The antioxidative role of anthocyanins in Arabidopsis under high-irradiance

To uncover the potential antioxidative role of anthocyanins in vivo in protecting photosynthetic tissues from photoinhibition, the effects of high irradiance HI, 1300 μmol(photon) m⁻² s⁻¹] were studied using detached leaves derived from Arabidopsis wild-type (WT) and the mutant deficient in anthocyanin biosynthesis (tt3tt4). HI stress caused decreased chlorophyll content and photochemical efficiency, but increased cell-membrane leakage and contents of hydrogen peroxide and superoxide radical in the leaves of both Arabidopsis phenotypes, but the WT plants showed better HI tolerance than tt3tt4 mutant. HI caused a significant increase in the 1,1-diphenyl-2-picrylhydrazyl scavenging capacity in WT but not in the tt3tt4 mutant. The anthocyanins could not contribute substantially to light-shielding during the periods of HI stress, because the anthocyanin content in WT was very low and the colour of leaves was the same as in the tt3tt4 mutant. Thus, it was assumed that the better HI tolerance in WT was mostly related to the potential antioxidative role of anthocyanins.