por The cacti (Cactaceae) commonly known as cacti, are a taxonomic family of succulent and spiny plants belonging to the order Caryophyllales. Native to America, they are widely distributed throughout the continent, from southern Argentina and Chile to northern Canada.
These plants constitute a very diverse group of approximately 1,900 species distributed among the more than 125 described genera. In fact, they are located mainly in arid and semi-arid ecosystems at altitudinal levels from sea level to 4,000 meters above sea level.
The cacti are characterized by their fleshy consistency, the presence of thorns and large solitary flowers and bright colors. There is a great diversity of shapes and sizes, cultivated as ornamental, for industrial use and for human or animal consumption.
The presence of certain morphological and physiological characteristics make these plants excellent colonizers of hot and arid environments. Indeed, they have succulent stems to store water and leaves modified into thorns that, in addition to protection, favor direct reflection of solar radiation.
In addition, they have developed the CAM metabolism «crassulacean acid metabolism» that regulates the photosynthetic process and photorespiration. In this way they prevent the opening of the stomata during the day, reducing the loss of water through transpiration.
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General characteristics
Habit
Cacti are herbaceous or shrubby, climbing or epiphytic, perennial and succulent plants with a cylindrical, globose or columnar appearance. Frequently they present thorns and areoles, in addition the bushy species are erect or often creeping.
Root
Tuberous roots are generally highly specialized to favor the storage and conservation of water or nutrients. On the other hand, in some species adventitious, epiphytic or climbing roots are deployed that facilitate the support of the plant.
Stem
The thick and succulent stem of the cacti essentially constitutes the body of the plant, being green in color due to its photosynthetic capacity. They can be simple or branched, with a smooth surface, tuberculate or divided into ribs, with segments in cylindrical or flattened segments.
Areola
The areoles are characteristic vegetative structures of cacti, similar to the buds present in stems and branches of dicotyledons. They are organs with a woolly appearance where branches, spines, bristles, glochids or «thin leaf spines», fluff, flowers or fruits emerge.
Leaves
The typical leaves are absent in the cacti, since in most of these species they have been modified into spines. Indeed, both structures develop from the same vegetative points and present a similar phylogenetic development.
The spines are arranged in the form of fascicles on each areole or pads similar to the vegetative buds. These structures present two points of meristematic development, where thorns, buds or flowers alternately originate.
Flowers
The flowers appear solitary and rarely grouped; they are hermaphroditic or unisexual; most are actinomorphic, although some are zygomorphic; frequently, fleeting nocturnal or diurnal.; sessile or pedunculated; composed of numerous external tepals with a sepaloid appearance, showy, scented, white, yellow, orange, pink, red or purple.
fruits
The fruits are generally fleshy, baciform in appearance, dehiscent or indehiscent. In some genera they are hollow and appear dry when ripe. They are made up of a fleshy pericarp with juicy pulp, with the surface covered with bristles, spines, glochids, scales or tubercles.
Seeds
The small, irregularly shaped seeds are ovoid, circular, elliptical, or oblong. They regularly measure between 0.5-100 mm in diameter, lack endosperm and sometimes have perisperm.
taxonomy
– Kingdom: Plantae
– Division: Magnoliophyta
– Class: Magnoliopsida
– Order: Caryophyllales
– Family: Cactaceae Juss., 1789
Etymology
The name «cactus» comes from the Greek «Κάκτος káktos», initially used by the philosopher Theophrastus to identify a type of thorny thistle. This thistle located on the island of Sicily, possibly it is the thistle Cynara cardunculus.
This expression later passed into Latin as «carduss», which finally derived in the Spanish word «cardo». In the end, the word «cactus» was used by Carlos Lineo to designate a genus that grouped 22 species belonging to the Cactaceae family.
Habitat and distribution
Cacti are succulent plants that are found in desert environments and arid ecosystems, likewise they inhabit in an epiphytic way in tropical forests. Native to tropical, subtropical, and temperate regions of the American continent, from Canada to Patagonia, and from the Galapagos to Fernando de Noronha Island.
They are located scattered in various ecosystems, predominantly arid environments, mountains and mountains, from sea level to 4,500 meters above sea level in the Andes. Most are semi-desert species adapted to hot American conditions, feral in regions such as Madagascar, Ceylon, and Sri Lanka.
