Chlorophyll fluorescence, spectral properties, and pigment composition of galls on leaves of machilus thunbergii

The objectives of this study were to characterize the fluorescence and spectral reflectance patterns of galled and nongalled portions of leaves of Machilus thunbergii and to understand changes in metabolism subsequent to gall development on the leaf surface. The results showed that the reflectance values of galls at 280 nm (R₂₈₀) and 320 nm (R₃₂₀) were greater than those for normal leaves; this was hypothesized to minimize ultraviolet light damage. The lower photochemical reflectance index and higher red-green ratio in galls than leaves indicated that xanthophyll cycle pigments and the anthocyanin content were higher in galls than in leaves. In contrast, the lower adjusted normalized difference vegetation index (aNDVI) and cold hard band for galls indicated lower maximum quantum efficiencies for photosystem II (Fv/Fm), chlorophyll contents, and pigment-protein complexes in galls than in leaves. Overall, the fluorescence and reflectance analyses suggested that insect infestations reduce photosynthetic efficiency. In addition, there were highly significant and positive relationships between Fv/Fm and both the photosynthetic reflectance index and the cold hard band, indicating that gall infections induced physiological changes that were detected using both reflectance spectra and fluorescence.