The formation of young stem of cactus

   cactus bears little resemblance to common terrestrial plants. Leafless, fusiform or verrucous plants are also quite different from the techniques of ordinary plants. However, there are also a few cacti with common young stems and leaves in addition to typical cactus flower sets, such as the genus cactus. This genus is a shrub type or small tree type with a large number of branches. Young stems are rounded and slightly fleshy. Generally speaking, the lateral buds of flowering plants grow in the axils of leaves, most of which only become small buds and do not continue to grow. But many plants, such as apple and pear trees, have at least part of their lateral buds growing into short, tender buds. In these tender skills, almost all the new leaves are born in a little bit.

. This is similar to the thorn seat of the cactus, because the thorns of the cactus are actually its abnormal leaves.

The picture shows the young stem of cactus.

   it is true that the leaves of some plants are metamorphosed into spines, such as Berberis, in which various transitional species from spiny leaves to spines have been found. Botanists call these abnormal leaves and buds thorns rather than thorns (only creatures with buds are called thorns, such as raspberries). The thorn of cactus is also formed by the deformation of leaves, so the correct botanical name is also thorn. But in this book, it is still called the thorn according to the custom. When a new bud or flower is produced in the thorn seat, it is clear that there is a bud in the thorn seat. Theoretically speaking

It is possible to sprout new buds in every thorn seat. Remove the new bud above any thorn seat, and the new bud will be pulled out of the thorn seat to replace the removed bud.

   part of the leaf cactus leaves have become very small and narrow. The genus cactus also has leaves, which are round, but soon fall off. The leaf-like basal nodes of many cacti are easily regarded as flattened new leaves. In fact, this kind of cactus has small and weak leaves, and new stem nodes are produced from the thorns on the leaflike stem nodes, while the real new leaves will not grow again.

The round tender stem of    leaf cactus often produces varieties of hump-like, ridge-shaped or ridged stems. at this time, with the growth of the plant, the snail-like thorns are more and more obviously arranged longitudinally. The thorns of the cactus with prismatic stems are also spirally arranged at the seedling stage.

The water storage of    cactus varies greatly with the change of rainy season and dry season, and the ridged structure is especially suitable for this growth mode.

The edge of    became thinner when water was scarce in dry season and thickened when water was sufficient in rainy season, and the overall shape of the plant did not change greatly. In other words, when the surface area of the plant does not change, the internal water storage is very different, just like the pleated box of an accordion. In contrast, the stem nodes of the cactus shrink irregularly when lack of water, and the surface area of the prismatic cactus is larger than that of other species relative to the total volume of the plant (all green plants need a certain surface area to be exposed to sunlight).

The number of    ribs can be increased to a lot, for example, many hairy style cactus plants have very many ribs.

However, the genus Polygonium has the largest number of edges, which can produce as many as 120 cardboard-like thin ribs, while the young stems of many climbing and epiphytic cacti are thin and long, slightly cylindrical or only irregular hump-shaped protuberances. The thicker young stems are angled, and as the plant grows, these edges eventually become winglike, which helps the plant to grow healthily in a semi-shady environment. The three-winged stem eventually produces a two-sided leaf-like flat stem.

On many    cactus plants, the ridges on the ribs are more or less hump-like. If the sun shines directly from above, the ribs will block each other from the sun to a certain extent. Therefore, when the shape of the edges is clearly discernible, you can see that most of the edges are arranged in a spiral shape. If the edges are composed of unconnected and isolated verrucous protuberances, such as progeny ball or mastoid ball, the spiral direction of the edges is difficult to distinguish. On the surface of the plant, only inclined verrucous processes can be seen. Like the arrangement of leaves, the number of verrucous processes in each row is often 5, 8, 13, 21, 34. That is, each number is the sum of the first two numbers, this arrangement enables verrucous processes to be closely and evenly distributed, and to the maximum extent possible not to block each other from the sun.

The cactus with large verrucous protuberances in    is the most different from the common cactus in shape. These verrucous processes look like leaves on the surface, such as Peony or Guangshan, but there is a thorn seat on the verrucous process, in which flowers can be produced, so the verrucous process is not a leaf but a part of the stem. In some small spherical or leaf-shaped cactus plants, such as the genus Lophophora or truffle jade, the spindle ridge can only be identified by the arrangement of thorns.

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