Female sporogenesis in the native Antarctic grass Deschampsia antarctica Desv.

Abstract

Abstract:The development of megasporocytes and the functional megaspore formation in Deschampsia antarctica were analyzed with the use of microscopic methods. A single archesporial cell was formed directly under the epidermis in the micropylar region of the ovule without producing a parietal cell. In successive stages of development, the meiocyte was transformed into a megaspore tetrad after meiosis. Most megaspores were arranged in a linear fashion, but some tetrads were T-shaped. Only one of the 60 analyzed ovules contained a cell in the direct proximity of the megasporocyte, which could be an aposporous initial. Most of the evaluated D. antarctica ovules featured monosporic embryo sacs of the Polygonum type. Approximately 30% of ovules contained numerous megaspores that were enlarged. The megaspores were located at chalazal and micropylar poles, and some ovules featured two megaspores -terminal and medial -in the chalazal region, or even three megaspores at the chalazal pole. In those cases, the micropylar megaspore was significantly smaller than the remaining megaspores, and it did not have the characteristic features of functional megaspores. Meiocytes and megaspores of D. antarctica contained polysaccharides that were detectable by PAS-reaction and aniline blue staining. Starch granules and cell walls of megasporocytes, megaspores and nucellar cells were PAS-positive. Fluorescent callose deposits were identified in the micropylar end of the megasporocytes. During meiosis and after its completion, thick callose deposits were also visible in the periclinal walls and in a small amount in the anticlinal walls of megaspores forming linear and T-shaped tetrads. Callose deposits fluorescence was not observed in the walls of the nucellar cells.

Polish Polar Research

“…During the development of the ovule, two integuments made up of two layers of cells undergo differentiation, which was shown in C. apetalus analyzed in this paper, as well as in C. quitensis and Cerastium alpinum L. (Giełwanowska 2005;Kellmann-Sopyła et al 2017). A monosporic embryo sac of the Polygonum type differentiated in the ovule (Bednara 2003;Giełwanowska 2005;Domaciuk et al 2016). This type of development is most common in flowering plants -it affects about 95% of flowering plant species (Bednara 2003).…”