What are prickles in plants classified as?

Prickles in plants are classified as modified epidermis. They are outgrowths of the outer layer of cells (the epidermis) and can be found on various parts of the plant, such as stems and leaves. These structures serve several functions, including providing protection against herbivores and helping to reduce water loss by creating a barrier.

Unlike modified stems, which involve deeper changes to the plant's vascular system, prickles do not possess vascular tissue. They are more akin to thorns and spines, which have similar protective functions but may differ in their classification and anatomical structure. They are not involved in storage or reproduction, which further distinguishes them from the other potential classifications presented in the choices.