There are several theories about what spines are, including one of which says that they are nothing more than leaves that have changed in the process of adaptation to environmental conditions, in which only the middle fibers have been preserved. But it is more correct to consider the needles as evolved kidney scales.
Why do the plants need them?
Cacti acquired their amazing shape in order to ensure their own survival where other species were defeated.
There are a great many purposes for which thorns are needed, here are some of them:
What do the needles of different plant species look like in the photo?
Cacti of the Mammillaria family are not covered with the usual needles; it’s hard to believe that this is a cactus. For example, the spines of Mammillaria lasiacantha resemble feathers in structure, those of Mammillaria egregia look more like snowflakes, and Mammillaria bocasana seem to be wrapped in a white downy cloud. Nevertheless, these are all different forms of spines, adapted to the needs of specific plant species (read about how not to get pricked by a cactus and what to do if this happens).
In less arid regions, spines serve mainly a direct protective function., therefore they grow longer and can be located much less frequently. For example, Cereus jamacaru and Corryocactus brevistylus have needles that can reach 25 cm in length.
The more arid the climate, the shorter and closer together the cactus spines are. This is due to the fact that the protective function fades into the background, and protection against overheating and excessive evaporation of liquid becomes much more important.
Non-thorny flower species
Despite the fact that most associate it exclusively with something prickly, this is not always the case. There are certain ones that do not have spines, for example:
- Ariocarpus fissuratus (stone flower);
- Astrophytum caput-medusae (jellyfish cactus);
- Ophophora williamsii (Peyote cactus).
The adaptive mechanism of cacti, created by nature itself, never ceases to amaze. Thanks to their amazing colors, amazing, sometimes almost alien, shapes and harsh character, it is simply impossible not to pay attention to cacti.
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The cactus is one of the most amazing plants that can survive in the driest areas of the Earth. South and part of North America are called the homeland of cacti.
The structure helps these plants survive in conditions of severe water shortage. Most cacti have a fairly thick main stem, which stores a strategic supply of water.
The cactus has one more feature - very long roots. But the most amazing thing about cacti is their spines, which cover the stem of the plant and are a kind of modification of leaves, the presence of which is characteristic of all plants. The cacti have abandoned their leaves, since they will simply evaporate the moisture that is so necessary in the growing conditions of the cactus.
But how does a cactus survive without leaves? Their function is partially taken over by the stem, which is equipped with stomata. They are closed and absorb the necessary carbon dioxide. Without carbon dioxide, the vital process of photosynthesis for plants is impossible.
In addition to protecting against excess moisture evaporation, the spines, on the contrary, help the cactus obtain much-needed water. The initial function of extracting moisture is provided by the roots of the cactus. They are very long, but located in the upper layers of the soil. Due to them, the cactus covers a large area of soil and can absorb as much moisture as possible.
But the rains in arid areas are extremely rare and sometimes do not wet the soil to the required depth. In such a situation, the cactus, without thorns, would simply die. The thing is that the spines have a unique ability to attract tiny droplets of water electrostatically. You don't have to wait for rain. Temperature fluctuations in the places where cacti grow are quite high, so abundant dew forms in the air, which is the main source of life-giving moisture.
The cactus was worried about its safety by acquiring thorns. Since it stores a large supply of water, which is especially scarce in deserts, many animals are not averse to eating such a juicy fruit. And then large thorns appear to protect the plant, which no animal can cope with.
The spines also help the cactus in the pollination process. They secrete a special nectar that attracts pollinating insects. This ensures the process of reproduction of cacti.
If the cactus grows in a fairly mild climate zone, where there is enough moisture, then the spines on it are quite rare and very long. In this case, they are assigned only a protective function. The more a cactus needs moisture, the more spines there will be on its trunk.
24.09.2014
South America and part of North America are considered to be the homeland of cacti. Evolutionarily, cacti as representatives of the world of flora appeared approximately 40 million years ago. They belong to the succulent plant family. The thorns appeared not as a decorative element, but with meaning. They have evolved over many centuries to become a true survival organ.
The main thick stem of the cactus contains a strategic reserve of nutrient moisture. Another feature of the cactus is its incredibly long roots, which go underground and occupy an impressive radius of the surface in its growing area. Therefore, they can collect life-giving moisture over a fairly large area. Do not think that cacti do not tend to have leaves, like all plants known to us. It’s just that the function of its leaves is performed by these very spines - a modified version of the leaves. The spines are based on a material similar to organic matter - chitin.
Cacti abandoned the leaves of the usual shape for us for a completely objective reason. As a rule, cacti grow in dry places, and wide leaves would be completely irrational and evaporate precious water in large quantities. The functions of the leaves were partially taken over by the thick, fleshy trunk. On its surface there are very thin stomata, which, if necessary, open their pores and absorb carbon dioxide necessary for photosynthesis.
Another unique feature of the spines is that they attract small droplets of water to themselves using electrostatics. Therefore, rain is not always needed for a cactus to drink. In the climate where cacti exist, the temperature fluctuates quite widely. Dew steadily forms in the air, which is a constant source of moisture for cacti.
In addition to the role of getting water, the spines also perform a defensive function. Few of the animal and plant worlds have adapted to survive so successfully in desert dunes, and many animals would gladly feast on such a succulent plant. And this is where the thorns come into the picture, which no animal can handle. Thanks to their spines, cacti are able to be reproductive. The spines secrete nectar, which attracts insects, which act as pollinators.
It is curious that the length of the spines depends on climatic conditions. The milder the climate, the rarer the thorns. But they are quite long, because... They are assigned only a protective function. The drier the climate, the correspondingly more spines there are on the trunk of the cactus. The spines contain large quantities of mineral salts and calcium carbonate. So, in order for the thorns to grow, there must be a sufficient amount of calcium in the soil. That is why you need to add old plaster or marble chips to the soil for growing cacti.
