Plants from Tatra mountain population
Developmental processes in the male and female lineages proceeded, in a high percentage, regularly. Three-celled mature pollen developing in tetrasporangiate anthers from microsporocytes after meiosis and simultaneous cytokinesis was highly viable, reaching 98% of the viability (Tab. 1; Fig. 1a, b). In the ovary two campylotropous, tenuicellular and bitegnic ovules underwent simultaneous development. In 95% of analyzed ovules the archesporial cell in the nucellus develops in the megasporocyte and linear tetrad forms after meiotic divisions (Fig. 1c-e). T-shaped tetrads were also observed. Monosporic female gametophyte (embryo sac) develops from the chalazal megaspore according to the Polygonum type (Fig. 1e). In mature 7-celled embryo sac at the micropylar region an egg apparatus with egg cell and two synergids is located, in central cell secondary nucleus is forming after fusion of two polar nuclei, at chalazal pole three short-living antipodals (Fig. 1f). After fertilization the embryo develops according to the Onagrad type and whole endosperm is consumed during embryogenesis (Fig. 1g). In ca 8% of young ovules additional embryo sac underwent development (Tab. 2). It might originated from additional archesporial cell or rather from the developing sub-chalazal megaspore of the same tetrad (Fig. 1h). These additional embryo sacs can reach maturity (Fig. 1i). The most frequently additional, sub-chalazal originated embryo sacs were observed at early stage of development.
Degenerations during megasporogenesis, embryo sac development and in mature embryo sac occurred with low frequency (7%) in analyzed flower buds. Shortening of mature embryo sacs were found in 4% of ovules, aging of mature embryo sacs without fertilization and lack of embryo sac in 7% of ovules, disturbed embryogenesis in 5% of seeds. Degenerations of whole flower buds and whole ovules both in flowers and developing seeds were observed with frequency of 7% (Tab. 2).
In 41% of analyzed fruits 2-seeds were formed, in 21% only one-seed developed, 38% fruits had no seeds.