Anthocyanin accumulation in the illuminated surface of maize leaves enhances protection from photoinhibitory risks at low temperature, without further limitation to photosynthesis

Anthocyanin accumulation in the illuminated sides of leaves seems an effective strategy of some species to reduce the photooxidative risk. Since less light arrives at the chloroplasts because of this accumulation this paper addresses the consequences for photosynthesis and its protection. Gas exchanges, fluorescence, superoxide dismutase activity and xantophyll composition of the maize genotype HOPI and its anthocyanin-lacking mutant W22 were measured in either white or red LED lights, this latter not absorbed by anthocyanins. Photosynthesis did not differ between genotypes under both lights suggesting that neither CO2 supply nor photochemistry were more limiting in HOPI than in W22. Indeed, no major differences in transpiration were detected while DF/Fm (PSII quantum yield) of HOPI in white light was higher than in LED light or than DF/Fm of W22 in both lights. This probably compensated the lower white light absorption of HOPI chloroplasts compared to W22 because of anthocyanins and led to similar rates of calculated electron transport between genotypes. After a leaf exposure to high white lights at 5°C xanthophyll de-epossidation and superoxide dismutase activity were lower in HOPI than in W22. Further, HOPI could be exposed to a much higher irradiance than W22 before Fv/Fm was similarly reduced