## 4 Discussion
### Efficiency of the Photosystems  
The efficiency of the photosystems is affected by many factors, such as the light intensity, environmental temperature, vegetation density, and biochemical and structural characteristics of leaves. By increasing the specific absorption coefficient of biochemical components in leaves, the retrieval rate can be further improved. Barely any sample exhibited higher levels of variation than a sugar beet. It is noticed that the photosynthesis measurements conducted at the same time showed that sugar beets differed only slightly, with no stress and a high light-cooperation rate, which may explain the higher consistency between the measurement and simulation of ChIP [30]. According to [PERSON] et al. [50], there is a relationship between the increase in ChIP variability and the physiological downregulation of photosynthesis. Under the influence of light with different intensities, the efficiency of energy transfer of each functional unit of PS II was different. Under the appropriate intensity of light, the energy was transferred to the reaction center in a unidirectional optimized mode with low energy consumption; under light of higher intensity, the transfer of energy occurs in the opposite direction. Under the highest intensity light, the photosynthetic organ would have been damaged, resulting in the reduction in light efficiency. A comparative study on diurnal changes in the photochemical activity of PS II in Ginkgo biloba leaves under different weather conditions indicated that, with the change in light intensity, the potential activity and maximum quantum efficiency of PS II on cloudy and sunny days initially decreased and subsequently increased [51]. The effect of the ambient temperature on photosystems efficiency was also significant. High temperatures can inhibit the activity of the electron transfer chain on both the donor and receptor side of PS II; however, the donor side of PS II is more sensitive to high temperatures than thereceptor side is. Correspondingly, low temperatures can also damage the reaction center and receptor side of PS II in the leaves. In addition, under the same light conditions, high vegetation density induced the decline of the actual PS II photochemical quantum efficiency, inhibiting the photosynthetic capacity and PS II function of the leaves and leading to a decline in the PS II utilization of light and the enhancement of excitation energy dissipation. From the context of the vegetation itself, the biochemical and structural characteristics of the leaves in this vegetation would also have an impact on light efficiency. By increasing the specific absorption coefficient of biochemical components in leaves, the light efficiency can be further improved. Thus, in the experiment, it is difficult to quantitatively determine the efficiency of the light system because of the different plants and their different properties. At the same time, our measurement equipment did not support the measurement of optical system efficiencies I and II. The Fluspect model with the FQE inversion code reduced the error at the peak of the curve. Except for PS II and PS I, other parameters with the FQE inversion code were almost unchanged compared with those retrieved by the model without the FQE inversion code (see Table 3), implying that PS II and PS I play a dominant role in producing the fluorescence. Although the photosystems are characteristics of the plants themselves, they also tend to depend on natural conditions. The measurement of the emission efficiency of the photosystems is complex. As a result, the values of PS II and PS I could not be easily measured in this study. Therefore, the model with the new code still needs more tests to verify PS II and PS I. Some may argue that a separate adjustment of the fluorescence from the two photosystems is still necessary, so we compared our results to other studies on the spectral shape of leaf fluorescence, such as [PERSON] et al. [22]. In previous studies, [PERSON] et al. [30] described the Fluspect model, and [PERSON] et al.