The support structure of Cholla cacti provides stabilization via hollow cylindrical struts joined as trusses.

References

"Some cacti (such as the cholla), though, have supportive columns of branched and rejoining struts--trusses in the form of hollow cylinders with perforated walls." (Vogel 2003:437-438)

Book
Comparative Biomechanics: Life's Physical World, Second EditionPrinceton University PressFebruary 28, 2017
Steven Vogel