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Cacti occupy a special place among the whole variety of indoor plants and differ from them both in appearance and in keeping conditions. In Hellas, the ancient Greeks called cacti (kaktos) any thorny plant, like a thistle, which grow in abundance in nature. Much later, Columbus brought the first cacti to Europe, rare amazing plants were in the collections of the royal botanical gardens.
In 1571, the French botanist Mathias Lobel, in collaboration with Pierre Pena, in the illustrated book "Adversaria Stirpium Nova" described 1,500 species of various plants, indicating the settlements where these species were collected, here was Melocarduus echinatus (the modern name Melocactus caroli-linnaei) … And in 1753 the famous Swedish botanist Karl Linnaeus used this word "Cactus" in his two-volume work "Species Plantarum", while all the discovered and described plants belonged to a single genus - Cactus.
The cactus family came to Europe exclusively from the New World, i.e. North and South America. With the exception of the genus Rhipsalis, which was discovered in tropical regions of Africa, but, according to scientists, got there artificially, or rather with migratory birds. Now cacti are widespread, took root and became native in the Mediterranean, South Africa and Australia.
But the main distribution area of cacti is mainly South and North America, Mexico is especially rich in a variety of cacti. Most cacti grow in areas subject to prolonged periods of drought, some are found in extremely dry conditions, for example, the Atacama Desert (Chile is the driest desert with the Copiapoa genus cacti growing there).
About cacti, it must be said, first of all, that they all belong to succulent plants (succulents are plants that have the ability to store or accumulate water in their cells). Most cacti do not have leaves; more precisely, the leaves have been modified into thorns, and the stems perform the photosynthesis function inherent in all plants.
Кстати, кактусам (в подавляющем большинстве) свойственен САМ-тип фотосинтеза, характерный для многих суккулентов, когда происходит разделение ассимиляции CO2 и цикла Кальвина. Транспирация, в ходе которой углекислый газ проникает через устьица, и образуется соль яблочной кислоты (малат - накапливается в вакуолях клеток), происходит не днем, как у обычных растений, одновременно с фотосинтезом, а ночью. Днем же, когда устьица закрыты, осуществляется декарбоксилирование этой кислоты, а освобождающийся углекислый газ поступает в цикл Кальвина, и участвует в процессе фотосинтеза. Такая система позволила кактусам адаптироваться к высокой интенсивности света, повышенным температурам и засухе.
The stem of a cactus is called its body, or trunk. The stems of some cacti in nature reach tens of meters in height, real trunks, so Pachycereus Pringlei Pachycereus pringlei, originally from Northern Mexico, is the tallest cactus in the world, the maximum height recorded by naturalists is 19.2 m. Another giant, also from Mexico and California - Cereus giant Cereus giganteus. Its growth rate, like that of our Russian birches and pines, is very slow, and the average trunk size is 15-17 m.And here is one of the smallest cacti - Blossfeldia tiny Blossfeldia liliputana, its diameter is about 1 cm.
A feature of any cactus that distinguishes them from other succulents (some are extremely similar to cacti) is that they have areoles. The areola is a modified axillary bud, which is the growth point. In the same way that ordinary plants have apical and lateral buds, a cactus has an apical areola, the so-called axilla and lateral areoles.
Many cacti are able to stop growing from the axilla at some point and start developing shoots from the lateral areoles. This ability is genetically assigned to individual plant species. That is why "babies" form mammillaria so easily, and cereus grow literally in a column. It is from the areoles of the cactus that thorns grow and flowers appear (in some species of cacti, flowers do not appear from the areola, but next to it, literally breaking through the epidermis, which is typical, for example, of Echinocereus).
Areoles, or rather their size, shape, color of bristles, location (distance between areoles), as well as the number of spines (radial and central - growing exactly from the center of the areola), are an essential feature that determines the attitude of a cactus to a particular species. In some cacti, a sweet syrup is released from the areolas, freezing, it looks like sugar crystals, and the same sweet taste. When too much of this syrup is released, it is better to remove it from the cactus gently with tweezers or a needle.
Thorns and thorns on cacti serve not only to protect against predators, but also provide protection from the sun. Even though the thorns are usually thin, often very sparse, the sun moves throughout the day and each thorn always casts a shadow on a different part of the stem.
Therefore, the more thorns a cactus has and the thicker they are, the more the plant is adapted to the direct scorching sun. Cacti with short, sparse thorns or almost no spines usually require sun protection during the hottest hours of the day.
Another interesting feature is that cacti do not form inflorescences, the flowers are usually single, bisexual (with the exception of some species), and do not have a peduncle. Moreover, in a cactus, part of the flower is a continuation of the stem, while the lower part of the corolla tube has areoles, bristles, and spines. This applies to almost all cacti, with the exception of mammillaria.
Sometimes a bud that begins to grow turns into a baby (this usually happens when overfeeding with fertilizers). In some cacti, only one flower appears, each time in a new place, in other cacti, during flowering, many flowers are formed throughout the stem (aporocactus), in others, the flowers form a crown - they are located in a wreath on the crown of the trunk. The size of flowers can be from microscopic (a few millimeters) to very large - 15-20 cm in diameter. The color of cactus flowers can differ in a huge variety of colors and shades, however, cacti do not have blue and black flowers, only shades of brown can be the darkest.
Some cacti bloom easily every year, some bloom rarely or only under the best conditions. Flowering in different cacti can last for several weeks, or can be calculated only in hours. After flowering, fruits are formed on cacti, which can also be of various shapes, sizes, and often covered with thorns.
