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The collective species Hieracium pilosella L. is represented in Poland by two cytotypes: the tetraploid (2n = 36) and pentaploid (2n = 45). A comparative embryological analysis of these two cytotypes showed, that tetraploid cytotype has a normal sporogenesis and sexual mode of reproduction. In the pentaploid cytotype the florets of unopened capitula were examined. Sporogenesis both in anthers and in ovules is highly disturbed. In rare cases the meiotic fully organized embryo sacs were formed. As a rule aposporic embryo sacs arising from somatic cells of chalaza or from nucellar epidermis were present. In still unopened capitula the development of embryos arising parthenogenetically preceded that of endosperm formed in the autonomous way. The occurrence of developmental abnormalities (multiply embryo sacs, polyembryony, adventitious integumental embryony) have been observed in ovules of the pentaploid cytotype.
The metabolites in the ovule come from the receptacle, ovary wall and placenta. They are accumulated in the chalaza and then translocated in reproductive and somatic structures via a system of specialized tissues. The hypostase is of great importance because it lies at the boundary of the chalaza with the nucellus and integuments, and contacts the vascular bundle. In the megagametophyte, the cell walls, which have many outgrowths, receive metabolites from the hypostase via podium and postament tissues. Histochemical data on accumulation of proteins, polysaccharides, lignin and tannins in tissues during ovule and seed development are presented. The dynamics of these substances and the character of metabolism in tissues are suggested as indicators of metabolite flow.
Ovule and seed morphogenesis in Vaccinium myrtillus was studied here for the first time. The gynaeceum is paracarpous. The ovules are developed at sutural-angular placentae. Periclinal divisions of the subepidermal cells of the placenta usually precede formation of the ovular primordia. The ovules are ana-campylotropous, medionucellate, unitegmic, leptochalazal and sessile. The initials and dynamics of different ovule structures were determined. The chalazal zone of the nucellus transforms into the postamento-podium. The integument is of dermal origin, with a typical endothelium. The ovule has a hypostase, which is initiated with the beginning of ovular primordium differentiation. It is cup-shaped in the mature ovule and consists of 2-3 layers. Their cell walls are not lignified. The nucellus, integumental parenchyma, endothelium and hypostase do not persist in the mature seed. The latter is exotestal. The embryo sac develops according to the Polygonum type. The endosperm is cellular, with micropylar and chalazal haustoria. The mature embryo is large and well differentiated into organs.
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