## 3 Results and Discussion
### Analysis of Variance of the Responses
It is worth noting that the responses that were mainly affected by the factor Distance were the ones associated with water usage, accordingly with the fact that water usage is related to plant heating due to artificial light and, therefore, with light-plant distance (Figure 6). The HR:DB ratio had an influence only on Height (Figure 3) and LAI (Figure 5) responses, and only for the first 25 days of growth. Regarding this factor, when its effect is individually, a negative effect is always reported; therefore, low values of this factor (25%) will generally promote Height and LAI. On the other hand, a positive synergic effect is observed when it is coupled with the employment of White LEDs to promote Height_20D and NoP_25D (Figures 3 and 4). This important achievement demonstrates how different LED light combinations differently affect and promote basil properties at different growth stages. In strong similarity, the addition of White LEDs that was statistically relevant for the responses Height_15D, Height_20D (Figure 3) and NoP_25D (Figure 4), had a negative individual effect on the responses related to Height, but in synergy with HR:DB (Figure 3), it promoted the development of basil height. Again, for the response NoP_25D, an already positive individual effect of the addition of White LEDs was further remarked by the synergy with Distance (Figure 4). From the calculated coefficients reported in Figures 3-6, mathematical models were derived in terms of equations and graphs. Equations were derived by applying Equation (1) and are reported in Table 8, whereas from Figures 7-10, contour plot graphs, representative of the statistically reliable mathematical models, better highlight the achieved results regarding basil growth parameters, according to the explanation given in Section 2.4. Figure 7: Contour plots of the models related to the property Height: (**a**) Height_15D with White LEDs; (**b**) Height_15D without White LEDs; (**c**) Height_20D with White LEDs; (**d**) Height_20D without White LEDs; (**e**) Height_25D. Figure 8: Contour plots of the models related to the property NoP: (**a**) NoP_25D with White LEDs; (**b**) NoP_25D without White LEDs. Figure 9: Contour plots of the models related to the property LAI: (**a**) LAI_20D; (**b**) LAI_25D; (**c**) LAI_30D. Regarding Height, all the models are presented in Figure 7, where it is possible to clearly see that the best conditions to further enhance this property in all the growth stages are: Distance equal to 60 cm, presence of White LEDs and ratio HR:DB equal to 25%. In fact, in the first growth phase (Figure 7a,b) the presence of White LEDs as well as a restrained HR:DB ratio would enhance this response. In the second growth phase (20D), this trend is constant, but a restrained Distance (60 cm) would further enhance the Height at this stage of growth (Figure 7c,d). Finally, in the third stage (25D), the addition of White LEDs is no longer statistically reliable, and only a synergy between a restrained Distance and the lowest HR:DB ratio would further maximize the basil height (Figure 7e). From this it can be derived that White LEDs are absolutely necessary only during the first 20 days, whereas after this time their presence is no longer statistically relevant. Considering NoP, the only reliable model is the one calculated after 25 days of observation, and it is represented in Figure 8. From this model, again the better conditions to maximize this property (Figure 8a) involve the presence of White LEDs and a restrained distance among LEDs and light (equal to 60 cm), while the ratio HR:DB can be chosen without affecting this property. Regarding LAI (Figure 9), considerations quite similar to Height can be made, as the best condition to enhance this property during all the growth phases are driven by restrained Distance (equal to 60 cm) and ratio HR:DB (equal to 25%).