Protection Mechanism Of Anthocyanin To Apple Leaves And Fruit Peel Under High Temperature And High Light Stress

Anthocyanin may protect plant from stresses via light attenuation or scavengingreactive oxygen species directly. High temperature coupled with high light is a type of stressplants often suffer. It is important to clarify the protection mechanism of anthocyanin to planttissue under high temperature and high light.1. Leaves of Malus royalty and Malus micromalus were compared in terms of promptfluorescence,delayed fluorescence and modulated light reflection at820nm under hightemperature and high light （red light or green light） stress. The results showed that beforestress treatment, there was almost no difference between Malus royalty leaves and Malusmicromalus leaves on prompt fluorescence, delayed fluorescence and modulated lightreflection at820nm. High temperature and high light damaged the photosynthetic electrontransport chain of the leaves. When leaves were treated by high temperature, the damage ofphotosynthetic electron transport chain was less severe under green light than that under redlight, and this difference was greater in Malus royalty leaves, indicating that anthocyaninalleviated the damage of leaves by absorb green light under high temperature and high lightstress. When leaves were treated by high temperature alone, the damage level of Malusroyalty leaves was significantly lower than that of Malus micromalus leaves. However, whenthe high light （red light） stress was combined, the damage levels of the two kinds of leaveswere greater than that under high temperature. However, the difference of damage levelsbetween the two kinds of leaves decreased under high red light coupled with high temperaturecompared to that under high temperature alone, suggesting that anthocyanin was not involvedin scavenging reactive oxygen species in apple leaves in vivo under high temperature and highlight.2. Peels of ‘Golden Delicious’ apple were used to identify protection mechanism ofanthocyanin to apple leaves under high temperature and high lightstress. The results showedthat the phenolics extracted from ‘Golden Delicious’ apple peel had a strong ability for scavenging hydrogen peroxide (H2O2). After incubating with H2O2for30min,cyanidin-3-galactoside concentrations in the phenolic extract decreased as H2O2concentrations increased. In contrast, the concentrations of other phenolic compoundsremained unchanged. Exogenous application of H2O2enhanced the synthesis of phenolics,especially anthocyanin, in ‘Golden Delicious’ apple peel under sunlight. After incubating thepeel extract of H2O2-treated apples in the dark for30min, the concentration ofcyanidin-3-galactoside significantly decreased to a greater extent than that of other phenoliccompounds. Based on these data, anthocyanin is more sensitive to H2O2and contributes moreto H2O2scavenging than other phenolic compounds in vitro, while anthocyanin could notscavenge H2O2in vivo under high temperature and high light.