## 2 Materials and Methods
### Analytical Methods  
The concentration of dry mass in stevia leaves was determined via the gravimetric method, using a Binder ED400 (Merazet, Poznan, Poland) dryer and a WTC2000 (Radwag, Radom, Poland) analytical scale (Vitamin C concentration was measured in fresh stevia leaves using [PERSON]'s method ([PERSON], 2012). Approximately 10 g of stevia leaves was homogenized with oxalic acid (200 cm\({}^{3}\), 2%) using a Koenic blender. The homogenate was filtered, and \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Month**} & \multirow{2}{*}{
\begin{tabular}{c} **Decade of the** \\ **Month** \\ \end{tabular} } & \multicolumn{2}{c}{**Year 2014**} & \multicolumn{2}{c}{**Year 2015**} & \multicolumn{2}{c}{**Year 2016**} & \multicolumn{2}{c}{**Average in Years**} \\  & & **\multicolumn{1}{c}{} & **[\({}^{\circ}\)C]** & **[mm]** & **[\({}^{\circ}\)C]** & **[mm]** & **[\({}^{\circ}\)C]** & **[mm]** \\ \hline \multirow{3}{*}{May} & 1 st & 11.4 & 30.3 & 13.3 & 12.3 & 15.4 & 14.0 & \multirow{3}{*}{14.2} & \multirow{3}{*}{57} \\  & 2 nd & 12.2 & 33.6 & 13.0 & 14.0 & 15.5 & 12.0 & & \\  & 3 rd & 17.3 & 42.8 & 14.0 & 0.5 & 20.9 & 0.0 & 14.2 & 57 \\  & Monthly average & 13.8 & 106.7 & 13.4 & 26.8 & 17.3 & 26.0 & & \\ \hline \multirow{3}{*}{June} & 1 st & 18.4 & 8.2 & 18.1 & 11.0 & 21.1 & 9.4 & \multirow{3}{*}{17} \\  & 2 nd & 16.6 & 0.3 & 16.4 & 23.1 & 18.5 & 59.0 & \\  & 3 rd & 15.7 & 15.4 & 15.8 & 32.2 & 23.8 & 0.8 & \\  & Monthly average & 16.9 & 23.9 & 16.8 & 66.3 & 21.1 & 69.2 & & \\ \hline \multirow{3}{*}{July} & 1 st & 20.5 & 20.0 & 20.5 & 11.0 & 20.5 & 39.5 & \multirow{3}{*}{19.2} & \multirow{3}{*}{83.4} \\  & 2 nd & 22.5 & 0.0 & 20.3 & 38.9 & 20.1 & 70.5 & \\  & 3 rd & 22.6 & 26.1 & 19.9 & 3.3 & 23.8 & 24.5 & \\  & Monthly average & 21.9 & 46.1 & 20.2 & 53.2 & 21.5 & 134.5 & \\ \hline \multirow{3}{*}{August} & 1 st & 21.7 & 17.5 & 27.2 & 0.0 & 20.4 & 5.8 & \multirow{3}{*}{18.5} & \multirow{3}{*}{71} \\  & 2 nd & 17.4 & 13.1 & 25.2 & 0.0 & 19.7 & 5.0 & \\  & 3 rd & 15.9 & 35.0 & 23.1 & 2.1 & 21.3 & 13.3 & \\  & Monthly average & 18.3 & 65.6 & 25.2 & 2.1 & 20.5 & 24.1 & \\ \hline \multirow{3}{*}{September} & 1 st & 17.2 & 24.1 & 17.1 & 16.4 & 21.2 & 11.5 & \multirow{3}{*}{13.9} & \multirow{3}{*}{45.2} \\  & 2 nd & 18.6 & 21.6 & 18.8 & 0.0 & 19.3 & 45.8 & \\ \cline{1-1}  & 3 rd & 14.0 & 14.3 & 14.1 & 0.0 & 15.0 & 0.0 & \\ \cline{1-1}  & Monthly average & 16.6 & 60.0 & 16.7 & 16.4 & 18.5 & 57.3 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Rainfall and temperature on site of the experiment during the the stevia growth. 10 cm\({}^{3}\) of the resulting filtrate was titrated with 2/6-dichlorophenol (Tillman's reagent) until a persistent light pink colour was present for at least one minute. Chlorophyll a + b and carotenoid concentrations were analysed spectrophotometrically. Fresh leaves (0.4 g) were ground in a mortar with dried sand, calcium carbonate, and a few drops of 80% acetone to form a homogeneous mass. Twenty cm\({}^{3}\) of acetone was used to transfer ground leaves from the mortar to the Schott filtration system, where the homogenous mass was filtered under vacuum. The resulting filtrate was then transferred to a 50 cm\({}^{3}\) volumetric flask, which was filled with 80% acetone and mixed. The filtrate's absorbance was measured in quartz cuvettes (10 mm optical path) at wavelengths of 470 nm, 645 nm and 663 nm. A blank sample was 80% acetone [23]. Reducing sugars were analysed by weighing 20 g of fresh stevia leaves and adding them to 200 cm\({}^{3}\) volumetric flasks, which was followed by the addition of 10 cm\({}^{3}\) of distilled water. Flasks were then heated in the water bath, and the flasks contents were boiled for 30 min. The reducing sugar concentration was determined using the Lane-Eynon volumetric method [24]. Phenolic compounds were measured using the Folin-Ciocalteu method [25] with compounds extracted from approximately 5 g of fresh stevia leaves in 20 cm\({}^{3}\) of 80% methanol.