Pollen and achene characters of natural interspecific hybrid Solidago ×niederederi Khek were analyzed and compared with putative parental species S. virgaurea L. and S. canadensis L. to estimate the level of disturbances in generative reproduction resulting from its hybrid nature. Pollen viability (stainability) of Solidago ×niederederi from one newly discovered locality in NE Poland was evidently reduced to ~65% in both viability tests (acetocarmine and Alexander). The diameter of viable pollen (median 21.11 µm) fell between S. canadensis (median 19.52 µm) and S. virgaurea (median 23.48 µm). Both parental species produced normally developed achenes with high frequency (~90%) whereas in the hybrid, the seed set was dramatically low (6%). The results clearly indicated that sexual reproduction of hybridogenous taxon S. ×niederederi is disturbed, and its potential impact as an invasive species depends mainly on vegetative propagation.

Plants are exposed to various stress factors which might lead to structural damage and physiological function abnormalities. Drought is one of the environmental stress factors that reduce the productivity of plants. The aim of our study was to determine the influence of drought stress induced by mannitol (-0.5 and -1.5MPa) on selected physiological processes in Z. mays L. In the first stage we studied the effect of mannitol on the germination. In the second stage the effect of mannitol on the growth of plants germinated on distilled water and watered with mannitol in growth phase were measured. Mannitol, which decreased the water content in a concentration-dependent manner, had an inhibitory effect on germination and growth of seedlings and adult plants. Electrolyte leakage of cell membranes of the Z. mays seedlings showed high disturbances in the functioning of the membrane structures in the osmotic drought conditions. Similar results were obtained for maize roots, shoots and leaves in both treatment studies. Chlorophyll content showed only significant differences in plants from treated during the growth phase. Drought stress caused a decrease in chlorophyll content by almost a half compared to the control plants. Measurements of chlorophyll fluorescence of plant leaves from the second stage of experiments showed changes in fluorescence activity parameters Fv/Fm, NPQ, Rfd, qP, ect.; gas exchange measurements also showed changes in activity in each of the two phases.

The Viola epipsila-V. palustris complex is a highly taxonomically complicated group of species in its entire circumboreal range of distribution. Habitat loss, forest flooding, and hybridization could lead to the extinction of V. epipsila. A hybrid index and principal component analysis (PCA) were used to select qualitative and quantitative morphological features to distinguish parent species and hybrids, inter simple sequence repeat (ISSR) markers to determine the genetic diversity of the populations, flow cytometry to estimate the genome size (GS), and non-coding chloroplast DNA (cpDNA) regions to indicate the directions of crosses. All taxa are very morphologically variable, and their features can change within a season. The most stable feature is the distance of the bracts on the pedicel from the rhizome. The genetic diversity of all taxa populations is low and highly influenced by selfing and vegetative propagation. The population structure is differentiated: populations of V. epipsila or V. palustris, mixed populations with both parent species, F1 hybrids and populations with introgressive forms occur in different regions. The interspecific GS variation corresponds to the ploidy level (4x = 2.52 pg, 8x = 4.26 pg, 6x = 3.42 pg). Viola epipsila is the mother plant of the hybrids. Research has shown the risk of V. epipsila extinction in Central Europe and the importance of local populations in studying the role of hybridization in reducing/maintaining/increasing biodiversity.