A cactus (pl.: cacti, cactuses, or less commonly, cactus) is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1,750 regarded species of the order Caryophyllales. The word cactus derives, by means of Latin, from the Ancient Greek word κάκτος (káktos), a identify originally made use of by Theophrastus for a spiny plant whose id is now not certain. Cacti come about in a large range of shapes and sizes. They are indigenous to the Americas, ranging from Patagonia in the south to components of western Canada in the north, with the exception of Rhipsalis baccifera, which is also uncovered in Africa and Sri Lanka. Cacti are adapted to dwell in very dry environments, like the Atacama Desert, a single of the driest places on Earth. Mainly because of this, cacti show quite a few diversifications to conserve h2o. For case in point, just about all cacti are succulents, indicating they have thickened, fleshy sections adapted to shop drinking water. Contrary to quite a few other succulents, the stem is the only part of most cacti in which this critical method will take place. Most species of cacti have missing accurate leaves, retaining only spines, which are remarkably modified leaves. As effectively as defending against herbivores, spines aid avert water decline by decreasing air stream shut to the cactus and giving some shade. In the absence of accurate leaves, cacti’s enlarged stems carry out photosynthesis.
Cactus spines are made from specialized buildings called areoles, a variety of highly reduced department. Areoles are an identifying characteristic of cacti. As perfectly as spines, areoles give increase to flowers, which are generally tubular and multipetaled. Quite a few cacti have short growing seasons and extensive dormancies and are capable to react immediately to any rainfall, aided by an extensive but comparatively shallow root procedure that promptly absorbs any water reaching the floor surface area. Cactus stems are normally ribbed or fluted with a quantity of ribs which corresponds to a selection in the Fibonacci numbers (2, 3, 5, 8, 13, 21, 34 etc.). This enables them to expand and agreement very easily for rapid drinking water absorption immediately after rain, followed by retention more than long drought periods. Like other succulent vegetation, most cacti employ a distinctive system identified as “crassulacean acid metabolism” (CAM) as component of photosynthesis. Transpiration, during which carbon dioxide enters the plant and water escapes, does not take spot all through the working day at the exact same time as photosynthesis, but alternatively happens at night time. The plant outlets the carbon dioxide it takes in as malic acid, retaining it till daylight returns, and only then applying it in photosynthesis. For the reason that transpiration requires put all through the cooler, much more humid night several hours, h2o reduction is significantly reduced.
Many scaled-down cacti have globe-formed stems, combining the optimum possible volume for water storage with the lowest achievable floor space for water loss from transpiration. The tallest free-standing cactus is Pachycereus pringlei, with a utmost recorded peak of 19.2 m (63 ft), and the smallest is Blossfeldia liliputiana, only about 1 cm (.4 in) in diameter at maturity. A thoroughly grown saguaro (Carnegiea gigantea) is explained to be ready to take in as significantly as 200 U.S. gallons (760 L 170 imp gal) of h2o all through a rainstorm. A few species vary significantly in visual appeal from most of the spouse and children. At the very least superficially, plants of the genera Leuenbergeria, Rhodocactus and Pereskia resemble other trees and shrubs expanding close to them. They have persistent leaves, and when more mature, bark-coated stems. Their areoles detect them as cacti, and in spite of their visual appeal, they, far too, have quite a few adaptations for water conservation. Leuenbergeria is thought of close to the ancestral species from which all cacti advanced. In tropical areas, other cacti increase as forest climbers and epiphytes (plants that improve on trees). Their stems are commonly flattened, almost leaf-like in visual appearance, with much less or even no spines, these kinds of as the effectively-regarded Christmas cactus or Thanksgiving cactus (in the genus Schlumbergera).
Cacti have a wide variety of makes use of: many species are utilized as decorative vegetation, other people are developed for fodder or forage, and others for food (specifically their fruit). Cochineal is the item of an insect that lives on some cacti.