The ideal habitat of most cacti is governed by occasional rains with intervening periods of prolonged drought. However, abundant morning dew is required when the average values of day and night temperatures decrease.
Its geographical distribution is located mainly in South America and North America. In Africa the genus is distributed only rhipsalis. The greatest diversity occurs in the Mexican desert, the southeastern US, the central Andes region, and southeastern South America.
Spread
Cetaceans can be commercially reproduced sexually by seed, or vegetatively through cuttings and grafting. Indeed, each method has its advantages and disadvantages, but the success of its propagation depends on handling during the process.
Seed
Through seed propagation, plants with the genetic characteristics from both parents are obtained. This is a slow process used to propagate hybrids or varieties, to obtain virus-free plants with genotypic diversity.
Sowing is done in early spring from seeds of known origin, free of pests or diseases and with a high degree of viability. In addition, it is necessary to maintain environmental conditions: temperatures between 20-30 ºC for most species and constant humidity during the germination process.
On the other hand, due to the small size of the seeds, a light substrate must be selected and the seeds placed at a superficial level. Depending on the environmental conditions and the availability of humidity, the germination of the seeds begins after 10-20 days.
During the germination phase, the aeration of the seedlings should be facilitated and the direct incidence of sunlight should be avoided. If it is required to speed up the process, a greenhouse can be used, where it is easier to control the different factors that influence germination.
cuttings
The use of cuttings is a vegetative propagation technique that allows obtaining a greater number of plants in the shortest possible time. In fact, the new plants have the same genotypic characteristics of the mother plant, although they may differ phenotypically from the plants obtained from seeds.
The best time to multiply by cuttings is during spring or summer, or under cool weather conditions. The cuttings are obtained directly from the plant by means of a clean cut, using sharp and disinfected tools.
It is convenient to let the cut place heal, keeping it in a ventilated and illuminated place, where direct sunlight falls. After 12-18 days, once the wound has healed, sow on a moist substrate.
A loamy-sandy type substrate is recommended that favors drainage, but maintains humidity. While the cutting develops the roots, moderate watering is recommended to avoid waterlogging and facilitate the development of the new plant.
Graft
Cactus grafting is done in order to multiply a new variety and obtain plants with flowers of different colors. At the time of grafting, it must be verified that the two varieties or species used are compatible.
The pattern or rootstock must come from a vigorous plant adapted to the environmental conditions where the crop will take place. In fact, it must be free of common pests or diseases in its environment and have similar physiological conditions to the species to be grafted.
When selecting the plants, it is convenient that both are of the same botanical genus or that they are very close species. Likewise, they agree that the rootstock is a young plant, less than three years old, that is conditioned for the process.
The best time to graft is during spring or summer, when the plants are in full vegetative period. Once the graft is done, the plant must maintain constant humidity conditions and be protected from direct solar radiation.
Crop
Substratum
The cacti are species adapted to hot and dry climates, that is, they adapt to xerophytic or drought conditions. However, like all living beings, they need water to survive, so their cultivation requires a substrate that retains moisture.
It is recommended to use a substrate, porous, loose, loamy-clay, with good drainage and an average pH of 6-7. It is essential that the substrate does not become flooded, since it can cause the appearance of fungal diseases at the root level.
Irrigation
Cacti are plants adapted to dry conditions, so the conditions of their natural environment must be taken into account. In fact, cacti tolerate a lack of humidity very well, but they are very sensitive to excess water.
Generally, moisture deficiency can be reversible with the application of occasional irrigation. However, the damage caused by excessive humidity is often irreversible and can cause the death of the plant.
For commercially grown cacti it is advisable to allow the soil to dry out before applying the next watering. Likewise, during the winter rest period, irrigation should be suppressed and started at the beginning of spring as the cactus becomes active.
Fertilization
Cacti are plants adapted to poor soils with a low content of organic matter and nutrients. However, it responds favorably to the application of organic fertilizers with vigorous growth, firm thorns and excellent flowering.
The application of a dose of fertilizer 1:2:3 during the growth period is recommended. To promote flowering, it is favorable to increase the application of potassium and when the formation of flower buds begins, it is advisable to apply a 1:2:4 fertilizer formula.
Temperature
For the…