## 2 Material and Methods
### Models for Indirect Measurement of Basic Plant Characteristics  
The amounts of chlorophyll, carotenoids, flavonoids, anthocyanins, and nitrogen were calculated. Data from the chlorophyll content index (_CC_) [1], determined at specific spectral wavelengths in the VIS and NIR ranges, were used. T931 is transmittance at 931 nm (NIR spectral range), and T653 is transmittance at 653 nm (VIS spectral range).  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Characteristic** & **Description** \\ \hline Chlorophylls & Chlorophyll is a green pigment in plants that has a critical role in photosynthesis. Measuring the chlorophyll content of plants can provide insight into their health, growth, and stress responses. \\ \hline Carotenoids & Carotenoids are pigments that are responsible for the orange, red, and yellow colors of plants. In addition to their role in coloration, carotenoids also have important functions in photosynthesis and plant protection against environmental stressors. \\ \hline Flavonoids & Flavonoids are a diverse group of plant pigments that have a wide range of functions, including UV protection, pollinator attraction, and defense against pathogens and herbivores. Measuring the flavonoid content of plants can provide insight into their responses to biotic and abiotic stressors. \\ \hline Anthocyanins & Anthocyanins are water-soluble pigments responsible for the red, purple, and blue colors of plants. In addition to their role in coloration, anthocyanins also have important functions in protecting plants from UV radiation and environmental stressors. \\ \hline Nitrogen & Nitrogen is an essential nutrient for plant growth and development, playing a critical role in physiological processes such as photosynthesis and protein synthesis. Measuring the nitrogen content of plants can provide insight into their nutritional status and also be used to optimize fertilization practices. \\ \hline \hline \end{tabular}
\end{table}
Table 1: Description of main characteristics of plants considered in this work.  
Chlorophyll content (CC) was determined using the formulas presented by [PERSON] et al. [15]. The carotenoid content (\(CrC\)) was determined after converting formulas presented by [PERSON] et al. [16] and [PERSON] et al. [17]. Equations for flavonoids were derived from data from [PERSON] et al. [18], [PERSON] et al. [19], and [PERSON] et al. [20]. Anthocyanin content (\(AC\)) was determined after the conversion of a formula presented by [PERSON] et al. [21]. The nitrogen content (\(NC\)) was obtained using a formula presented in [22].  
The determination of pigments and nitrogen in plants from data from \(CCI\) measurements has the following advantages: the method is non-destructive and allows for quick and convenient correlation with other main characteristics of plants and their growing conditions. Of course, some limitations can also be pointed out, such as indirect evaluations and differences with laboratory measurements of the respective pigments.  
Chlorophyll Content Index \[CCI=\frac{T931}{T653}\text{, a.u.}\] (3) Chlorophyll Content \[CC=-84.3+98.6 CCI^{0.505}\text{, }\upmu\text{mol}/\text{m}^{2}\] (4) Caroenoid Content \[CrC=-496.53037+449.76517\times CCI^{0.215}\text{, mg}/\text{g}\] (5) Flavonoid Content \[FC=-23.09896+12.67864\times CCI^{0.215}\text{, mg}/\text{g}\] (6) Anthocyanin Content \[AC=-5.28456+2.37404\times CCI^{0.215}\text{, mg}/\text{g}\] (7) Nitrogen Content \[NC=-3.5389+3.33079\times CCI^{0.215}\text{, }\upmu\text{mol}/\text{m}^{2}\] (8)  
The \(CCI\) was calculated according to the technical specifications of a company (Opti-Sciences, Inc., Hudson, NY, USA). Chlorophyll content (CC) was calculated according to a generalized model presented by [PERSON] et al. [15].