# A Digital Framework to Predict the Sunshine Requirements of Landscape Plants
## 3 Results and Discussion
### Plant Sensitivity to the Changes of Solar Radiation  
We adopted the regression analysis method to reveal the sensitivity of landscape plants to PPF changes (Supplementary Materials, Figures 4 and 5). In Supplementary Materials and Figure 5, linear regression models are applied for the 15 landscape plants between health levels and PPF. The R\({}^{2}\) and slope values represent the degree of relevance and the sensitivity, respectively. At the same time, the positive and negative values of the slope indicate a positive or negative correlation, respectively, in Figure 4.  
Figure 4: Slope ranking of the linear models in the 15 landscape plant species.  
The results show that _Mahonia fortunei_ ([PERSON].) [PERSON], _Ligustrum quiloui_ [PERSON], and _Rhododendon sinsiii_ [PERSON] are the top three most sensitive plants to changes in PPF (nos. 6, 8, and 9 in Supplementary Materials and Figure 4). Therefore, landscape architects should pay more attention to these plants, especially when the PPF is below 78 umol/m\({}^{2}\cdot\)s, 150 umol/m\({}^{2}\cdot\)s, and 144 umol/m\({}^{2}\cdot\)s, respectively, at which point the health status shifts from healthy to sub-healthy. In contrast, _Podocarpus macrophyllus_ ([PERSON].) [PERSON] and _Aucuba japonica_ var. variegata D\({}^{\prime}\)Om-Brain are only slightly affected by the change in PPF, especially in the ranges of 16-120 umol/m\({}^{2}\cdot\)s and 9-325 umol/m\({}^{2}\cdot\)s, respectively (nos. 2 and 4 in Supplementary Materials). This means that both plants have a wide range of applications and are not limited by the solar radiation variation in urban areas. Meanwhile, for _Aspidistra elatior_ Blume, _Acer palmatum_ 'Atropurpureum', and _Ocalis corymbosa_ DC., the slope of the linear fitting between health level and PPF is negative, which indicates that excessive solar radiation is unfavorable for their health. Related research has revealed that plant height, number of leaves, leaf blade length and width, leaf area, and fresh and dry weights of leaf are greatly increased in grown _Aspidistra_ plants under shady conditions compared with those grown under full sunlight conditions [75]. From this, we can see that the above conclusion supports our fitting results for _Aspidistra elatior_ Blume (Figure 6 and Supplementary Materials).  
However, the effect of solar radiation on plant health is complex for some species. Therefore, our research attempted to reveal these response relationships through nonlinear fitting, as shown in Supplementary Materials. The results show that _Aspidistra elatior_ Blume is a shade-loving plant species, and its health is not affected when the PPF of the planting environment is between 6-107 umol/m\({}^{2}\cdot\)s; however, when the PPF increases to 262 umol/m\({}^{2}\cdot\)s, the health status changes from healthy to sub-healthy. This conclusion has been confirmed in many other studies [75, 76, 77]. For other plants which are not shade-tolerant and cannot tolerate strong solar radiation, such as _Acer palmatum_ 'Atropurpureum' and _Oxalis corymbosa_ DC, the application scope of these plants is relatively narrow. However, planners could overcome this problem through solar analysis and then selecting adaptive plant species for urban greening [20].  
Figure 5: The ranking of the correlation coefficients (R2) for the 15 landscape plant species.