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CACTACEAE
FAMILY
Cactus
Family | Cactus
Types | Opuntia
- All but one cactus species is endemic to (occurs naturally only in) the New World
- All cacti are succulent (have water-storing tissue), but not all succulents are cacti (e.g., Sotol). This sometimes makes it difficult to distinguish cacti from other plants that convergently evolved (developed similar characteristics due to experiencing similar environmental constraints) with cacti (e.g., Ocotillo).
- To be
a cactus, the plant must have the following set of characteristics:
- areoles: structures from which spines, branches, and flowers come (see picture).
- flowers with many sepals and petals that intergrade with each other.
- flowers with many stamens.
- flowers with multi-lobed stigma.
- Most cacti use CAM (Crassulacean Acid Metabolism) photosynthesis, taking in carbon dioxide at night instead of the day to save water (evaporation rates are lower at night generally), storing the carbon dioxide as an acid, and then releasing the carbon dioxide during the day for photosynthesis.
- Columnar cacti, with leguminous trees, characterize the Sonoran Desert
- Besides columnar cacti, other major groups include barrels, hedgehogs, pincushions, chollas, and prickly pears (see Major Types of Cacti).