First, let's look at the spines of cactus for what they really are - the main part of cactus often functions as a modifed stem and its spines are the leaves. The most obvious function of cactus spines are to protect the cacti from animals and peop... read more
Cacti have spines for 1. shade, 2. protection from herbivores, and 3. for helping create new plants (some cacti, like several Cholla species for example, have barbed spines and jointed segments that detach very easily, getting caught in an animals fur or humans clothes/skin - when these segments fall off and come in contact with the ground they root, forming new cacti plants (clones of the parent) thanks to the spines. read more