Photoprotective roles of anthocyanins in Begonia semperflorens

Anthocyanins are thought to provide photoprotection under stressful conditions. We used two genotypes of Begonia semperflorens with different pigmentation to study the effects of anthocyanins on tolerance of high-light stress. The maximum quantum yield of PSII (Fv/Fm) in red leaves was significantly higher than that in green leaves during and after high-light stress. High light also induced significant increases in anthocyanins in both genotypes. Despite large differences in anthocyanin content, chlorophyll content and Chl a/b ratio did not differ between red and green leaves. After high-light stress, xanthophyll pool size and enzymatic antioxidant activity were lower in red leaves than in green leaves. Non-enzymatic antioxidant activity measured by DPPH assay, however, was significantly higher in red leaves than in green leaves. Meanwhile, changes in DPPH activity were closely correlated with changes in anthocyanin content during and after high-light stress. Declines in Fv/Fm were significantly greater for green leaves than for red leaves under green light but were comparable between green and red leaves under red and blue light. Changes in ROS under different colors of light were similar to the changes in Fv/Fm. Our results suggest that anthocyanins primarily function as light filters rather than as antioxidant molecules during high-light stress in B. semperflorens.