Do anthocyanins function as antioxidants in leaves? Imaging of H2O2 in red and green leaves after mechanical injury

Abstract

Purified anthocyanin extracts show strong antioxidant properties in vitro, but it is not known whether they can scavenge reactive oxygen in living cells. The oxidative responses in red and green portions of Pseudowintera colorata leaf laminae were compared by the real‐time imaging of H 2 O 2 in cells after mechanical injury. An oxidative burst was elicited almost immediately from chloroplasts in the palisade mesophyll, as evidenced using the fluorochromes dichlorofluorescein and scopoletin. H 2 O 2 accumulated in green lamina regions for 10 min, and then decreased slowly. By contrast, red regions recovered rapidly, and maintained consistently low levels of H 2 O 2. Infusion of cells with N‐acetyl‐l‐cysteine accelerated the depletion of H 2 O 2 from green regions. Wounded leaves ultimately developed a localized necrotic lesion and an intense anthocyanic band. The red regions were enriched in anthocyanins, flavonols, dihydroflavonols, and hydroxycinnamic acids. Only the anthocyanins were suitably located to account for the enhanced rates of H 2 O 2 scavenging. The data support the hypothesis that red cells have elevated antioxidant capabilities in vivo.