Wound-periderm-like tissue induced by 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

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.

Microchemical tests of transversal sections from the petiole of <em>K. pinnata</em> cultivated during 23 d under supplemental UV-B radiation. Test with Sudan IV on the petiole under a fluorescence microscope using an I3 band pass filter: stronger red colour in the walls of cells immediately above the meristematic tissue (arrow) reveals the stronger suberin impregnation when compared with cells above them (arrowhead).
Microchemical tests of transversal sections from the petiole of K. pinnata cultivated during 23 d under supplemental UV-B radiation. Test with Sudan IV on the petiole under a fluorescence microscope using an I3 band pass filter: stronger red colour in the walls of cells immediately above the meristematic tissue (arrow) reveals the stronger suberin impregnation when compared with cells above them (arrowhead). Full details in Nascimento et al.

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.