Early Stages in the Development of Wheat Endosperm. I. The Change From Free Nuclear to Cellular Endosperm

1975 ◽  
Vol 23 (2) ◽  
pp. 311 ◽  
Author(s):  
DJ Mares ◽  
K Norstog ◽  
BA Stone
Keyword(s):  
Mitotic Spindle ◽  
Endosperm Development ◽  
Wall Material ◽  
Ventral Region ◽  
Wheat Endosperm ◽  
Cellular Endosperm ◽  
Dorsal Area ◽  
Cytological Features ◽  
Ventral Area ◽  
Days After Anthesis

The cytological features of the cellularization of the free nuclear endosperm of wheat are described. Following the initial proliferation of nuclei the endosperm is divided into a small ventral area and a larger dorsal area which then develop separately. Cell wall formation in both regions is independent of a mitotic spindle and appears to be mediated by freely growing walls. Wall material is laid down along lines already marked out by ingrowth from the plasma membrane into the central cell cyto- plasm. By the time that cellularization is complete the smaller ventral region has been transformed into a layer of small, thick-walled cells whilst the larger dorsal area contains large, highly vacuolate endosperm cells. A model is proposed which endeavours to link the morphological features observed in embryo sacs, collected from wheat ovules 2-6 days after anthesis, into an ontogenetic sequence. This model is compared with previously published descriptions of wheat endosperm development.

Early Stages in the Development of Wheat Endosperm. II. Ultrastructural Observations on Cell Wall Formation

1977 ◽  
Vol 25 (6) ◽  
pp. 599 ◽  
Author(s):  
DJ Mares ◽  
BA Stone ◽  
C Jeffrey ◽  
K Norstog
Keyword(s):  
Cell Wall ◽  
Thin Layer ◽  
Embryo Sac ◽  
Central Cell ◽  
Wall Material ◽  
Cross Wall ◽  
Wheat Embryo ◽  
Wheat Endosperm ◽  
Early Stages ◽  
Cellular Endosperm

In the first 4-5 days after anthesis, the central cell of the wheat embryo sac undergoes transformation from a multinucleate syncytium to the cellular endosperm. This is accomplished initially by the centripetal growth of wall projections from the central cell wall and the formation of cylindrical, highly vacuolate alveoli. Growth is mediated through the production and planar aggregation of vesicles at the distal tip of the developing projections. The innermost ends of the alveoli are closed by a thin layer of cytoplasm which is bounded on the inner side by the vacuolar membrane of the central cell. Cell wall material is not found in this thin layer of cytoplasm and the alveoli therefore are not complete cells. Following the division of the alveolar nucleus a cross-wall is laid down between the daughter nuclei by a process which is similar to normal cytokinesis and a layer of endosperm cells is formed from the peripheral portions of the alveoli. This pattern of centripetal growth of alveoli and the formation of complete cells from the proximal portions continues until cellularization is completed by the confluence of alveoli originating from opposite sides of the central cell. Further growth of the cellular endosperm is accomplished by the meristematic activity of the peripheral layer of cells. The ultrastructure of the early stages of partitioning of the central cell is discussed in relation to current views on the ontogeny of wheat endosperm.

Microtubular configurations during endosperm development in Phaseolus vulgaris

1994 ◽  
Vol 72 (10) ◽  
pp. 1489-1495 ◽  
Author(s):  
X. XuHan ◽  
A. A. M. Van Lammeren
Keyword(s):  
Electron Microscopy ◽  
Cell Wall ◽  
Phaseolus Vulgaris ◽  
Key Words ◽  
Cell Walls ◽  
Endosperm Development ◽  
Initial Cell ◽  
Related Cell ◽  
Cellular Endosperm ◽  
Cell Shaping

Microtubular cytoskeletons in nuclear, alveolar, and cellular endosperm of bean (Phaseolus vulgaris) were analyzed immunocytochemically and by electron microscopy to reveal their function during cellularization. Nuclear endosperm showed a fine network of microtubules between the wide-spaced nuclei observed towards the chalazal pole. Near the embryo, where nuclei were densely packed, bundles of microtubules radiated from nuclei. They were formed just before alveolus formation and functioned in spacing nuclei and in forming internuclear, phragmoplast-like structures that gave rise to nonmitosis-related cell plates. During alveolus formation cell plates extended and fused with other newly formed walls, thus forming the walls of alveoli. Growing wall edges of cell plates exhibited arrays of microtubules perpendicular to the plane of the wall, initially. When two growing walls were about to fuse, microtubules of both walls interacted, and because of the interaction of microtubules, the cell walls changed their position. When a growing wall was about to fuse with an already existing wall, such interactions between microtubules were not observed. It is therefore concluded that interactions of microtubules of fusing walls influence shape and position of walls. Thus microtubules control the dynamics of cell wall positioning and initial cell shaping. Key words: cell wall, cellularization, endosperm, microtubule, Phaseolus vulgaris.

