The Changes of Leaf Reflectance Spectrum and Leaf Functional Traits of Osmanthus Fragrans are Related to the Parasitism of Cuscuta Japonica

Abstract Background: Studies on the influence of parasitism on plants based on hyperspectral analysis have not been reported so far. To fully understand the variation characteristics and laws of leaf reflectance spectrum and functional traits after the urban plant parasitized by Cuscuta japonica Choisy. Osmanthus fragrans (Thunb.) Lour. was taken as the research object to analyze the spectral reflectance and functional traits characteristics at different parasitical stages. Results: Results showed that the spectral reflectance was higher than the parasitic reflectance in the visible light and near infrared. The spectral reflectance in 750 ~ 1400 nm was the sensitive range of spectral response of host plants to parasitic infection, which is universal at different parasitic stages. We established a chlorophyll inversion model (y=-65913.323x+9.783, R2=0.6888) based on the reflectance of red valley (minimum band reflectance in the range of 640 ~ 700 nm), which can be used for chlorophyll content of the parasitic Osmanthus fragrans. There was a significant correlation between spectral characteristic parameters and chlorophyll content index. Through the change of spectral parameters, we can predict the chlorophyll content of Osmanthus fragrans under different parasitism degrees.Conclusion: After the host plant was invaded by parasitic plants, its leaf functional traits are generally characterized by thick leaf, small leaf area, small specific leaf area, low relative chlorophyll content, high dry matter content and high leaf tissue density. These findings indicate that the host plant have taken certain trade-off strategy to maintain their growth in the environment invaded by parasitic plants. Therefore, we suspect that there may be leaf economics spectrum in the parasitic environment, and there was a general trend toward "slow investment-return" in the global leaf economics spectrum.