How Cacti Has Adapted

How Cacti Has Adapted

Amanda Wilkinson

BIO 101

March 24, 2012

Tomas Oberding

How Cacti Has Adapted

The barrel cactus has an extremely hot and dry environment to survive in. It is not the only cactus seen in the desert or even the most common, but it is a good example of how all cacti have had to adapt to survive in the most severe desert environment. (Waterworth, n.d.). From its barrel shape to its spines, each part of the barrel cactus has been formed from a long evolution in an unforgiving desert.

On the attached diagram, you will see the different parts of a cactus identified. I would like to start with discussing the areoles and tubercles. The areoles, a special auxiliary bud, are a special feature found on a cactus. It is distinct because no other plant family has it. Areoles have two growing points. One of the points produces the small hairs, also called glochids, you see on a cactus. The other point produces the spines that protect the cactus. ("Cactus and Succulent Society of New Zealand”, 2012). The tubercles, or round growths, sprout out of the cactus surface. In the case of the barrel cactus, the tubercles line up and form rows. (“Dictionary of Botanic Terminology”, n.d.). They expand with the ribs of the cactus increasing room for water storage during rainy seasons.

The spines, which can be found on all types of cacti, serve as a defense mechanism. Desert animals are less likely to try and eat the plant that is covered with prickly spines. In addition to being a defense mechanism, the spines also provide shade to the plant. The spines decrease evaporation by cutting off up to twenty percent of the harsh desert sunlight and raising the humidity in the shaded area found between spines. (“Tses Cactus of the Southwest”, 1997-2011)

The stem of a barrel cactus also helps it withstand the hot climate. The core of the stem itself is usually one to three inches around. It is covered in a wax-like substance that is very strong and tough. This...