Multiple functional roles of flavonoids in photoprotection

Here, we offer evidence that may challenge the view that light-inducible ‘UV-absorbing flavonoids’ function primarily in attenuating short-wavelength solar UV-B radiation. We propose that UV-absorbing flavonoids serve an important antioxidant function in photoprotection. Our suggestion is based upon: the UV-screening and antioxidant properties of UV-inducible flavonoids; their accumulation in the mesophyll, not only in epidermal cells following sunlight exposure; the minor role of effective UV attenuators, such as hydroxycinnamic acid derivatives, in the response of plants to sunlight irradiance; and the high capacity of antioxidant flavonoid structures to regulate auxin movement.