|Figure 1: Opuntia corallicola, semaphore pricklypear.|
Photo credit: T. Ann Williams.
Leaves: typically reduced as spines
Flower: zygomorphic or actinomorphic, with tepals rather than sepals and petals
|Figure 2: The specific epithet of Harrisia fragrans may|
allude to its sweet smelling flowers.
Photo credit: Keith Bradley.
The cactus plant family or Cactaceae is specially adapted to survive in hot and dry conditions. For example, many species have sharp spines to protect them from predation, direct rain runoff towards their root system, and reduce internal heat loading by reflecting light away from the plant (Fig. 1). In addition, the dermal cells are thick-walled and lined with a cuticle or waxy layer. The cuticle helps the plant retain water and to reflect light, thereby reducing internal temperatures.
|Figure 3: Lophophora williamsii has no spines .|
Photo credit: Kauderwelsch
The root system of the cactus remains relatively close to the surface while extending out up to 15 meters! During heavy amounts of precipitation, the roots will begin to grow new root extending from the previous roots to increase water absorption. During times of drought the roots will begin to shrivel and deteriorate creating an air gap that can help trap water.
There are 23 species of Cactaceae in Florida, 12 of which are native. Among the native species, 7 are listed by the state as endangered. Examples of these include Opuntia corrallicola, semaphore pricklypear, and Harrisia fragrans, Caribbean applecactus (Figs. 1 and 2). Found in Texas, Peyote or Lophophora williamsii is known for psychoactive effects (Fig. 3).
Judd, WS, Campbell, SC, Kellogg, EA, Stevens, PF, and Donoghue, ML. 2008. Plant systematics: A phylogenetic approach. Sinauer Associates, Inc. Massachusetts, USA
Figure 1: http://www.florida.plantatlas.usf.edu/plantimage/Opuntia_corallicola2.jpg
Figure 2: http://www.florida.plantatlas.usf.edu/plantimage/Harrisia_fragrans6.jpg
Figure 3: http://upload.wikimedia.org/wikipedia/commons/thumb/3/3e/Lophophorawilliamsii.jpg/320px-Lophophorawilliamsii.jpg