sassafras is unique in that it can bear three different shapes of leaves on the same tree, a condition known as heterophylly. Other more rare species of Lauraceae in our area include those of the genera Cassytha and Lindera (spicebush).

Fun Facts 
Many members of this family are used as spice plants,
   including Laurus nobilis (bay leaves), Cinnamomum
   verum (cinnamon), C. camphora, and S. albidium. 
The leaves of Laurus nobilis, the bay laurel, were formed
   into crowns by the ancient Greeks.
Members of the genus Pleurothyrium have a symbiotic
   relationship with ants that protect the tree.

References
Judd, WS, Campbell, SC, Kellogg, EA, Stevens, PF, and Donoghue, ML. 2008. Plant systematics: A
     phylogenetic approach. Sinauer Associates, Inc. Massachusetts, USA.
Wunderlin, RP and Hansen, BF. 1998. Guide to the Vascular Plants of Florida. Gainesville: University
     of Florida.
USDA Forest Health Protection. "Laurel Wilt." US Forest Service. USDA Forest Service - Forest Health
     Protection, Southern Region, 04 Mar. 2012. Web. 06 Apr. 2012.

Image Sources
Figure 1. http://aquilegia.uchicago.edu/naturalsystems/class/plantsystematics/photos/0102.jpg
Figure 2. http://florida.plantatlas.usf.edu/Photo.aspx?id=14552
Figure 3. http://herbarium.biol.sc.edu/herb/PP/Persea_palustris1.jpg
Figure 4. http://aquilegia.uchicago.edu/naturalsystems/class/plantsystematics/photos/0104.jpg

No comments: