| dc.description.abstract | As shown by the results of our redearch, meiosis in the cells of sporogenous anthers and ovules of the diploid
forms of S. Vavilovii generally follows a regular course; which leads up to the formation of spores with a strictly
haploid number of chromosomes, n = 7. Out of the 150 examined specimens, only three showed some slight meiotic
disturbances. Accordingly, the development of the male and female gametophytes of the diploids was also regular: it
was achieved by means of three-nuclear, vital pollen seeds and eight-nuclear, polarized ovular pouches. These
organisms multiply in a sexual manner, their characteristic feature being a double fertilization of the ovular
pouch, while the bud seed and the endosperm develop simultaneously.
In the first prophase of the meiotic division of tetraploids apart from the variable number ot bivalents we have
found also univalents and higher-order chromosome configurations. This type of chromosome coniugation usually led
up to their uneven division, and then to the formation of spores with an un-strictly haploid number of chromosomes.
The male gametophyte of teraploids in most caess develops from microspores with the number or chromosomes n = 14;
it is suspected, however, that some of the pollen seeds develop from microspores with different chromosome numbers.
On the other hand, the female gametophyte develops only frOm macrospores wih chromosome number n = 14. The nearly
40 per cent degeneration of embryos and endosperm is connected with the irregular numbers of chromosomes introduced
into the zygote through the intermedaiary of male gametes. | en_EN |
