RYNIK, Jakub: Effects of mycorrhization of commercial substrates on the development of spruce seedlings (Diploma thesis), Technical university in Zvolen, Faculty of Forestry, Department of Silviculture. Thesis supervisor: Doc. Ing. Ivan Repáč PhD., Zvolen LF TU, 2021, 63 p. In this thesis we focused on the assessment of the influence of growth substrates and the application of symbiotic fungi on the growth of spruce seedlings. The results after the 1st vegetation period are also briefly mentioned, but in this thesis we mainly focused on the results after the 2nd vegetation period. We applied symbiotic fungi into two substrates (Gramoflor, Agro CS) at the beginning of the experiment. These symbiotic fungi were contained in Mycorrhiza roots, Mycorrhiza soluable, in vermiculite with the fungus and in the soil taken from the forest stand. There were no symbiotic preparations in the control variant and in the pure vermiculite variant. The experiment was based with 12 variants. Each variant contained 3 replicates (3 boxes). During the 2nd growing season, the boxes were stored in the open area in Borová hora Arboretum with a minimum care (no irrigation, no fertilization), only removed weed if needed and covered with sawdust in the winter to prevent the seedlings from freezing. At the end of the growing season, we took 15 seedlings out from each box. We determined biometric quantities such as height of the above ground part of seedling, height increment, root neck thickness, weight of above ground part of dry matter of seedlings, weight of dry matter of seedling root, total dry weight of seedlings and the ratio of the weight of the root to the above ground part. On 7 seedlings out of 15 taken from each box, we examined under the magnifying glass the numbers of mycorrhotic roots and then we classified them into individual morphotypes. The measured data were evaluated with a help of a two-factor analysis of variance, which was to point out statistically significant differences. Statistically significant differences in biometric indicators were demonstrated in the weight of the above ground parts (substrates - 63.67%, inoculations - 48.29%), total weight (substrates - 59.74%, inoculations - 45.76%) in favor of the Gramoflor substrate and Mycorrhiza roots. Control variant with Agro CS substrate achieved better results with the ratio of the weight of the root to the above ground part. Substrates were found to be statistical significance for all biometric indicators. The best option for the range of mycorrhiza was a variant composed of Agro CS substrate and fungal inoculum Mycorrhiza (average at 98.45%). The representation of morphotypes was variable and in each variant was the different morphotype successful. A statistically significant difference was found in dark brown, orange-brown and white morphotype. The dark brown morphotype was the most successful in variant composed of Agro CS substrate and forest soil, orange-brown morphotype variant composed of Agro CS substrate and fungal preparation Mycorrhiza soluble and a white morphotype in a variant composed of Gramoflor substrate and vermiculite overgrown fungal inoculum. The white morphotype was not found at all for the Agro CS substrate nor with Mycorrhiza soluable.