Abstract
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 showed that the spectral reflectance was higher than those being parasitized in the visible and near-infrared range. The spectral reflectance in 750~1400 nm was the sensitive range of spectral response of host plant 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, which can be used for chlorophyll content of the parasitic Osmanthus fragrans. There was a significant correlation between spectral parameters and chlorophyll content index. Through the change of spectral parameters, we can predict the chlorophyll content of Osmanthus fragrans under different parasitic degrees. After being parasitized, the leaf functional traits of host plant were generally characterized by large leaf thickness, small leaf area, small specific leaf area, low relative chlorophyll content, high leaf dry matter content and high leaf tissue density. These findings indicate that the host plant have adopted a certain trade-off strategy to maintain their growth in the invasion environment of parasitic plants. Therefore, we suspect that the leaf economics spectrum may also exist in the parasitic environment, and there was a general trend toward the “slow investment-return” type in the global leaf economics spectrum.
Highlights
Parasitic plants are one of the special groups commonly existing in the global ecosystems [1,2,3]
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
Dry matter content and leaf tissue density of Osmanthus 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)
Summary
Parasitic plants are one of the special groups commonly existing in the global ecosystems [1,2,3]. Cuscutaceae is one of the most common parasitic plant species in China, and Cuscuta japonica Choisy is widely distributed [6]. Cuscuta japonica Choisy is seriously short of chlorophyll and other important substances to maintain its photosynthesis due to the degradation of its roots and leaves [6,7] It usually parasitizes the root and stem of the host plant through its special root absorption, and relies on absorbing carbohydrates, inorganic salts and water from the host to maintain its survival, growth and reproduction [8]. Studies have shown that the host range of Cuscuta Japonica Choisy is quite wide, and the vast majority of herbaceous dicotyledonous and monotyledonous plants may become parasitic objects of Cuscuta japonica Choisy. How to monitor and obtain the growth status and the infringed status of the damaged vegetation is the key to effectively prevent and control the infringement
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