## 3 Results
### Morphological Studies
The results of linear correlation between micronutrient content in cucumber leaves and physical properties of the substrate indicated that there was a significant positive correlation between water holding capacity of the lignite substrate fed with standard EC medium and iron accumulation in cucumber leaves (Table 6). The coefficient of determination for this relationship was 64.06% (Table 7). There was also a significant positive correlation between zinc content in cucumber leaves and water holding capacity of lignite in the treatment with high EC of nutrient solution (Table 6), as confirmed by the significant multiple correlation coefficient R and coefficient of determination (D) of 74.21% (Table 7). \begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**Treatment**} & \multirow{2}{*}{**Physical Parameter of the Substrate**} & \multicolumn{6}{c}{**Macronutrient**} \\ \cline{3-8}  & & **N** & **P** & **K** & **Ca** & **Mg** & **S-SO\({}_{4}\)** \\ \hline \multirow{2}{*}{MW/control EC} & BD & 0.1434 & 0.7279 & 0.8977 * & \(-\)0.4575 & \(-\)0.3844 & \(-\)0.3217 \\  & WHC & 0.2534 & 0.8309 & 0.9284 * & \(-\)0.5629 & \(-\)0.4981 & \(-\)0.4277 \\ \hline \multirow{2}{*}{L/control EC} & BD & 0.0821 & \(-\)0.4286 & 0.4593 & 0.1396 & 0.0871 & \(-\)0.0737 \\  & WHC & 0.5042 & 0.1423 & 0.9115 * & \(-\)0.3581 & \(-\)0.3985 & \(-\)0.4256 \\ \hline \multirow{2}{*}{MW/high EC} & BD & 0.2919 & 0.2542 & 0.3678 & \(-\)0.3863 & \(-\)0.4751 & \(-\)0.6346 \\  & WHC & 0.3997 & 0.3472 & 0.3582 & \(-\)0.4894 & \(-\)0.5737 & \(-\)0.6828 \\ \hline \multirow{2}{*}{L/high EC} & BD & 0.5357 & 0.7794 & \(-\)0.4806 & \(-\)0.8000 * & \(-\)0.5893 & \(-\)0.6150 * \\  & WHC & 0.3990 & 0.6296 & \(-\)0.3213 & \(-\)0.6539 & \(-\)0.4329 & \(-\)0.3402 \\ \hline \end{tabular}  
* significant at \(p\leq\) 0.05.  
\end{table} 
Table 4: Linear correlation coefficient(2) for the relationship between macronutrient content in cucumber leaves and physical parameters of the medium (BD, WHC) depending on the type of medium and EC of the medium. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**Macronutrient**} & \multirow{2}{*}{**MW/Control EC**} & \multirow{2}{*}{**L/Control EC**} & \multirow{2}{*}{**MW/High EC**} & \multirow{2}{*}{**L/High EC**} \\ \cline{2-2} \cline{6-8}  & & **R** & **D (\%)** & **R** & **D (\%)** & **R** & **D (\%)** \\ \hline N & 0.4312 & 18.59 & 0.7515 & 56.48 & 0.6896 & 47.56 & 0.6417 & 41.18 \\ \hline P & 0.8648 & 74.79 & 0.6494 & 42.17 & 0.8459 & 71.55 & 0.8570 & 73.44 \\ \hline K & 0.9288 * & 86.27 & 0.9832 * & 96.67 & 0.3690 & 13.62 & 0.6479 & 41.98 \\ \hline Ca & 0.6322 & 39.97 & 0.7745 & 60.00 & 0.7345 & 53.96 & 0.8697 * & 75.64 \\ \hline Mg & 0.5953 & 35.44 & 0.8053 * & 64.85 & 0.7268 & 52.82 & 0.7167 & 51.37 \\ \hline S-SO\({}_{4}\) & 0.5279 & 27.86 & 0.7251 & 52.59 & 0.5775 & 33.35 & 0.9962 * & 99.25 \\ \hline \end{tabular}  
* significant at \(p\leq\) 0.05. D \(<\) 25%—low impact, 25-45%—average impact, 46–100%—high impact.  
\end{table} 
Table 5: Multiple correlation coefficient (R) and coefficient of determination (D) for macronutrient content in cucumber leaves vs. medium type and medium EC. The accumulation in cucumber leaves of iron, zinc and boron was significantly higher in plants grown in lignite substrate than in mineral wool regardless of the concentration of ions in the drip nutrient solution (Table S1 Supplementary Materials).