Detailed Explanation of the Leaf and Root Characteristics of Cacti

  Cactus Spines

  Almost every cactus plant has different spines. Spines are often divided into two types, namely central spines and radial spines. Central spines grow from the center of the areole and are hard in texture, while radial spines grow on the edge of the areole, either sparsely or densely arranged close to one another. Radial spines and central spines may have obvious differences, for example, the central spines are longer, hard and strong, while the radial spines are fine and flexible. This is because the two have different functions: the central spines protect the plant from external attack, and they usually have a color that attracts attention from a distance. The radial spines are often white and relatively slender, and their main role is to protect the plant from excessively strong ultraviolet light by reflecting sunlight.

Pictured: cactus spines

  In addition to central spines and radial spines, there are also many spines with special shapes. However, these special spines are limited to certain species and are not a characteristic of a whole genus. More common are spines with hooked tips, such as many species in the genus Mammillaria (MammZZarla); this kind of spine is especially worrisome because people can easily be hooked by it when they are not paying attention. Strong animals may pull the entire cactus out of the soil, so this kind of cactus can attach to the fur of large animals and thereby achieve reproduction in a different place.

  The most worrying spines are not the huge needle-like spines of certain species in the genus Ferocactus, but the so-called hooked spines. Hooked spines are found only in cactus subfamily plants and are an important basis for identifying these species. The longest hooked spines are only a few millimeters long, very slender, and brittle. Only with the help of a high-power magnifying glass or a microscope can many tiny barbs be seen clearly. Hooked spines easily pierce the skin and break off once they enter the skin. Because of the barbs, muscle movement causes the broken spine to go deeper and deeper, causing pain that lasts for several days, until the broken spine is finally picked out. Therefore, friends who like cactus plants should be especially careful.

  Usually only epiphytic cacti do not grow spines. Conversely, spineless cacti in arid open areas are all exceptions. For example, the genera Lophophora and Strombocactus, as well as Astrophytum asterias, at least as people already know, the plants of the genus Lophophora contain toxic sap in their bodies, which can replace sharp spines in the role of protection. The main component of their venom is the alkaloid mescaline. This is a highly toxic drug used by the Indigenous peoples of the Americas. In addition, the nearly spineless genus Peniocereus also contains a special chemical substance that can treat heart disease - glycosides. For this reason, people even cultivate large-flowered Peniocereus "Queen of the Night" in large quantities in greenhouses. And the milky sap that plants of the genus Mammillaria immediately exude when injured also protects the plant from insect attack .

  In addition to differences in the types of spines, different species and genera each have their own strengths in spine length, number, and color. The spine morphology of the same species of cactus does not differ much. But the spines on each areole of the same plant are not all the same. The number of spines and their morphology are closely related to nutrients, water, and light conditions.

  Cactus Roots

Pictured: cactus root system

  People do not fully understand the root structure of most plants, and the same is true for cacti. So far, people can only distinguish a few different root types. The vast majority of cactus plants have very long and slender fibrous roots, which help the plant absorb water from the surface of the ground over as large an area as possible. Because if rainfall is not heavy, water cannot penetrate deep below the surface layer, so in arid areas, a root system that extends very far and can reach groundwater is of great benefit to plant growth . Of course, the root system of cactus plants cultivated in flower pots is completely different from that of wild cacti in desert areas, but this does not harm their growth. Cacti with radish-type root systems, such as species in the genera Gymnocalycium and Lophophora, and the genus Ariocarpus, peony and others, have particularly strong drought tolerance, and the root systems of these species and genera can also store water. Because in hot summers, the temperature a few millimeters below ground is noticeably lower than at the surface. Compared with the plant body above ground, the roots below ground are less vulnerable to high temperatures.