## 3 Results  
### Photo-Optical Documentation  
The photo-optical documentation (Figure 3) of the development of treated containers in comparison to the control over the experimental time revealed that glyphosate caused a change in colour already 3 days after spray application. After 6-7 days, glyphosate treatment caused dieback of the grass. During the experiment, many challenges were encountered such that one of the three glyphosate-treated containers reacted with a time lag and showed visual symptoms starting on day 6. Eight days after application, the three glyphosate-treated containers showed a comparable appearance. These differences in dieback had a strong effect on the statistics. Despite strong differences between the control and the glyphosate treatment in many of the investigated parameters, these differences became significant only later in the experiment. The drought treatment reacted very slowly because a lot of water was stored in the grass sod. Therefore, it was necessary to elongate the experimental time to show the effect of drought on the investigated parameters. The dry matter content of the control plants and the drought plants was still comparable on day 8 of the experiment (Table 2).  
Figure 3 demonstrate the problem that the visual impression of photograph pictures depends very much on light conditions and can vary with daylight. This is the reason why it was necessary to perform the investigation under controlled light conditions in a darkroom. The pictures in Figure 3 shall only serve as a visualization of the trial.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Index** & **Full Name** & \begin{tabular}{c} **Formula (Wavelength \(\lambda\) in** \\ **[nm])** \\ \end{tabular} & **Sensitivity** & **Reference** \\ \hline \multirow{4}{*}{PSSRa} & Pigment specific & \multirow{2}{*}{\begin{tabular}{c} Simple ratio \\ (chlorophyll) index \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} (\(\lambda_{800}/\lambda_{680}\)) \\ \end{tabular} } & Chlorophyll \(a\) & [20] \\  & Inverted red-edge & \multirow{2}{*}{\begin{tabular}{c} chlorophyll index \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} (\(\lambda_{783}-\lambda_{665}\))/(\(\lambda_{700}/\lambda_{740}\)) \\ \end{tabular} } & Chlorophyll & [21] \\  & Modified anthocyanin & & \multirow{2}{*}{\begin{tabular}{c} (1/\(\lambda_{550}-1/\lambda_{700}\)) \(\times\)\(\lambda_{780}\) \\ \end{tabular} } & Anthocyanin & [22] \\  & reflectance index & & & \\  & Caroenoid reflectance & & & \\ CRI-1 & \begin{tabular}{c} index \\ \end{tabular} & \multirow{2}{*}{\begin{tabular}{c} Photochemical \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} (\(\lambda_{551}-\lambda_{570}\))/(\(\lambda_{531}+\lambda_{570}\)) \\ \end{tabular} } & Photosynthetic & [23,24] \\  & reflectance index & & activity & [23,24] \\ NDLI & \begin{tabular}{c} Normalized difference \\ \end{tabular} & \begin{tabular}{c} (\(\log\)(1/\(\lambda_{1754}\)) \(-\) log(1/\(\lambda_{1680}\)))/ \\ \end{tabular} & Lignin & [25] \\ NDVI & \begin{tabular}{c} Normalized difference \\ vegetation index \\ \end{tabular} & \begin{tabular}{c} (\(\lambda_{800}-\lambda_{670}\))/(\(\lambda_{800}+\lambda_{670}\)) \\ \end{tabular} & Plant structure & [26] \\ NDWI & \
\begin{tabular}{c} Normalized difference \\ water index \\ \end{tabular} &
\begin{tabular}{c} (\(\lambda_{860}-\lambda_{1240}\))/(\(\lambda_{860}+\lambda_{1240}\)) \\ \end{tabular} & Canopy water & [27] \\ \hline \hline \end{tabular}
\end{table}
Table 1: Spectral vegetation indices evaluated in this study.