In cacti, the spines are modified leaves. Spines are sharp, needle-like structures that grow from the areoles, which are small, rounded structures on the surface of the cactus. These spines serve multiple purposes for the cactus. They act as a means of defense against herbivores, preventing them from consuming the plant`s tissues. Spines also help to reduce water loss by providing shade and reducing air movement around the surface of the cactus. Additionally, spines can help in capturing dew or moisture from the air, allowing the cactus to survive in arid environments. While the stem of a cactus can also be modified to store water, it is the leaves that are specifically modified into spines in cacti.