cactus (plural: cacti, cactuses, or cactus) is any member of the succulent plant family Cactaceae, native to the Americas. They are often used as ornamental plants, but some are also crop plants.
Cacti are distinctive and unusual plants, which are adapted to extremely arid and hot environments, showing a wide range of anatomical and physiological features which conserve water. Their stems have expanded into green succulent structures containing the chlorophyll necessary for life and growth, while the leaves have become the spines for which cacti are so well known.
Cacti come in a wide range of shapes and sizes. The tallest is Pachycereus pringlei, with a maximum recorded height of 19.2 m,[1] and the smallest is Blossfeldia liliputiana, only about 1 cm diameter at maturity.[2] Cactus flowers are large, and like the spines and branches arise from areoles. Many cactus species are night blooming, as they are pollinated by nocturnal insects or small animals, principally moths and bats. Cacti's sizes range from small and round to pole-like and tall.
The cacti are succulent plants that grow either as trees, shrubs or in the form of ground cover. Most species grow on the ground, but there is also a whole range of epiphytic species. In most species, except for the sub-family of the Pereskioideae (see image), the leaves are greatly or entirely reduced. The flowers, mostly radially symmetrical and hermaphrodite, bloom either by day or by night, depending on species. Their shape varies from tube-like through bell-like to wheel-shaped, and their size from 0.2 to 15-30 meters. Most of them have numerous sepals (from 5 to 50 or more), and change form from outside to inside, from bracts to petals. They have stamens in great numbers (from 50 to 1,500, rarely fewer). Nearly all species of cacti have a bitter milk-like substance contained within them. The berry-like fruits may contain few, but mostly many (3,000), seeds, which can be between 0.4 and 12 mm long.[3]
The life of a cactus is seldom longer than 300 years, and there are cacti which live only 25 years (although these flower as early as their second year). The Saguaro cactus (Carnegiea gigantea) grows to a height of about 2ft tall on modern days in summer weather up to 15 meters (the record is 17 meters 67cm), but in its first ten years it grows only 10 centimeters. The "mother-in-law's cushion" (Echinocactus grusonii) reaches a height of 2.5 meters and a diameter of 1 meter and - at least on the Canaries - is already capable of flowering after 6 years. The diameter of cactus flowers ranges from 5 to 30 cm; the colors are often conspicuous and spectacular.
[edit] Distribution
Cacti are almost exclusively New World plants. This means that they are native only in North America, South America, and the West Indies. There is however one exception, Rhipsalis baccifera; this species has a pantropical distribution, occurring in the Old World tropical Africa, Madagascar and Sri Lanka as well as in tropical America. This plant is thought to be a relatively recent colonist in the Old World (within the last few thousand years), probably carried as seeds in the digestive tracts of migratory birds. Many other cacti have become naturalized to similar environments in other parts of the world after being introduced by people. The Tehuacán Valley of Mexico has one of the richest occurrences of cacti in the world.[4]
Cacti believed to have evolved in the last 30 to 40 million years. Long ago, the Americas were joined to the other continents, but separated due to continental drift. Unique species in the New World must have developed after the continents had moved apart. Significant distance between the continents was only achieved in around the last 50 million years. This may explain why cacti are so rare in Africa as the continents had already separated when cacti evolved. Many succulent plants in both the Old and New World bear a striking resemblance to cacti, and are often called "cactus" in common usage. This is, however, due to parallel evolution; none of these are closely related to the Cactaceae.
Prickly pears (genus Opuntia) were imported into Australia in the 19th century to be used as a natural agricultural fence and to establish a cochineal dye industry, but quickly became a widespread weed. This invasive species is inedible for local herbivores and has rendered 40,000 km² of farming land unproductive.
L.A
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one of those are soluti
chrissupra1 5 months ago
i don't want to fall in this pieces
karaekele 2 years ago
Je ne comprehends pas...
strawberryspatch 3 years ago