Ovules, female gametophytes and embryos are more sensitive to heavy metal pollution than anthers and pollen of Cardaminopsis arenosa (l.) Hayek (Brassicaceae), a member of calamine flora

Reproductive processes including male and female lines, embryo and endosperm development were studied in Cardaminopsis arenosa (syn. Arabidopsis arenosa) growing on two metalliferous sites (Bukowno and Bolesław, S. Poland), rich in Zn, Pb, Cd and other metals. Disturbances of developmental processes and necroses observed in anthers and ovules influenced plant fertility and seed set of plants from both metal-polluted sites. In anthers, disturbances and necrosis during male meiosis and pollen development occurred at low frequency (4–5%). Pollen grain viability was very high, reaching over 90%. In ovules the frequency of abnormal meiosis, female gametophyte developmental disturbances and necrosis was high, 23.5–28% depending on site. The polluted environment also affected embryo and endosperm. Necrosis of whole generative structures decreased plant fertility. This study indicates that the range of disturbances and necroses in embryological structures and processes (at gametophyte level) gives a set of useful characters to determine plant tolerance to stress, complementary to many tolerance characters at the sporophyte level of plant ontogenesis

Polish geomorphological research in the Eastern Carpathians and the significance of Bieszczady National Park in the protection of inanimate nature

The paper describes Polish geomorphological research in the Eastern Carpathians mainly prior to World War II. Special attention is paid to the work of geomorphologists in the area of glacial relief recognition. The state of geomorphological research in the Bieszczady Mts was presented to a large extent in Volume 19 of the Roczniki Bieszczadzkie. Finally, the paper discusses the tradition of environmental protection in the Eastern Carpathians as well as significance of the Bieszczady National Park in the protection of inanimate nature

Climate conditions of the present-day relief development on Cape Verde Islands

Cape Verde Islands are an example of a local diversity of the semi-arid equatorial climate zone. The type and intensity of the present-day morphogenetic processes is determined mostly by total precipitation and vegetation cover. We can distinguish three types of relief development. In the warm, arid climate conditions throughout the year, volcanic forms are very slowly changed or preserved by the action of episodic water, limited to a material redeposition in the wadi channels and sand dune forming by the wind. In the semi-arid climate conditions, volcanic forms are transformed into denudationfl uvial relief in the rain period. It is visible mainly on the windward side of islands and at a lower altitude, where the weathering material is washed from slopes and carried away down the wadi channels to the sea after periodic torrential rains. At the same time on the leeward side, at a higher altitude and in agricultural areas only a small amount of material is transported over short distance

The state of the art of the studies on the Bieszczady Mts. geomorphology

The paper concerns the state of the art in research on the relief and geomorphic processes in the High and Low Bieszczady Mountains. On the basis of literature evaluation authors concluded that subsequent, detailed fieldwork is required. Furthermore additional research could supplement former opinion about development of slope and valley systems within area under considerations

Introgression of apomixis into sexual species is inhibited by mentor effects and ploidy barriers in the Ranunculus auricomus complex

Background and Aims Apomictic plants maintain functional pollen, and via pollination the genetic factors controlling apomixis can be potentially transferred to congeneric sexual populations. In contrast, the sexual individuals do not fertilize apomictic plants which produce seeds without fertilization of the egg cells. This unidirectional introgressive hybridization is expected finally to replace sexuality by apomixis and is thought to be a causal factor for the wide geographical distribution of apomictic complexes. Nevertheless, this process may be inhibited by induced selfing (mentor effects) of otherwise self-incompatible sexual individuals. Here whether mentor effects or actual cross-fertilization takes place between diploid sexual and polyploid apomictic cytotypes in the Ranunculus auricomus complex was tested via experimental crosses. ¿ Methods Diploid sexual mother plants were pollinated with tetra- and hexaploid apomictic pollen donators by hand, and the amount of well-developed seed compared with aborted seed was evaluated. The reproductive pathways were assessed in the well-developed seed via flow cytometric seed screen (FCSS). ¿ Key Results The majority of seed was aborted; the well-developed seeds have resulted from both mentor effects and cross-fertilization at very low frequencies (1.3 and 1.6% of achenes, respectively). Pollination by 4x apomictic pollen plants results more frequently in cross-fertilization, whereas pollen from 6x plants more frequently induced mentor effects. ¿Conclusions It is concluded that introgression of apomixis into sexual populations is limited by ploidy barriers in the R. auricomus complex, and to a minor extent by mentor effects. In mixed populations, sexuality cannot be replaced by apomixis because the higher fertility of sexual populations still compensates the low frequencies of potential introgression of apomixi

Synergids and filiform apparatus in the sexual and apomictic dandelions from section Palustria (Taraxacum, Asteraceae)

An evolutionary trend to reduce “unnecessary costs” associated with the sexual reproduction of their amphimictic ancestors, which may result in greater reproductive success, has been observed among the obligatory apomicts. However, in the case of the female gametophyte, knowledge about this trend in apomicts is not sufficient because most of the ultrastructural studies of the female gametophyte have dealt with amphimictic angiosperms. In this paper, we tested the hypothesis that, in contrast to amphimictic plants, synergids in apomictic embryo sacs do not form a filiform apparatus. We compared the synergid structure in two dandelions from sect. Palustria: the amphimictic diploid Taraxacum tenuifolium and the apomictic tetraploid, male-sterile Taraxacum brandenburgicum. Synergids in both species possessed a filiform apparatus. In T. brandenburgicum, both synergids persisted for a long time without any degeneration, in spite of the presence of an embryo and endosperm. We propose that the persistent synergids in apomicts may play a role in the transport of nutrients to the embryo