## 3 Results and Discussion
### Biometric Parameters of Seedlings  
The biometric parameters of the studied _Brassica_ seedlings are presented in Table 2 and Figure 2. During the growing season, the SPAD index was highest in broccoli grown on substrate PRO2 (52.5), and lowest in white cabbage grown on the standard (control) substrate (38.1). SPAD values were significantly influenced by the applied substrate, but species-specific differences were observed. SPAD values were significantly higher in broccoli grown on PRO1 (by approx. 24%) and PRO2 (by approx. 27%) than on the control substrate. In white cabbage leaves, SPAD values were significantly higher on all three used in the experiment substrates (by approx. 10% on PRO1, by approx. 41% on PRO2, and by approx. 25% on PRO3). The analyzed substrates had the lowest effect on SPAD values in cauliflower seedlings. SPAD values were significantly lower in cauliflowers grown on substrate PRO1 (by approx. 8%) than in the control treatment. According to [PERSON] et al. [24], the chlorophyll content of leaves decreases with a drop in nutrient concentrations in the substrate. Similar results were obtained by [PERSON] et al. [25]. Studies have shown that paper waste substrates \(\geq\)30% decreased dental conductance, while chlorophyll fluorescence and content of chlorophylls decreased with a high PW ratio, negatively affecting the plant physiology. The substrates exert a positive influence on plant height. Plants grown on substrates used in the experiment were shorter and had a compact growth habit, which is highly desirable in seedling production. The greatest differences in plant height relative to the control treatment were observed in broccoli (approx. 39%) and cauliflowers (approx. 38%) grown on PRO1, and in white cabbage (approx. 35%) grown on PRO2. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Factor** & **SPAD** & **Plant Height** & **Number of Leaves** & **Leaf Mass** & **Root Mass** \\ \hline Substrate (A) & \textless{}0.001 & \textless{}0.001 & 0.422 & 0.159 & 0.156 \\ Species (B) & 0.117 & 0.056 & 0.017 & \textless{}0.001 & \textless{}0.001 \\ Interaction (A \(\times\) B) & \textless{}0.001 & \textless{}0.001 & 0.107 & \textless{}0.001 & \textless{}0.001 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: \(p\)-value in ANOVA of the biometric parameters of seedlings of the analyzed _Brassica_ species. According to [PERSON] et al. [26], vegetables, including cabbage, have a high demand for potassium which promotes carbohydrate synthesis and translocation, increases water-use efficiency, regulates nitrogen metabolism, and improves seedling quality [27]. [PERSON] et al. [28] observed that nitrogen is one of the key nutrients in crop production that promotes seedling germination and increases leaf surface area. In the work of [PERSON] et al. [26], macronutrients were arranged in the following order based on their uptake levels: K \(>\) N \(>\) Ca \(>\) S \(>\) P \(>\) Mg. In the present study, nutrient concentrations were highest in the control substrate (Table 1), which could explain why control treatment plants were taller than the plants grown on substrates used in the experiment. After six weeks, _Brassica_ plants had an average of three to five leaves (Table 2). The number of leaves was not affected by the type of substrate, and minor differences in this parameter were observed between species. The smallest number of leaves was noted in broccoli seedlings grown on PRO1, and the highest number of leaves was noted in broccoli  
Figure 2: The influence of the tested substrates on the biometric parameters of seedlings of the analyzed _Brassica_ species: a–h–various letters denote significant differences at \(p\) < 0.05 (Tukey’s test). grown on the control substrate, and in white cabbage grown on the control substrate and PRO3. Leaf mass was associated with _Brassica_ species, and it was also influenced by the interaction effects of substrate and species.