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Mature seeds of European hornbeam (Carpinus betulus L.) are characterized by deep physical and morphological dormancy. Although a procedure for their stratification is well developed, secondary dormancy prevents many healthy seeds from germinating, and this affects the productivity of the specie's nursery material. The objective of this work was to determine optimal conditions for germination of European hornbeam seeds, and how to avoid the induction of their secondary dormancy. We also aimed at establishing methods for controlling the seed germination prior to sowing. Harvested nuts were stratified in a substrate at 20°/3°C for 4 + 16–18 weeks. Following stratification, the seeds were dried up to 25, 20, 15 and 10 per cent moisture content or frozen in the substrate at −3°C for 8, 16 or 32 weeks. The seeds dried up to 10 and 15 per cent moisture content were also stored at −3°C for 8, 16 and 32 weeks. After stratification, drying, storing and freezing, the seeds were germinated at the laboratory at 20°C and 3/20°C (16 + 8 h). However, reliable germination results were only achieved when the seeds not germinating at the above listed temperatures were additionally germinated at 3°C. Poor germination at 20° and 3/20°C was due to the induction of secondary dormancy. Stratified seeds of European hornbeam were found sensitive to dehydration. Their viability decreased considerably, particularly after drying up to 10 per cent moisture content, and in the seeds dried to 15 per cent the viability further decreased during storage. The seeds that were not dried but frozen at −3°C after stratification retained their germination ability for at least 16 weeks. Our results shows dual effects of temperature on germination control of hornbeam seeds. In laboratory practice applying temperature cycles of 3°/20°C at 16/8 h intervals is recommended to avoid the induction of secondary dormancy. [ABSTRACT FROM AUTHOR]

The mating system is a central parameter of plant biology because it shapes their ecological and evolutionary properties. Therefore, determining ecological variables that influence the mating system is important for a deeper understanding of the functioning of plant populations. Here, using old concepts and recent statistical developments, we propose a new statistical tool to make inferences about ecological determinants of outcrossing in natural plant populations. The method requires codominant genotypes of seeds collected from maternal plants within different locations. Using extensive computer simulations, we demonstrated that the method is robust to the issues expected for real‐world data, including the Wahlund effect, inbreeding and genotyping errors such as allele dropout and allele misclassification. Furthermore, we showed that the estimates of ecological effects and outcrossing rates can be severely biased if genotyping errors and genetic differentiation are not treated explicitly. Application of the new method to the case study of a dioecious tree (Taxus baccata) allowed revealing that female trees that grow in lower local densities have a greater tendency towards mating with relatives. Moreover, we also demonstrated that biparental inbreeding is higher in populations that are characterized by a longer mean distance between trees and a smaller mean trunk perimeter. We found these results to agree with both the theoretical predictions and the history of English yew. [ABSTRACT FROM AUTHOR]

Quercus robur seedlings are very often infested by oak powdery mildew caused by Erysiphe alphitoides. This disease attacks primary leaves with high insolation. In our experiment seedling growth in different light conditions was observed. Seedlings were derived from intact seeds or from seeds where the distal ends of acorns were cut off. Acorns were sown in pots at four light conditions (2%, 8% and 30% light transmittance and in full sunlight). For half of the seedlings we reduced the influence of powdery mildew by using a fungicide. Height of seedlings, shoot dry mass and the degree of damage caused by Erysiphe alphitoides were measured. The highest damages were in full light conditions and the lowest in the 30% light treatment. The influence of acorn reduction on powdery mildew infection was not significant (p=0.0763), however, in the full light conditions the seedlings from cut acorns were ca. 30% less damaged. The cutting of acorns also alters the height of seedlings and shoot mass. The tallest seedlings were from cut seeds growing in the 30% light treatment. The influence of the fungicide was lowest in the 30% light treatment where the decrease in damage was only ca. 10%. For nursery practice we can say that oak seedling production from cut off acorns under 30% light transmittance should give the best results of seedling growth even without the fungicide application. [ABSTRACT FROM AUTHOR]

Shortage of water is a limiting factor for the growth and development of plants, particularly at early developmental stages. We focused on the European beech (Fagus sylvatica L.), which produces seeds and further seedlings in large intervals of up to ten years. To explore the beech seedling establishment process, six stages referring to embryo expansion were studied to determine sensitivity to dehydration. The characterization of the response of elongating embryonic axes and cotyledons included a viability test before and after dehydration and measurement of the amounts of electrolyte leakage, concentration, and arrangement of storage materials, changes in chaperone proteins related to water deficit, and accumulation of hydrogen peroxide and superoxide anion radicals. Elongating embryonic axes and cotyledons differed in water content, dehydration rates, membrane permeability before and after dehydration, protein, and lipid decomposition pattern, and amount of 44-kDa dehydrin and 22-kDa small heat shock protein (sHSP). Protruding embryonic axes were more sensitive to dehydration than cotyledons, although dehydration caused transient reinduction of three dehydrin-like proteins and sHSP synthesis, which accompany desiccation tolerance. Extended deterioration, including overproduction of hydrogen peroxide and depletion of superoxide anion radicals, was reported in dehydrated embryonic axes longer than 10 mm characterized by highly elevated cellular leakage. The apical part elongating embryonic axes consisting of the radicles was the most sensitive part of the seed to dehydration, and the root apical meristem area was the first to become inviable. The effects of severe dehydration involving ROS imbalance and reduced viability in beech seedlings with embryonic axes longer than 10 mm might help to explain the difficulties in beech seedling establishment observed in drought-affected environments. The conversion of environmental drought into climate-originated oxidative stress affecting beech seedling performance is discussed in this report. [ABSTRACT FROM AUTHOR]