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Kaktüs, (Cactaceae familyası), çoğul kaktüsler veya kaktüsler, yaklaşık 2.000 tür ve 139 cins ile çiçekli bitki ailesi (Caryophyllales siparişi). Kaktüsler, Britanya Kolumbiyası ve Alberta'dan güneye doğru Kuzey ve Güney Amerika'nın çoğunda yer almaktadır; menzilinin en güney sınırı Şili ve Arjantin'e kadar uzanmaktadır. Meksika en fazla sayıda ve çeşide sahiptir. Eski Dünya'ya özgü olan tek kaktüsler, Doğu Afrika, Madagaskar ve Sri Lanka'da meydana gelen Rhipsalis cinsinin üyeleridir. Birkaç kaktüs türü tropikal veya subtropikal bölgelerde yaşıyor olsa da, çoğu kuru bölgelerde yaşar ve iyi adapte olur. Ayrıca bkz. Cactaceae familyasındaki bitkilerin listesi.
Caryophyllales: Kaktüsler
Kaktüsler meraklı, genellikle dikenli (dikenli), Cactaceae ailesini oluşturan etli köklü bitkilerdir, karakteristiktir ve iyi adapte edilmiştir
Fiziksel özellikler
Kaktüsler etli çok yıllık bitkilerdir. Kaktüsler genellikle kalın otsu veya odunsu klorofil içeren gövdelere sahiptir. Kaktüsler, diğer etli bitkilerden areoles, trikomlu küçük yastık benzeri yapılar (bitki kılları) ve neredeyse tüm türlerde dikenler veya dikenli kıllar (glochidler) ile ayırt edilebilir. Areoles, çiçeklerin, daha fazla dalın ve yaprakların (mevcut olduğunda) büyüyebileceği değiştirilmiş dallardır.
In most species, leaves are absent, greatly reduced, or modified as spines, minimizing the amount of surface area from which water can be lost, and the stem has taken over the photosynthetic functions of the plant. Only the tropical genera Pereskia and Pereskopsis, both vines, have conventional-looking functional leaves, while the leaves of the Andean Maihuenia are rounded, not flattened. The root systems are generally thin, fibrous, and shallow, ranging widely to absorb superficial moisture.
Cacti vary greatly in size and general appearance, from buttonlike peyote (Lophophora) and low clumps of prickly pear (Opuntia) and hedgehog cactus (Echinocereus) to the upright columns of barrel cacti (Ferocactus and Echinocactus) and the imposing saguaro (Carnegiea gigantea). Most cacti grow in the ground, but several tropical species—including leaf cactus (Epiphyllum), Rhipsalis, and Schlumbergera—are epiphytes, growing on other plants; others live on hard substrates such as rocks, while yet others climb far up trees. Epiphytic species tend to have thin, almost leaflike flattened stems. The appearance of the plant varies also according to whether the stem surface is smooth or ornamented with protruding tubercles, ridges, or grooves.
The primary method of reproduction is by seeds. Flowers, often large and colourful, are usually solitary. All genera have a floral tube, often with many petal-like structures, and other less colourful and almost leaflike structures; the tube grows above a one-chambered ovary. A style topped by many pollen-receptive stigmas also arises from the top of the ovary. The fruit is usually a berry and contains many seeds. Soon after pollination, which may be effected by wind, birds, insects, or bats, the entire floral tube detaches from the top of the ovary to leave a prominent scar.
Several cacti develop plantlets at ground level that, as offsets, reproduce the species vegetatively. Many others can reproduce by fragmentation, whereby segments broken from the main plant will readily root to form clonal individuals. Tissues of cacti are broadly compatible so that terminal portions of one species may be grafted on top of another.
The internal structure of cacti stems conforms to the pattern of broad-leaved angiosperms; a cambium layer of dividing cells, located between the woody inner tissues and those near the outside of the stem, is present. The bulk of the stem, however, consists of thin-walled storage cells that contain mucilaginous substances that prevent the loss of moisture. The stem of cacti is the main food-manufacturing and food-storage organ for most species.
Uses
Cacti are widely cultivated as ornamentals. In addition, various species, notably prickly pears and chollas (Opuntia and Cylindopuntia, respectively), are cultivated as food. In Central and South America, species of Opuntia, Cereus, and others are used as living fences, and wood from columnar cacti is used as fuel in some desert regions. In times of drought, the spines are removed from cacti such as mandacaru (Cereus jamacaru) to use as fodder for livestock. Peyote, from Lophophora williamsii, has been used ceremonially since pre-Columbian times for its hallucinogenic properties, and many cactus species are of local importance in traditional medicine.
