## 3 Results
### Microstructure Analysis with the Inverted-Plate Optical Microscope  
In the analysis undertaken with the inverted-plate optical microscope, the diameter of tomato, pepper, zucchini, cucumber and aubergine stems was accurately determined (see Table 6). In addition, the depth of the folds formed in the collenchyma/cortex (the exterior layer of the stems) due to moisture loss was also determined. Furthermore, the porosity of the stems belonging to the Solanaceae plant family, which were characterised by a differentiated path and porosity that was discernible under microscopic examination, was the subject of study in order to establish a range of the lightening of the building material that has been added with these fibres. As shown in Figure 11A-E and Table 6, a comparison of the cross-sections of the tomato, pepper, zucchini, cucumber and aubergine provides insights into the geometry and size of the stems under investigation. The mean diameter of the stems of Solanaceae plants following the drying process ranged from 3273 \(\pm\) 1114 \(\mu\)m to 6155 \(\pm\) 1255 \(\mu\)m. The \begin{table}
\begin{tabular}{c c c} \hline \hline
**Resolute Type** & **Stem Diameter After Drying (\(\mu\)m)** & \(\Delta\)**Diameter vs. Fresh Stem and** \\  & & **Dry Stem (\%)** \\ \hline Tomato & 6155 \(\pm\) 1255 & \(-\)16.66 \\ Pepper & 5698 \(\pm\) 2269 & \(-\)27.54 \\ Zucchini & 17,287 \(\pm\) 7403 & \(-\)30.87 \\ Cucumber & 2065 \(\pm\) 387 & \(-\)63.71 \\ Aubergine & 3273 \(\pm\) 1114 & \(-\)33.04 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Details of stem diameters after drying process. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Resolute Type** & **Tensile Strength (MPa)** & **References** \\ \hline Tomato & 10.68 & Current research \\ Pepper & 13.97 & Current research \\ Zucchini & 3.29 & Current research \\ Cucumber & 19.83 & Current research \\ Aubergine & 16.60 & Current research \\ Jute & 249; 393–773 & [61,62] \\ Coir & 90; 175 & [61,65] \\ Flax & 500–900; 500–1500 & [58,66] \\ Alfa fibres & 75–154; 87 & [57,67] \\ Oil palm fibres & 71 & [59] \\ Glas fibres & 308 & [68] \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Details of tensile strength results compared with high-performance fibres. zucchini stem demonstrated the greatest mean diameter, measuring 17,287 \(\pm\) 7403 \(\upmu\)m. The substantial variation in stem thickness between the root zone, characterised by the largest diameter, and the upper zones, exhibiting the smallest diameter, was evident. The average diameter of the cucumber stem was the smallest, with a value of 2065 \(\pm\) 387 \(\upmu\)m. The deviations in this stem typology were smaller than the deviations in the other stems analysed due to the presence of similar thicknesses in the stems of the upper and lower zones of the plant (see Table 4). As demonstrated in Table 6, it is noteworthy that the cucumber stem experienced the most significant shrinkage or variation in diameter due to moisture loss, reaching a value of 63.71%. In contrast, the tomato exhibited the least pronounced change in diameter due to moisture loss, with a value of 16.66%. It is important to consider this aspect when utilising these fibres as additives in materials that are exposed to moisture, as it can affect the bond between the matrix and the fibre. A comparison of Tables 3 and 6 reveals a correlation between the fresh/dry stem diameter and the percentage moisture content for each stem type within the Solanaceae plant family. However, this correlation was not observed in the Cucurbitaceae plant family. This discrepancy may be attributed to the fact that, while the zucchini stem exhibited a higher percentage of moisture, its stem shrinkage when losing water was less significant than that of the cucumber. This enabled the zucchini stem to maintain its internal structure to a greater extent.