Embryology ofCymbidium sinense:the Microtubule Organization of Early Embryos

Abstract

In Cymbidium sinense, the pattern of embryo development is unusual in that oblique cell divisions result in the formation of several suspensor cells prior to the development of the embryo proper. Characteristic changes in microtubular distribution can be found within the zygote and the proembryo during their development. After fertilization, the ellipsoid-shaped zygote has randomly distributed microtubules within its cytoplasm. As the zygote takes on a more rounded appearance, microtubules organize into a dense meshwork. Furthermore, microtubule bundles appear at the chalazal region of the cell prior to the first mitotic division of the zygote. At the preprophase stage of mitosis, a preprophase band of microtubules appears in the cytoplasm of the zygote. The zygote divides obliquely and unequally and gives rise to an apical cell and a slightly larger basal cell. Many randomly-aligned microtubules can be found in the cortex of the basal cell. The increase in the abundance of microtubules coincides with the isotropic expansion of the basal cell. The early division of the basal cell and subsequent division of the apical cell results in the formation of a four-celled embryo, of which three cells near the micropylar pole develop as suspensor cells. In the suspensor cells, the microtubules tend to orient in the same direction as the long axis of the cell. In addition, prominent microtubules can also be found near the adjoining cell walls of the four-celled embryo. The terminal cell is highly cytoplasmic with abundant microtubules within the cell. Subsequent divisions of the terminal cell give rise to additional suspensor cells and the embryo proper. In the mature embryo, five suspensor cells are usually present ; one eventually grows through the micropyle of the inner integument and four grow towards the chalazal pole. The cortical microtubules of suspensor cells redistribute from a longitudinal to a transverse direction as they grow towards their respective poles.# 1998 Annals of Botany Company

Suspensor Development in Gagea Lutea (L.) Ker Gawl., with Emphasis on the Cytoskeleton

“…The described configurations of the cytoskeleton probably are also involved in maintenance of the characteristic shape of the basal cell nucleus. Similar relationships have been observed in angiosperms in the endosperm (Huang et al, 1998), syncytia (Płachno et al, 2010, large polyploid cells such as the embryo suspensor Bohdanowicz, 2007, 2009;Kozieradzka-Kiszkurno et al, 2011) and endosperm haustoria Świerczyńska et al, 2013). Disturbances of radial perinuclear microtubule systems as well as increasing vacuolization of the cell were observed in older suspensor basal cells of G. lutea.…”

“…They have shown that the suspensor is actively involved in the uptake and transport of nutrients and regulators from surrounding tissues to the embryo proper, and that it is a source of signals or a mediator of signals affecting the course of embryogenesis (Yeung and Clutter, 1979;Bohdanowicz, 1987Bohdanowicz, , 2001). There is not so much published work reporting observations of the cytoplasmic skeleton in differentiating cells of embryo suspensors (Webb and Gunning, 1991;Ye et al, 1997;Huang et al, 1998;Tung et al, 2000), and only a few reports describe the cytoskeleton in highly endopolyploid embryo suspensor cells (e.g., in Alisma plantago-aquatica, Bohdanowicz, 2007, 2009;in Sedum acre, Kozieradzka-Kiszkurno et al, 2011). To understand the role of the cytoskeleton in the development of highly endopolyploid plant cells it is necessary to know the distribution of the actin and tubulin skeleton during the differentiation of these cells.…”

Alisma plantago-aquatica L.: the cytoskeleton of the suspensor development

“…It is known that cytoplasmic skeleton in plant cells plays an important role during growth and differentiation. So far, the organization of cytoskeletal components has been studied mainly during megasporogenesis and megagametogenesis [32][33][34][35][36][37]. On the other hand, little information relates to the cytoskeleton during differentiation of highly polyploid cells of embryonic suspensor.…”

Comparison of the Dislocation Density in Martensitic Steels Evaluated by Some X-ray Diffraction Methods

“…[22][23][24][25][26][27][28] The hardness, tensile stress and total elongation of the present steels are plotted against the tempering temperature in Figs. 1(a), 1(b) and 1(c), respectively.…”