Quest for the Trogon
Chapter 7. Plants
Cactus are one of the most distinctive families (Cactaceae) of plants. Few plants can be confused with cactus. Cactus have large, leafless, fleshy stems of different shapes and sizes that are studded with distinctive clusters of spines. The family is found only in the western hemisphere, with one exception, an epiphytic species that has dispersed to Africa, Madagascar, and Sri Lanka with the help of globe trotting birds. Otherwise, cacti range from western Canada to Patagonia. The first Europeans to see cactus were undoubtedly Christopher Columbus and his crew men. Unfortunately, they did not report any observations of the unusual plants.
Cacti have a wide range of shapes and sizes, and most live in habitats that have periodic droughts. Cactus have adapted to extreme aridity, and some inhabit the Atacama Desert, one of the driest places on earth. These plants are masters of adaptations to conserve water. Their fleshy stems store water and carry out photosynthesis. True leaves have been lost in most cacti although the spines are considered modified leaves.
Spines (or glochidia) are the primary defense against herbivores, but they also reduce water loss by interrupting air flow over the surface of the stem and providing some shade for the stem. Spines grow from specialized areoles, a highly modified branch. The areoles also give rise to flowers, which are usually tubular and have multiple petals. The spines can be a deterrent not only to herbivores but to naturalists. They may be bristles, hairs, or hooks in a variety of shapes and be curved, long, short, or straight. Removing glochidia may be difficult, pulling them out may fracture the spines and embed a portion of it into the skin.
Cactus stems are often ribbed or fluted, for rapid expansion when water is available and for contraction after a prolonged drought. The root system is shallow and dispersed around the plant for quick water absorption. A fully grown Saguaro, Carnegiea gigantean, may absorb as much as 200 U.S. gallons (760 liters) of water during a rainstorm. Cacti are CAM (crassulacean acid metabolism) plants. A specialized chemical pathway in photosynthesis that takes place at night and allows carbon dioxide to enter the plant while water is Cactus are one of the most distinctive families (Cactaceae) of plants. Few plants can be confused with cactus. Cactus have large, leafless, fleshy stems of different shapes and sizes that are studded with distinctive clusters of spines. The family is found only in the western hemisphere, with one exception, an epiphytic species that has dispersed to Africa, Madagascar, and Sri Lanka with the help of glob trotting birds. Otherwise, cacti range from western Canada to Patagonia. The first Europeans to see cactus were undoubtedly Christopher Columbus and his crew men. Unfortunately, that did not report any observations of the unusual plants.
Cacti have a wide range of shapes and sizes, and most live in habitats that have periodic droughts. Cactus have adapted to extreme aridity, and some inhabit the Atacama Desert, one of the driest places on earth. These plants are masters of adaptations to conserve water. Their fleshy stems store water and carry out photosynthesis. True leaves have been lost in most cacti although the spines are considered modified leaves.
Spines (or glochidia) are the primary defense against herbivores, but they also reduce water loss by interrupting air flow over the surface of the stem and providing some shade for the stem. Spines grow from specialized areoles, a highly modified branch. The areoles also give rise to flowers, which are usually tubular and have multiple petals. The spines can be a deterrent not only to herbivores but to naturalists. They may be bristles, hairs, or hooks in a variety of shapes and be curved, long, short, or straight. Removing glochidia may be difficult, pulling them out may fracture the spines and embed a portion of it into the skin.
Cactus stems are often ribbed or fluted, for rapid expansion when water is available and for contraction after a prolonged drought. The root system is shallow and dispersed around the plant for quick water absorption. A fully grown Saguaro, Carnegiea gigantean, may absorb as much as 200 U.S. gallons (760 liters) of water during a rainstorm. Cacti are CAM (crassulacean acid metabolism) plants. A specialized chemical pathway in photosynthesis that takes place at night and allows carbon dioxide to enter the plant while water can not escape. The globe-shaped stems of many cacti evolved for retaining the highest ossible volume for water storage while keeping the lowest possible surface area for water loss from transpiration.
Cacti range in size from the giant, 19-meter Pachycereus pringlei from northwestern Mexico to the small, one-centimeter Blossfeldia liliputiana from Argentina and southern Bolivia. Many succulent plants in the Old and New World, such as some Euphorbiaceae (euphorbias), are strikingly similar to cacti, and may incorrectly be called cactus.