Spectral indices to rapidly monitor chloroplast distribution patterns of three cecidomyiid galls

The objective of this research was to study altered distributions of chloroplasts in cecidomyiid galls derived from the leaves of Machilus thunbergii Sieb. & Zucc. and Litsea acuminata (Blume) Kurata using confocal laser-scanning microscopy and transmittance spectra. Chloroplasts in all gall tissues gradually decreased in the direction from the exterior toward the inside larval chamber based on Integrated Optical Density (IOD) and absorptivity indices, and chloroplast distributions in various gall tissues were species-specific. Different species of herbivorous insect dramatically altered chloroplasts in their host leaves. The spectral index was significantly and positively correlated with the IOD, and therefore, the transmittance spectra could be utilized as a tool to easily and quickly study the ecophysiology of galls.