Cactaceae

Cactaceae is a family of flowering plants in the order Caryophyllales, native to the Americas. It comprises about 127 genera and more than 1,800 species. Cacti are well adapted to arid and semi-arid environments and are known for succulent stems and specialized areoles from which spines and flowers arise.

Morphology and physiology: Areoles are unique to cacti and give rise to spines, flowers, and new shoots. Most cacti store water in stems and have reduced or absent leaves. Many use Crassulacean acid metabolism (CAM), opening stomata at night to conserve water. Forms range from globular to columnar to flattened pads (Opuntioideae). Spines, hairs, and glochids vary by lineage.

Reproduction and ecology: Flowers are often large and showy, pollinated by bees, birds, or bats. Fruits are frequently fleshy and may be edible. Seeds are dispersed by animals. Cacti inhabit deserts, dry shrublands, and some montane regions from Patagonia to northern Mexico; some species extend into tropical dry forests or cloud zones.

Taxonomy and notable genera: Major groups include Opuntia (prickly pears), Ferocactus, Echinocactus, Mammillaria, Cereus, and Carnegiea (including the saguaro). Classification has shifted with molecular data, and species boundaries are continually revised.

Uses and conservation: Cacti are widely cultivated as ornamentals and for arid-land landscaping. Edible fruits and pads of Opuntia are used in cuisine in various cultures. Some species face threats from habitat loss, overcollection, and climate change, and many are protected by regional conservation laws.