Are vacuolar phenolics effective buffers

Although vacuolar HCAs, HBAs and flavonoids are potent antioxidants, their in vivo scavenging capacity has been questioned because they are not present in the compartments with intense ROS production. The largest part of ROS arises from electron leakage to O2 from the electron transport chains of chloroplasts and mitochondria (Asada, 1996 Moller, 2001). They additionally rise from photorespiration in peroxisomes, from apoplastic NADPH oxidases and various cell wall peroxidases. Most ROS are short-lived species (Moller etal, 2007). The mean half-life in plant tissues is estimated to be 1 o,s, 1 ps, 1 ms, and 1 ns, and their estimated traveling distances are of 30 nm, 30 nm, 1 p.m. 

A second proof comes from wounding experiment of Pseudowintera colorata Raoul (Gould et al, 2002b). In contrast to green leaves, the red ones, enriched in vacuolar antho-cyanins, flavonols, dihydroflavonols, and HCAs, alleviate intensity and duration of the localized burst of H2O2 induced in palisade mesophyll cells by wounding. Vacuolar phenolics participate to scavenge ROS. 

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