Doornen

Doornen: thorns and spines present on many plants are a form of modified leaf tendrils or needle-like structures that serve as a defense mechanism against herbivores. They are commonly found on woody shrubs such as roses (Rosa spp.) and hedges, as well as in succulent species like cacti (Cactaceae). The morphology of a thorn varies: true thorns derive from vegetative tissue, whereas spines are modified leaves or stipules. The chemical composition of thorns is similar to the surrounding plant tissue, but the physical structure helps deter animals from chewing.

The evolutionary advantage of thorns is well documented. Plants with sharp defence structures experience lower grazing pressure, increasing their probability of reproduction. In ecosystems where herbivores are abundant, thorny plant species often dominate. Conversely, in habitats with limited grazing, thorns may be reduced or absent. Some plants, such as the Arakanese tree and the fig tree, have evolved specialized thorn systems to protect reproductive parts. In contrast, some succulents utilize thorns for shading and to reduce water loss.

Human uses of thorns have included weaving and decorative purposes. Rose thorns were historically used in medieval times for needle making and the production of fine jewelry. In some cultures, cactus spines are employed as a natural abrasive to clean dishes or as protective barriers against livestock. Most commonly, thorns are considered an obstacle to gardeners, leading to the selection of thornless cultivars for ornamental horticulture and low-maintenance landscapes.