The development of oat endosperm is modified by chromatin and nuclei elimination, intrusive growth of cell walls, and polyploidisation of cell clones. The last event is correlated with somatic crossing-over.

This study analysed cytogenetic events occurring in the syncytial endosperm of theAvena magnaH. C. Murphy & Terrell × Avena longiglumisDurieu amphiploid, which is a product of two wild species having different genomes. Selection through the elimination of chromosomes and their fragments, including those translocated, decreased the level of ploidy in the endosperm below the expected 3n, leading to the modal number close to 2n. During intergenomic translocations, fragments of the heterochromatin-rich C-genome were transferred to the D and Al genomes. Terminal and non-reciprocal exchanges dominated, whereas other types of translocations, including microexchanges, were less common. Using two probes and by counterstaining with DAPI, theA. longiglumisand the rare exchanges between the D and Al genomes were detected by GISH. The large discontinuity in the probe labelling in the C chromosomes demonstrated inequality in the distribution of repetitive sequences along the chromosome and probable intragenomic rearrangements. In the nucleus, the spatial arrangement of genomes was non-random and showed a sectorial-concentric pattern, which can vary during the cell cycle, especially in the less stable tissue like the hybrid endosperm.

In the present work, numerous species of useful and wild plants were identified in the archaeobotanical samples (moat deposit and two ceramic jugs) collected from the mediaeval locality of the Kolno Castle, near Brzeg, south-western Poland. At the confluence of two rivers, in the vicinity of the castle, it was possible to cultivate cereals on poor alluvial soil, in the ground with a layer of ferruginous concretions. The characteristic weeds of the classes Secalinetea and Chenopodietea indicated the cultivation of winter cereals and garden plants. Polymorphic populations of millet were cultivated. Apart from the annual plants, the following fruit trees were grown: plums, peaches and walnuts. Fruits of many wild species were also gathered for consumption. Correlation analysis of the characters ofPrunusL. stones proved that the development of the organ is conservative. Morphometric analysis of the plum stones showed that in addition to the specimens belonging to the speciesPrunus spinosaL. andPrunus domesticaL./Prunus insititiaL., there were hybrids between these two species. Multivariate analyses evidenced that the complexes of cultivated and wild plums and cherries can form hybrid syngameons revealing continuous variation and non-random structure. The variability of filbert nuts corresponded to the variability of a large modern population of this species that is composed of many genetically different morphotypes. Variabilities of inter-specific units of fossil and contemporary forms belonging to various taxa were described by ellipsoids of various shapes and arrangements in the three-dimensional ordination space.

The basis of any patterns of variation in plant populations is the breeding system they express. In the genus Brachypodium, the breeding system ranges from autogamy in facultatively chasmogamic Brachypodium distachyon to allogamy in obligatory chasmogamic B. pinnatum. B. distachyon and B. sylvaticum appeared to be extremes with respect to dormancy and germination behaviour. Winter and facultatively biennial forms of the annual B. distachyon expressed an intermediate dormancy behaviour towards perennial species. Perennial species such as B. pinnatum, B. phoenicoides, B. rupestre and B. sylvaticum demonstrated allogamic behaviour and were highly dormant. The storage potential of hemicelluloses in endosperm cell walls and suberin-phenolic synthesis in testa and pigment strand differ distinctly between annuals and perennials. The suberized glumellae base and caryopsis attachment restrict the growth of coleorhiza and can change growth relationships between root and coleoptile. Coleorhizal hairs facilitating water capillary adhesion to an embryo are developed in both types of Brachypodium species, but in perennial types they are less efficient. The pattern of development of coleorhizal hairs distinguishes Brachypodium species from members of the tribe Triticeae. The coleorhizal hairs are less developed in Triticeae. This trait is variable at the populational level, especially in heterozygous populations (B. phoenicoides). Both extremes in terms of dormancy, i.e. B. distachyon and B. sylvaticum, revealed inter- and intrapopulational variability of germination.