## 3 Impact of _Quercus_ Species Diversity on Acorn Morphological and Chemical Characteristics  
The wide range of occurrences worldwide and the multiplicity of species influence the varied distribution of _Quercus_ species by region (Figure 3). Individual species exhibit significant morphological variability in leaf structure, the structure (Figure 4), and the chemical composition of acorns (Table 1). Factors affecting oaks and acorns' morphological and chemical composition include genetic variation due to species differences and environmental factors, including primarily climatic conditions, adaptive processes, and interdependence with other species and microorganisms [20; 32; 33]. Among the characteristics that distinguish acorns of different _Quercus_ species are bowl structure, shape, weight (along with the percentage of hardened pericarp), and dimensions (length and diameter) [6; 34]. The literature data show that the predominant component of acorns is carbohydrates, among them starch. The variation of starch content in acorns is very high, ranging from 22.03 to 68.15 g/100 g d.m., indicating the degree of maturity of the acorns, as demonstrated in a study by [PERSON] et al. [42]. [PERSON] and [PERSON] [43] reported that acorn starch is characterized by an amylose content in the range of 15-39%, and the size of  
Figure 3: The diversity of oak trees worldwide is shown in the example of selected countries with growing interest in oak cultivation. Source: own elaboration based on [PERSON] et al. [30]. starch granules fluctuates between 2 and 24 \(\upmu\)m. The proportion of resistant starch is also significant, at 41.4% [43]. Depending on the species, acorns contain from 1.05 to 14.95% fat. In addition to species differences, the fat content can also be affected by origin and related environmental factors, which significantly alter the fat content of the acorns of the species _Q.__ilex_[46]. In the case of fatty acid composition, [PERSON] et al. [47] in acorns of _Q.__ilex_ and _Q.__super_ species, [PERSON] et al. [48] in acorns of _Q.__rotundifolia_ species, and [PERSON] et al. [49] in acorns of _Q.__ilex_ and _Q.__cocifera_ species showed that the predominant fatty acid was oleic acid, the \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{_Quercus_ **Species**} & \multicolumn{5}{c}{**Chemical Components**} & \multirow{2}{*}{**References**} \\ \cline{2-2} \cline{4-6}  & **Fat** & & **Protein** & & **Carbohydrates** & **Starch** & **Ash** \\ \hline _Q.__brantii_ & 0.72 & 3.37 & n.d. & 63.00 & 2.09 & [44] \\ _Q.__alliprinos_ & 2.31 & 4.94 & 77.86 & n.d. & 1.78 & [45] \\ _Q.__erris_ & 1.05 & 4.3 & n.d. & 64.55 & 1.75 & [44] \\ _Q.__cocifera_ & 2.67 & 2.54 & n.d. & 66.2 & 1.81 & [44] \\ _Q.__ilex_ & 9.14–14.95 & 3.90–5.94 & 8.95–12.47 * & n.d. & 1.34–2.02 & [46] \\ _Q.__i.__intercaria_ & 1.55 & 4.37 & n.d. & 68.15 & 1.95 & [44] \\ _Q.__ithaburensis_ & 0.76 & 2.84 & 58.94 & n.d. & 3.21 & [45] \\ _Q.__rotundifolia_ & 8.38–13.51 & 3.56–4.34 & n.d. & 47.98–59.95 & 1.94–2.19 & [42] \\ _Q.__super_ & 2.09–8.22 & 6.19–9.38 & n.d. & 22.03–60.00 & 2.12–2.98 & [42,44] \\ \hline \hline \end{tabular}  
* sugar content; n.d.—no data.  
\end{table} 
Table 1: Basic chemical composition of acorns of different _Quercus_ species. Figure 4: Morphological differences in leaves and acorns of different _Quercus_ species. Source: own elaboration based on available images [35; 36; 37; 38; 39; 40; 41]. share of which was about 50-60% of total fatty acids. In contrast, a study by [PERSON] [50] reported that the percentage of oleic acid was similar to or lower than that of linoleic acid in the acorns of species classified into the _Quercus_ taxonomic section, while in the acorns of species in the _Cerrus_ section, the predominant oleic acid remained, with a maximum share of 54.3% in the acorns of species of _Q. branttii_. Regardless of the proportion of individual fatty acids, it was confirmed that in the oil of the acorns, unsaturated fatty acids are the dominant group [47; 48; 50].