Multiple functional roles of flavonoids in photoprotection

Flavonoids have long been recognized as playing multiple roles in the responses of higher plants to a wide range of environmental constraints (Winkel-Shirley, 2002; Roberts & Paul, 2006), and early proposed as developmental regulators (Stafford, 1991). Over the last three decades, as ozone depletion has become a major environmental problem, the particular role of flavonoids in screening short-wavelength solar UV-B radiation (over the 280–315 nm waveband) has been strongly emphasized (Rozema et al., 1997; Burchard et al., 2000). It is now well documented that UV-B stress greatly enhances the production of reactive oxygen species (ROS), as occurs in response to a plethora of environmental stresses (Apel & Hirt,…