Arabinoxylan and (1→3),(1→4)-β-glucan deposition in cell walls during wheat endosperm development

Planta ◽  
2006 ◽  
Vol 224 (2) ◽  
pp. 449-461 ◽  
Author(s):  
Sully Philippe ◽  
Luc Saulnier ◽  
Fabienne Guillon
Keyword(s):  
Cell Walls ◽  
Endosperm Development ◽  
Wheat Endosperm

Factors Regulating the Accumulation of Starch in Ripening Wheat Grain

1975 ◽  
Vol 2 (3) ◽  
pp. 311 ◽  
Author(s):  
CF Jenner ◽  
AJ Rathjen
Keyword(s):  
Free Space ◽  
Radioactive Material ◽  
Wheat Grain ◽  
Wheat Endosperm ◽  
Insoluble Material ◽  
Days After Anthesis

Estimates of the faculty of wheat endosperm to convert sucrose to starch were obtained by incubating dissected endosperm in solutions of [14C]sucrose and then measuring the absorption of [14C]sucrose and the amounts of 14C accumulating as insoluble material. Samples of grain were taken from plants growing in the field at each of four stages of maturity: at 17 days after anthesis, just after the synthesis of starch had begun; at 28 days when the grains were about half-grown; at 38 days when the accumulation of starch had slowed down and almost ceased; and at 49 days when the grains were fully grown. More [14C]sugar entered the free space of the endosperm of 49- than of 28-day-old grain, and more sucrose was absorbed by the endosperm cells of the older grain. Endosperm taken from grains sampled at 28 days produced more insoluble radioactive material (mostly starch) than grains sampled at any other stage, and compared to 28-day grain, grain sampled at 38 days produced less than one-third of the quantity of [14C]starch. At each stage, the amounts of sucrose in the free space and in the cells of the endosperm were determined on comparable samples of grain developing normally in the field. There was significantly more sucrose on day 38 than on day 28, both in the free space and in the cells of the endosperm. It is concluded that the onset of the declining phase of accumulation of starch, as the grains begin to ripen, is due to a fall in the capacity of the grains to synthesize starch, and is not attributable to postulated reductions in the supply of assimilate to ripening grain.

The development of the embryo sac of sunflower Helianthus annuus after fertilization

1973 ◽  
Vol 51 (5) ◽  
pp. 879-890 ◽  
Author(s):  
William Newcomb
Keyword(s):  
Helianthus Annuus ◽  
Mitotic Spindle ◽  
Embryo Sac ◽  
Endosperm Development ◽  
Primary Endosperm Nucleus ◽  
Single Row ◽  
Wall Formation ◽  
Globular Stage ◽  
Spindle Apparatus ◽  
Single Fertilization

The degeneration of one synergid denotes the initiation of embryo and endosperm development in the embryo sac of sunflower Helianthus annuus L. The other synergid, the persistent synergid, is present until the late globular stage of embryogenesis. The primary endosperm nucleus divides before the zygote nucleus forming a coenocytic nuclear endosperm. When about eight endosperm nuclei are present during the early globular stage of embryogenesis, endosperm wall formation starts at the micropylar end of the embryo sac. The walls continue to grow toward the chalazal end of the embryo sac apparently as a result of the activity of Golgi located at the tips of the growing walls. Most endosperm wall formation is not associated with a mitotic spindle apparatus in sunflower. The suspensor of the embryo consists of a large basal cell during the proembryo stages, a single row of cells during the early globular stages, and at the late globular stage a double tier of cells near the radicle end of the embryo and a single row at the micropylar end of the embryo sac. Occasionally embryo development occurs in the absence of endosperm when only single fertilization has taken place. The development and nutritional implications of post-fertilization events in the sunflower embryo sac are discussed.

scholarly journals Functionally defined white matter of the macaque monkey brain reveals a dorso-ventral attention network

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Ilaria Sani ◽  
Brent C McPherson ◽  
Heiko Stemmann ◽  
Franco Pestilli ◽  
Winrich A Freiwald
Keyword(s):  
Attentional Control ◽  
Diffusion Mri ◽  
Ex Vivo ◽  
Temporal Cortex ◽  
Macaque Monkey ◽  
Control Area ◽  
Endogenous Attention ◽  
Ventral Region ◽  
Classical Studies ◽  
Dorsal Area

Classical studies of attention have identified areas of parietal and frontal cortex as sources of attentional control. Recently, a ventral region in the macaque temporal cortex, the posterior infero-temporal dorsal area PITd, has been suggested as a third attentional control area. This raises the question of whether and how spatially distant areas coordinate a joint focus of attention. Here we tested the hypothesis that parieto-frontal attention areas and PITd are directly interconnected. By combining functional MRI with ex-vivo high-resolution diffusion MRI, we found that PITd and dorsal attention areas are all directly connected through three specific fascicles. These results ascribe a new function, the communication of attention signals, to two known fiber-bundles, highlight the importance of vertical interactions across the two visual streams, and imply that the control of endogenous attention, hitherto thought to reside in macaque dorsal cortical areas, is exerted by a dorso-ventral network.

