Why do cacti have thorns?

The role of thorns

Cactus thorns, which may seem meaningless to us, are of great significance to the cactus itself. They are a protective mechanism for adapting to the harsh climate.

Normally, most of the water absorbed by plants is consumed by transpiration. According to scientists, for every 100 grams of water absorbed by plants, 99 grams are lost due to transpiration, and only 1 gram is retained in the plant body. The leaves are the main part of transpiration, and most water is lost from here. The larger the leaf area, the faster the evaporation.

Therefore, in order to survive the severe drought and retain as much water as possible, after a long period of evolution, the leaves of the cactus gradually evolved to be more adaptable to the environment, forming the needle-like thorns we see today. This kind of evolution fundamentally reduces the transpiration surface of the plant, saves a lot of water consumption, and greatly improves the survival ability of the cactus in areas with severe water shortages. Those very dense thorns we see are actually the leaves of the cactus.

Evolution of thorns

At present, the thorns of many cacti have changed into other forms. Some have become white hairs, densely covering the surface of the plant. They can reflect strong light and play a role in lowering the surface temperature. At the same time, they also greatly reduce water loss and enable the plant to store a large amount of water. In addition, the number, shape, arrangement, and color of cactus thorns vary greatly, which not only makes them uniquely ornamental, but also becomes an important basis for us to identify cactus species.