Solar and Supplemental UV-B Radiation Effects in Lemon Peel UV-B Absorbing Compound Content. Seasonal Variations.

HILLAL, M; RODRÍGUEZ MONTELONGO, L.; ROSA, M.; GALLARDO, M.; GONZALEZ, J. C.; INTERDONATO, R.; RAPISARDA, V. A.; PRADO, F. E.

PHOTOCHEM PHOTOBIOL

Blackwell Publishing Ltd.

Año: 2008 vol. 84 p. 1480 - 1486

0031-8655

Effects of solar and supplemental UV-B radiation on UV-B absorbing compounds and malondialdehyde (MDA) accumulations in the peel of lemons collected in summer and winter were analyzed. UV-B absorbing compounds were higher in flavedo than in albedo tissue in both seasons; however, the highest values were observed in summer. These compounds were also higher in outer than in inner flavedo surface. Lemons were categorized as sun, semisun and shaded-lemon according to localization inside the tree canopy. Depending on-tree localization UV-B absorbing compounds were higher in flavedo of sun-lemon than in semisun and shaded-lemon. Supplementary UV-B radiation (22 kJ m-2 d-1 UV-BBE) induced UV-B absorbing compound synthesis in on-tree and postharvest lemons. Two min of supplemental UV-B irradiation in summer lemons produced a strong increment (300%) of UV-B absorbing compound content, whereas in winter lemons a slight increase (30%) was observed only after 3 min irradiation. By contrast, UV-B absorbing compound accumulation was not observed in albedo. Malondialdehyde accumulation showed approximately a similar trend of UV-B absorbing compounds. According to our results solar UV-B was not required for UV-B absorbing compound accumulation in lemon peel. Relationships between UV-B absorbing compounds, malondialdehyde, reactive oxygen species (ROS), and pathogen protection were also discussed.