## 3 Results and Discussion  
Changes in Leaf Functional Traits of Osmanthus Fragrans Leaves Parasitized by Cuscutta japonica Choisy  
In this study, six plant functional traits that are sensitive to environmental changes and external stress were selected, including chlorophyll content, leaf area, leaf thickness, specific leaf area, leaf dry matter content and leaf tissue density. As shown in Figure 3, there were significant differences in leaf functional traits of _Osmantthus fragrans_ between healthy leaves and the leaves being parasitic by _Cuscutta japonica Choisy_. The chlorophyll content index, leaf area and specific leaf area of _Osmantthus fragrans_ were significantly lower than those after parasitism, and these indexes gradually decreased (CK > T1 > T2 > T3) with the increase of parasitism intensity. There were significant differences between healthy leaves and parasitic leaves (chlorophyll content index, leaf area and specific leaf area) (Figure 3a,b,e). The reason for the poor growth of _Osmantthus fragrans_ was that _Cuscutta japonica_ plundered water and nutrients of _Osmantthus fragrans_[40; 41; 42; 43; 44]. In addition, due to the overgrowth of the parasitic plant _Cuscutta japonica_, the host plant lacks sufficient light. It is also an important reason for the decrease of chlorophyll content index, leaf area and specific leaf area in plants. Leaf thickness, dry matter content and leaf tissue density of _Osmantthus fragrans_ were significantly higher than those after parasitism, and these indexes gradually increased with the increase of parasitism intensity (CK < T1 < T2 < T3) (Figure 3c,d,f). In this study, the increase of leaf dry matter content and leaf tissue density was the adjustment of _Osmantthus fragrans_ resources after being parasitized by _Cuscutta japonica_. This was an ecological strategy for plants to cope with external disturbances, which aims to improve the nutrient preservation and defense ability of leaves by increasing the leaf dry matter content and leaf tissue density. \begin{table}
\begin{tabular}{c c} \hline \hline
**Spectral Parameter** & **Description** \\ \hline RES & The maximum 1 st derivative of reflectance in the red band (680–750 nm). \\ \hline REP & The wavelength position corresponding to the maximum reflectance in the wavelength band 680–750 nm. \\ \hline RRV & The minimum band reflectance in the range of 640–700 nm. \\ \hline RGP & The maximum band reflectance in the range of 510–580 nm. \\ \hline GPP & The wavelength position corresponding to the green peak reflectance in the wavelength band 510–580 nm. \\ \hline RWSB & The maximum band reflectance in the range of wavelengths from 1550–1750 nm. \\ \hline YES & The maximum 1 st derivative of reflectance in the yellow band (550–582 nm). \\ \hline YEP & The wavelength position corresponding to the maximum reflectance in the wavelength band 550–582 nm. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Spectral parameters and their description. Spectral Characteristics of Osmanthus Fragrans Leaves under the Different Parasitic Intensity of Cuscuta japonica Choisy  
Under different parasitic intensities of _Cuscuta japonica Choisy_, the leaf surface spectral reflectance curves of _Osmanthus fragrans_ were basically the same, but the spectral reflectance values were significantly different (Figure 4). Spectral reflectance values generally decreasing with the deepening of parasitic intensity, and the reflectance values were CK \(>\) T1 \(>\) T2 \(>\) T3. In the visible light to near-infrared 350-1800 nm band, the spectral reflectance of _Osmanthus fragrans_ leaves under different parasitic intensities was the most easily distinguished in the range of 750-1400 nm, which indicate that this band was the sensitive range of host plants' spectral response to parasitic infection. At the same time, this change characteristic was common under different parasitic conditions. In addition, the spectral reflectance curve slope of _Osmanthus fragrans_ leaves has a sharp increasing trend in the range of 700-780 nm.