A special adaptation of the
saguaro cactus is the pleated stem. The pleated stem of the saguaro cactus is a useful anatomical adaptation which helps the saguaro to retain water. The pleats allow the saguaro to expand after rainfall, when it takes up water preventing the cactus from bursting. Then as the water is used up the pleats fold again, shrinking the stem. Because of these pleats the saguaro cactus can expand and shrink 25% of its width over one year. The pleats allow the saguaro to retain more water without bursting by unfolding as the saguaro takes in more water. The pleats along with the high amount of parenchyma in the saguaro, cause the saguaro to be approximately 90% water, and because of this water a mature saguaro can weigh more than 6 tonnes.