Secondary metabolites are ubiquitous substances occurring naturally in trees and microorganisms. They are produced in various metabolic pathways which determine their structure and biochemical proprieties. However, the biological functions of many secondary metabolites remain undetermined. Usually, the amounts of secondary metabolites produced by trees under natural conditions are limited, which makes their mass production difficult and not cost-effective. Metabolites occurring naturally in plants, including gymnosperm and angiosperm trees, as well as in fungi, are important biologically active substances used by many industries and in modern medicine. The huge variability and potential of biological activity present in secondary metabolites make it possible to replace most of them with compounds of completely natural origin. The current breakdown of metabolites, together with the most important examples of compounds and their uses, are presented in this overview. The possibility of increasing the number of secondary metabolites in a specific environment through interaction with the most known biotic factors is discussed. The use of in vitro culture for the production of secondary metabolites and their extraction, as well as the possibility of subsequent analysis, are described. The current literature on the metabolites produced by individual species is presented.

The aim of this study was to determine the efficiency of methods for the artificial scarification of black locust seeds based on the influence of the air and liquid nitrogen temperatures. Three populations were selected for the analyses: a managed tree stand, a selected seed stand and a seed orchard. Samples of 200 seeds (4 × 50) were randomly selected. Before scarification, the seeds were stored at −70 °C for 24 h. Nine different scarification treatments were evaluated. To calculate the germination capacity and the dynamics of germination, observations were made on days 3, 5, 7, 10 and 14 after treatment. For statistical analyses, we used repeated measures analysis of variance. The obtained results indicated that the highest scarification efficiency for black locust seeds occurred in the treatment in liquid nitrogen and in an air temperature range of 85–90 °C. The provenance of seeds had a significant effect on the dynamics of germination. Thermal methods and the use of liquid nitrogen can be alternatives to the labour intensive methods of cutting the seeds or using measures that require specialised equipment.

Fraxinus excelsior L. is threatened by a variety of environmental factors causing a decline of the species. The most important biotic factors negatively affecting the condition of the F. excelsior population are fungi such as the pathogen Hymenoscyphus fraxineus. Abiotic factors with potentially harmful effect to the F. excelsior population are the accumulation of heavy metals and salinity in soils. Thus, the aim of this study was to investigate the impact of selected biotic and abiotic stress factors to determine which of them pose a threat to European ash. The study was conducted using in vitro techniques based on callus and seedlings regenerated via indirect organogenesis. Tissue cultures exclude the influence of other factors, including the environmental impact on ash extinction. The results confirmed very strong pathogenic potential of H. fraxineus in which after 14 days the callus tissue cells died as the tissue failed to activate its defense mechanisms. Experiments showed the high toxicity of cadmium in concentration of 0.027 mmol/L. Salinity caused the activity of oxidation enzymes to vary among seedlings and calluses in the control suggesting the enzymes play a role in controlling the morphogenetic development of tissue cultures.

The history and dynamics of the introduction of red oak into forest plantations in Ukraine are presented. The positive and negative consequences of this artificially introduced species are characterised. The anthropogenic factor of a broad representation of the species and the probability of low natural spread out outside the existing plantations are highlighted. The current data on the area of red oak plantations by administrative regions, forest categories, types of forest site conditions and age classes in Ukraine are indicated. The possibility of controlling and limiting the adverse invasive effects of red oak representation in forest stands is pointed out. It is recommended to conduct detailed and systematic interdisciplinary research on the degree of red oak invasiveness impact in Ukraine and effective forest care treatments for controlling its negative role.

Existing knowledge of the Ukrainian foresters related to the historical changes and current state of silver fir forests, as well as on the various methods of restoration of such forests in the Ukrainian Carpathians were discussed. Forest cover of fir stands in this region has been diminishing in the last two centuries. Only in the period from 1947 to 1956, the area of fir stands in Ukrainian Carpathians decreased by 38.8%. Currently, the restoration of fir stands in these areas are crucial for Ukrainian forestry. Therefore, the natural as well as artificial regeneration using seeds obtained from seed orchards are currently used. Thus, improving the forest stands’ conditions mostly composed of single-spruce plantations need to be improved through changing the species compositions. However, the restoration of fir stands is time and labour-intensive, and require a long-term strategy.