Leaves are modified into spines in Opuntia.

Opuntia, commonly known as the prickly pear cactus, is a plant genus known for having modified leaves that are transformed into spines. In Opuntia species, the true leaves are typically reduced in size and function and are often ephemeral or absent. The green, flattened structures that appear to be the leaves are actually modified stems, and the spines or glochids (tiny, hair-like spines) arise from these modified stem structures. These spines serve various functions, including protection against herbivores and reducing water loss in arid environments.