Like other succulents, these cacti have a range of specific adaptations that enable them to survive in these environments.
Cacti have become popular as indoor houseplants, including various South American tree-growing species with large, long-lasting flowers.
Like other succulents in the families of the Crassulaceae, Agavaceae (agaves), Euphorbiaceae (euphorbias), Liliaceae (lilies), Orchidaceae (orchids), and Vitaceae (some vines), cacti reduce water loss through transpiration by a process called crassulacean acid metabolism.
The cochineal dye is a rich red dye which is produced by the female cochineal insect, which lives on cacti.
Hummingbirds would have a difficult time migrating over the southwestern desert between their winter and summer ranges without cacti flowers as a source of food.
One feature distinguishes the cacti from all other plants: cacti possess areoles, as they are known.
Cacti are distinctive and unusual plants, with 2,000 to 3,000 species.
which are known as orchid cacti and Christmas cacti (Patriquin 2007, de Cameron 2007).
Most cacti have a short growing season and long dormancy, adapted to the rare availability of water.
The larger columnar cacti also develop a taproot, primarily for anchoring but also to reach deeper water supplies and mineral nutrients (Patriquin 2007).
Many species of cacti are endangered because of this as well as other threats to their environments.
Many other cacti have become naturalized to similar environments in other parts of the world after being introduced by humans.
Cacti play an important role in the desert ecology and are a vital source of food and water for many desert animals.
Some cacti grow on the branches of trees.
Cacti leaves typically are reduced in the size so that they reduce the surface area through which water can be lost by transpiration.
Cacti inhabit the most diverse regions, from coastal plains to high mountain areas, from the sub-tropics to the deserts.
Much like many other plants that have waxy coatings on their leaves, cacti often have a waxy coating on their stems to prevent water loss.
Interest in cacti has spread around the world since the discovery of the New World by Europeans.
Humans have long used cacti for food and other uses.
Most cacti are self-incompatible, and thus require a pollinator.
Some cacti also have enlarged roots, as does the sweet potato, for storage of water and carbohydrates (Mauseth 2007).
The equivalent plants to cacti in Africa and Australia are representatives of the so-called "other succulents."
Cacti come in a wide range of shapes and sizes.
The most dense occurrence of cacti is to be found in the territories around north Mexico and the southern tropic (Argentina and Bolivia).
The smallest cacti grow almost completely underground or in the cracks between rocks.
Other cacti are also used for traditional medicinal purposes and are the subject of modern pharmacological research.
Cacti play very important roles in their environments.
The prickly pear (Opuntia stricta) is one of the most widely cultivated cacti.
All cacti are covered by the Convention on International Trade in Endangered Species of Wild Fauna and Flora, and many species by virtue of their inclusion in Appendix 1 are fully protected (Marinelli 2005).
Because regular leaves don't conserve water well, the cactus developed these modified leaves to adapt to its extremely dry environment. The spines are better at conserving water and surviving in hot temperatures. Regular leaves provide a large surface area for evaporation of water to occur, the tiny spines do not.