Ultrastructural Changes of the Mature Embryo Sac in Buckwheat (Fagopyrum esculentum) as a Result of High Temperature Exposure.

Ultrastructural Mechanisms of Aposporous Embryo Sac Initial Cell Appearance and Its Developmental Process in Gametophytic Apomicts of Guinea Grass (Panicum maximum)

“…3). The occurrence of vacuoles is normal phenomenon in megasporegenesis process (Guan and Adachi 1994), and it is also an auspice of cell degeneration (Guan and Adachi 1997) reported in Fagopyrum esculentum. The ultrastructure of dyad cells of P. maximum is comparable to that observed in other plants (Russel 1979(Russel , 1985.…”

Ultrastructural Studies of Gametophytic Apomicts in Guinea Grass (Panicum maximum) I. Differentiation of Aposporous Initial Cell

“…As first event, micropylar dyad was degenerated and chalazal dyad showed vacuoles in high degree during megasporocyte division. The occurrence of vacuoles is nor- mal phenomenon in megosporogenesis process (Guan and Adachi 1994), and it is also an auspice of cell degeneration (Guan and Adachi 1997). The ultrastructure of dyad cells of P. maximum is comparable to that observed in other plants (Russell 1979(Russell , 1985.…”

“…The ovaries were excised from florets buds, that were collected from the 2 varieties, and divided into 3 classes of 1) the stages of before and completion of megosporogenesis, 2) the appearance stage of AIC and 3) formation stage of the AIC-derived embryo sac based on an index of ovary length in different developmental stages (Chen and Kozono 1994a). The ovaries were fixed in 4% glutaradehyde and 1.5% paraformaaldehyde in 0.1 M cacodylate buffer, at pH 7.2 for 4.5 h at room temperature, and then postfixed with 1% osmium tetroxide in the same buffer at 4°C for 5 h. The fixed samples were dehydrated by a graded ethanol series and embedded in Spurr's resin (Guan and Adachi 1997). For light microscopy, sections approximately 15 mm in thickness were cut with a glass knife on a microtome and stained with toluidine blue.…”

Ultrastructural Studies of Gametophytic Apomicts in Guinea Grass (Panicum maximum) II. Characteristics of Aposporous Initial Cell-derived Embryo Sac

“…The plants were grown in greenhouse in University of Miyazaki. The ovaries were excised from floret buds, and fixed in 4% glutaradehyde and 1.5% paraformaldehyde in 0.1 M cacodylate buffer, at pH 7.2 for 4.5 h at room temperature, and then postfixed with 1% osmium tetroxide in the same buffer at 4°C for 5 h. The fixed samples were dehydrated by a graded ethanol series and embedded in Spurr's resin (Guan and Adachi 1997). For light microscopy, sections approximately 15 mm in thickness were cut with a glass knife on a microtome and stained with toluidine blue.…”

“…They indicated that AIC usually differentiate adjacent to degenerating tetrad, and megaspores or one-nucleated sexual embryo sacs. To clarify the time of degeneration of sexual ones and appearance of apomictic ones (AIC), Guan et al (2006) reported that the degeneration is a continuant process, from as early as megaspore mother cell (MMC), dyad, tetrad, to formation of megaspore and one-nucleate embryo sac, and accompanying with the degeneration, AIC appears.…”