зародышевый мешок

Megaspore- and megagametophytogenesis in tobacco mutant with reduced cells number in embryo sacs were studied. It is established, that the mutation causes a disturbance of one pair of homologous chromosomes conjugation in meiosis. Consequently alongside with the haploid (24-chromosomal) spores aneuploid (23-chromosomal) spores forms which are developed into abnormal embryo sacs. At cenocyte stage of megagametophytes development falling out of 1-2 mitoses and/or their abnormal course were observed, as well as abnormalities in embryo sacs polarization.

The embryo sacs structure in the two mutant lines of Nicotiana tabacum L. was investigated. The various disturbances in the megagametopyte structure were detected. In the М-3 line the gametophyte mutation suppresses the nucleus mitotic activity and cell walls initiation in embryo sacs. These disturbances lead to the formation of low-nuclear coenocytic or cellular gametophytes. In М-2 line the cellular gametophytes with increased number of cells and nucleus was dominated. The reason of this phenomenon is an increase of mitosis number during a gametophytogenesis.

The article is focused on studying of cytoembryological preconditions of polyembryony in the not pollinated ovary of the apomictic maize line АТ-1 under in vitro and in vivo conditions. For an assessment of a nutrient medium role in polyembryony induction a relative analysis of the embryo sacs in cultivated in vitro and native plants ovaries has been lead. Dynamics of formation in them an apomictic twin proem- bryo is traced.

The research of extreme low (10°С) and high (37°С) temperatures influence under in vitro conditions on phenotypic display of three mutations in Nicotiana tabacum L. with of a certain morphological type domination was conducted. The BG-141.4 line is character- ized by low-cellular embryo sacs formation, in the SG-27/4 line the trait of the increased number of nucleus and cells in embryo sacs exhibits, the line М-3 differs by high frequency of cenocyte low- cellular embryo sacs.