Morphology of the Crease Region in Relation to Assimilate Uptake and Water Loss During Caryopsis Development in Barley and Wheat

1983 ◽  
Vol 10 (6) ◽  
pp. 473 ◽  
Author(s):  
MP Cochrane
Keyword(s):  
Water Loss ◽  
Grain Filling ◽  
Wall Material ◽  
Wall Structure ◽  
Primary Wall ◽  
Xylem Parenchyma ◽  
Filling Water ◽  
Phenolic Substances ◽  
Electron Lucent ◽  
Days After Anthesis

Changes take place about 35 'days' after anthesis in the wall structure of the chalazal cells in caryopses of barley cv. Midas and wheat cv. Sicco grown in conditions where the number of 'days' from anthesis to harvest-ripeness is 60. The primary wall becomes lignified and is separated from the symplast by a layer of suberin. Massive deposits of electron-lucent wall material are laid down between the primary wall and the plasma membrane. From 15 'days' after anthesis increasing amounts of phenolic substances are found in the chalazal cell contents. Xylem parenchyma cells in the crease have some of the characteristics of gland cells and it is suggested that they may function in the control of the water content of the endospem. The cell wall modifications in the chalaza are interpreted as providing a means whereby, during the later stages of grain-filling, water loss from the endosperm can take place without interrupting the supply of assimilates to starchy endospem cells.

Cellular endosperm formation in Phaseolus vulgaris. I. Light and scanning electron microscopy

1988 ◽  
Vol 66 (6) ◽  
pp. 1209-1216 ◽  
Author(s):  
Edward C. Yeung ◽  
Michael J. Cavey
Keyword(s):  
Phaseolus Vulgaris ◽  
Mitotic Activity ◽  
Endosperm Development ◽  
Bean Seed ◽  
Phaseolus Vulgaris L ◽  
Entire Surface ◽  
Cotyledon Stage ◽  
Cellular Endosperm ◽  
Inner Surface ◽  
Endosperm Formation

The formation of the endosperm in Phaseolus vulgaris L. conforms to the nuclear pattern of endosperm development. The endosperm is partially cellularized in the vicinity of the developing embryo, while the rest of the endosperm remains multinucleate. Mitotic activity of the endosperm is gradually confined to the region adjacent to the tips of the enlarging cotyledons. Continuing mitotic activity in this region results in the formation of cellular endosperm in the bean seed. At the cotyledon stage of embryo development, except in the region of the degenerating nucellus, the entire surface of the developing embryo is covered by a layer of cellular endosperm cells. Initially, the cellular endosperm is loosely attached to the inner surface of the seed coat. With the disappearance of the liquid endosperm, it becomes firmly attached. Further expansion of the seed results in the separation of cellular endosperm cells along their long axes. As the seed matures, the cellular endosperm dries, with no apparent degradation of its cells.

Synthesis and degradation of proteins during wheat endosperm development

1976 ◽  
Vol 15 (7) ◽  
pp. 1101-1104 ◽  
Author(s):  
R.K. Gupta ◽  
O.P. Tiwari ◽  
A.K. Gupta ◽  
H.K. Das
Keyword(s):  
Endosperm Development ◽  
Wheat Endosperm ◽  
Synthesis And Degradation

scholarly journals Structural rearrangements of tubulin and actin during the cell cycle of the yeast Saccharomyces.

1984 ◽  
Vol 98 (3) ◽  
pp. 922-933 ◽  
Author(s):  
J V Kilmartin ◽  
A E Adams
Keyword(s):  
Cell Cycle ◽  
Mitotic Spindle ◽  
Neck Region ◽  
Wall Material ◽  
Double Labeling ◽  
Bud Emergence ◽  
Unusual Distribution ◽  
Significant Length ◽  
Cytoplasmic Microtubules ◽  
Mother Cells

The distribution of actin and tubulin during the cell cycle of the budding yeast Saccharomyces was mapped by immunofluorescence using fixed cells from which the walls had been removed by digestion. The intranuclear mitotic spindle was shown clearly by staining with a monoclonal antitubulin; the presence of extensive bundles of cytoplasmic microtubules is reported. In cells containing short spindles still entirely within the mother cells, one of the bundles of cytoplasmic microtubules nearly always extended to (or into) the bud. Two independent reagents (anti-yeast actin and fluorescent phalloidin) revealed an unusual distribution of actin: it was present as a set of cortical dots or patches and also as distinct fibers that were presumably bundles of actin filaments. Double labeling showed that at no stage in the cell cycle do the distributions of actin and tubulin coincide for any significant length, and, in particular, that the mitotic spindle did not stain detectably for actin. However, both microtubule and actin staining patterns change in a characteristic way during the cell cycle. In particular, the actin dots clustered in rings about the bases of very small buds and at the sites on unbudded cells at which bud emergence was apparently imminent. Later in the budding cycle, the actin dots were present largely in the buds and, in many strains, primarily at the tips of these buds. At about the time of cytokinesis the actin dots clustered in the neck region between the separating cells. These aspects of actin distribution suggest that it may have a role in the localized deposition of new cell wall material.

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