The stems of cacti have different shapes. It can be ribbed, wrinkled, have bumps or papillae. Ribs may be vertically straight, spirally curled, or slightly curved. The ribs are sometimes almost invisible, sometimes the ribs are deep and sharp. And the thorns can be of completely different shapes, lengths, structures and colors, some cacti do not have thorns at all. In appearance, cacti are so diverse that more than one book is devoted to their description. It happens that completely unrelated cacti are outwardly so similar that they can be confused, but there is always a difference, as a rule, it lies in the structure of the flowers.
Classification of cacti
The cactus family includes four subfamilies that have a fundamental difference in structure and physiology:
At present, it includes only one genus Pereskia Pereskia (17 species) - cacti that have completely preserved their true leaves. Representatives of this subfamily are mainly shrubs, with round stems and flat leaves, from the areoles that are located in the axils of the leaves, there may be spines, usually straight and hard. Flowers of cacti of this subfamily can be single on pedicels, or they can be collected several in racemose inflorescences. Most of the pereskievs have edible fruits.
Interestingly, Pereskia is of great evolutionary importance - it is actually a visual aid for the transition from one form of plants to another, combining the characteristics of various plants - they have photosynthesis mainly according to the C3-type, like in ordinary leafy plants (mesophytic type of metabolism), but more A detailed study of Presky showed that at night there is still a slight increase in carbon dioxide in the tissues, which indicates a low level of CAM-type (only in some species). (Photosynthetic pathway variation in leafy members of two subfamilies of the Cactaceae, Martin, Craig E. Wallace, Robert S., 2000).
In addition, pereskia have areoles and spines, like all cacti. Of course, the thorns themselves are not a sign of a cactus, you say - that's right, but in the Peres areoles and thorns are also located on the flowers, and this is an exclusively cactus sign. Moreover, such a phenomenon as proliferation is characteristic of pereskia - when new daughter flowers or adventitious shoots are formed from the areola on the flower tube or ovary.
Description of Pereskiev species
Subfamily of Pereskii
Opuntia subfamily Opuntioideae
Includes 5 tribes - shrubs with succulent flat or cylindrical stems. All prickly pears have a characteristic segmented stem structure, but in some, the stem segmentation is very weak.
The smallest prickly needles (glochidia) are characteristic only of the opuntia subfamily. In addition, prickly pears at a young age have modified leaves that fall off with age. Flowers are single, regular shape. The fruits of many opuntia are edible.
Opuntia Opuntia, as well as peresia, is also characterized by the phenomenon of proliferation. As for photosynthesis, in the studies of representatives of this family, gas exchange processes were recorded throughout the day; in Opuntia, there is a combination of CAM-type and C3-type photosynthesis.
Includes only one genus (2 species, formerly part of Peresky), whose representatives grow at an altitude of 2000-2400 m above sea level in the Andes (the territory of Argentina and Chile).
Plants are similar in appearance to prickly pears, but there are no glochidia. Like prickly pears, maihuenias have tiny, up to 10 mm succulent leaves of a conical shape, and the seedlings are very similar to those of deciduous plants. Despite the pronounced succulence, the plants of this subfamily do not possess CAM metabolism - their photosynthesis proceeds according to the C3-type, like in Pereskia Pereskia, CO2 absorption occurs during the day.
Plants are rare and almost never found among domestic cacti.
Subfamily Cactaceae Cactoideae
It makes up more than 80% of all other cacti, this is what is called typical cacti. Their main difference is that the leaves are completely absent, and they do not have glochidia either. The stems of cactaceae are usually whole, with no segmentation, except in the genera Hylocereeae and Rhipsalideae. The overwhelming majority have thorns. Flowers are sessile, remain open during the day or only at night. Seeds are small, 0.1 - 2 mm, mostly black, glossy.
Among the cactus there are many edible plants - plants from the genus Stenocereus, Hylocereus are specially cultivated for the sake of fruit. There are edibles among the genera Echinocereus, Ferocactus, Mammillaria, Myrtillocactus, Pachycereus, Peniocereus and Selenicereus. The natives of Bolivia even bake cacti of the Neowerdermannia vorwerkii species and eat them like potatoes.
It should be noted that the studies of genetic biologists do not stand still, many classification issues remain controversial, and it is likely that the classification of cacti may change again in the near future.
Brief requirements for soil, temperature, lighting - the article contains reference characteristics on the requirements of certain genera of cacti for temperature, illumination, soil composition, etc. There are characteristics of the root system and the origin of each genus and plant species.
In conclusion, about cacti, I would like to say that it would be a mistake to consider them all unpretentious plants. It is not entirely clear why in all the literature, as by agreement, they write about the unpretentiousness of cacti, because in fact this is not at all the case. For different authors, the idea of unpretentiousness is reduced only to the fact that cacti do not require frequent watering. But water is not the only condition for plant life.
Judge for yourself, an excess of water - and a cactus rotted, a lack of light - a twisted ugly stem, fed with organic fertilizer - and a cactus may die, transplanted into a too large bowl - a cactus may not bloom and even hurt for a long time, but the fact that most cacti require cold wintering, doesn't he say that these plants need special care ?!
Undoubtedly, there are among the cacti and particularly unpretentious, which bloom easily and do not require special attention, but there are not many of them. Therefore, a novice lover of cacti should especially pay attention to the nature of the future pet.
It should also be added that many cacti are prone to corking the stem when a brown crust appears on the lower part of the trunk, usually in the root zone. It is formed from contact with wet soil, if it dries for a long time, especially if the water is hard, contains a lot of salts, especially from excess fertilizers in dressings. The salt brown crust on a cactus is simply determined: if you try to pick off the crust (for example, with a toothpick), healthy epithelial tissue of the stem will be found under it, but of a lighter shade (because its ultraviolet is not available). However, you do not need to tear off such cork salt build-ups, the appearance of the cactus will still be spoiled, and you can easily injure the plant.
Brown crusts and spots can appear higher along the trunk from sunburn, pests, mechanical damage.