UV-B radiation can be stressful for plants and cause morphological and biochemical changes. Kalanchoe pinnata is a CAM leaf-succulent species distributed in hot and dry regions, and is rich in flavonoids, which are considered to be protective against UV-B radiation.
Nascimento et al. expose plants to supplemental UV-B radiation and find that it causes the formation of brown areas on the leaves, which develop into a protective tissue on the adaxial side of the leaf, but only in directly exposed regions. Anatomically, this protective tissue is similar to a wound-periderm, with outer-layer cell walls impregnated with suberin and lignin. This is the first report of wound-periderm formation in leaves in response to UV-B radiation, and this protective tissue could be important for survival in desert regions under high UV-B stress conditions.