Embryo sac development in soybean: ultrastructure of megasporogenesis and early megagametogenesis

1989 ◽  
Vol 67 (10) ◽  
pp. 2841-2849 ◽  
Author(s):  
M. W. Folsom ◽  
D. D. Cass
Keyword(s):  
Uniform Distribution ◽  
Water Flux ◽  
Embryo Sac ◽  
Longitudinal Axis ◽  
Large Vacuole ◽  
Putative Protein ◽  
Golgi Vesicles ◽  
Chalazal Megaspore ◽  
Axis Parallel ◽  
Cell Layers

The soybean ovule is bitegmic with the megasporocyte three to four cell layers beneath the nucellar epidermis. The megasporocyte is much larger than the surrounding nucellar cells, is connected to the nucellus by plasmodesmata, and at this stage exhibits a cytoplasmic density comparable with cells of the nucellus. After meiosis, the chalazal megaspore becomes functional in megagametogenesis. It alone retains plasmodesmatal connections to the nucellus. Chalazal megaspore expansion is accompanied by development of many small vacuoles having a uniform distribution. The first megaspore mitosis results in two nuclei lying on an axis parallel to the longitudinal axis of the embryo sac. Ultimately, these two nuclei are separated by a large vacuole. Numerous Golgi vesicles and proteinlike bodies are observed along the periphery of vacuoles in the 1-, 2-, and 4-nucleate embryo sacs. As the contents of vesicles and proteinlike bodies are observed deposited in vacuoles, it is probable that they both add osmotica to the vacuoles, thus promoting a water flux. We believe that the production of Golgi vesicles and putative protein bodies may be important in the formation and expansion of the large vacuole that appears to drive embryo sac expansion during early megagametogenesis in soybean. It is also believed that the timing to this vacuole's development has important developmental consequences.

Embryological studies in the compositae, I. Sporogenesis, Gametogenesis, and Embryogeny in Cotula australis (Less.) Hook. F

1962 ◽  
Vol 10 (1) ◽  
pp. 1 ◽  
Author(s):  
GL Davis
Keyword(s):  
Mother Cell ◽  
Megaspore Mother Cell ◽  
Embryo Sac ◽  
Subsequent Development ◽  
Pollen Grains ◽  
Archesporial Cell ◽  
Polygonum Type ◽  
Wall Formation ◽  
Chalazal Megaspore

Cotula australis has a discoid heterogamous capitulum in which the outermost three whorls of florets are female and naked. The bisexual disk florets are fully fertile and have a four-lobed corolla with four shortly epipetalous stamens. The anthers contain only two microsporangia. Wall formation and microsporogenesis are described and the pollen grains are shed at the three-celled condition. The ovule is teguinucellate and the hypodermal archesporial cell develops directly as the megaspore mother cell. Megasporogenesis is normal and the monosporio embryo sac develops from the chalazal megaspore. Breakdown of the nucellar epidermis takes place when the embryo sac is binucleate and its subsequent development follows the Polygonum type. The synergids extend deeply into the micropyle and one persists until late in embryogeny as a haustorium. The development of the embryo is of the Asterad type, and the endosperm is cellular. C. coronopifolia agrees with C. australis in the presence of only two microsporangia in each anther and the development of a synergid haustorium.

Evaluation of skin displacement in the equine neck

2014 ◽  
Vol 10 (3) ◽  
pp. 181-186 ◽  
Author(s):  
A. Bergh ◽  
A. Egenvall ◽  
E. Olsson ◽  
M. Uhlhorn ◽  
M. Rhodin
Keyword(s):  
Mixed Models ◽  
Sagittal Plane ◽  
Cervical Vertebrae ◽  
Statistical Significance ◽  
Longitudinal Axis ◽  
Joint Motion ◽  
Skin Marker ◽  
Significant Difference ◽  
Axis Parallel ◽  
Kinematic Studies

Kinematic studies, using reflective skin markers, are commonly used to investigate equine joint motion in equitation science and for rehabilitation purposes. In order to interpret the registrations accurately, the degree of skin displacement has been described for the limbs and back, but not yet for the neck. The aim of the present study was to measure sagittal plane skin displacement in the equine neck. Radiopaque skin markers were applied to the skin over the first six cervical vertebrae of six healthy horses. Latero-lateral radiographs were taken in three standardised neck positions in the sagittal plane: control (horizontal neck), ‘on the bit’ and ‘nose to carpus’. The scales of the images were normalised and calculation of skin displacement was done by use of a coordinate system, dividing the displacement along an x-axis parallel to the vertebra's longitudinal axis and a y-axis perpendicular to the x-axis. Mixed models analysis was employed to study the differences in distances in x- and y-directions, and statistical significance was set to PÃ0.05. Between control and ‘nose to carpus’ positions, there were significant differences in skin marker locations, relative to the underlying vertebrae, in the x-direction for C1-6, and in y-direction for C3-6. Between normal and ‘on the bit’ positions, there were significant difference in both x- and y-directions for C6. Differences in marker locations along x- and y-axes, respectively, were 3±9 mm and 44±14 mm. The outcome of this study indicates that skin displacement should be considered when investigating equine neck motion with skin marker methodology.

scholarly journals Megaspore competition in F1 and F2 hybrids between Oenothera hookeri and Oe. suaveolens

2014 ◽  
Vol 53 (3) ◽  
pp. 317-324 ◽  
Author(s):  
Renata Śnieżko
Keyword(s):  
Embryo Sac ◽  
Hybrid Plant ◽  
Plant Genome ◽  
Haploid Genome ◽  
Oenothera Hookeri ◽  
Chalazal Megaspore ◽  
F2 Hybrids ◽  
Embryo Sac Formation ◽  
Short Time

Megasporogenesis and development of the embryo sac were investigated in F<sub>1</sub> and F<sub>2</sub> hybrids from crosses of <em>Oe. hookeri</em> and <em>Oe. suaveolens</em>. All hybrids form heteropolar and homopolar magaspore tetrads; the embryo sac, however, usually develops from the micropylar megaspore. Its development may occur immediately after degeneration of three other megaspores or after a period of competition between both apical megaspores. They develop simultaneously for a relatively short time, after which the growth of the chalazal megaspore is inhibited, although the latter does not degenerate. The micropylar megaspore as a rule develops without disturbances into the embryo sac, but in some ovules it is formed from the chalazal megaspore or double ones arise from both apical megaspores of the tetrad. The frequency of the micropylar embryo sac formation seems to be dependent above all on the hybrid plant genome and not on the haploid genome of the megaspore.

Sporogenesis, Gametogenesis, and embryogeny of Wahlenbergia bicolor N. Lothian

1963 ◽  
Vol 11 (2) ◽  
pp. 152 ◽  
Author(s):  
G Want
Keyword(s):  
Mother Cell ◽  
Embryo Sac ◽  
Pollen Grains ◽  
Type A ◽  
Middle Layer ◽  
Anther Wall ◽  
Suspected Case ◽  
Polygonum Type ◽  
Chalazal Megaspore ◽  
Coastal Species

In Wahlenbergia bicolor, the anther wall is composed of four layers: epidermis, endothecium, middle layer, and tapetum. Wall formation and microsporogenesis are described, and the pollen grains are shed at the two-celled condition. The ovules are tenuinucellate, with a hypodermal archesporial cell which develops directly as the megaspore mother cell. Megasporogenesis is normal, and a monosporic eight-nucleate embryo sac of the most common Polygonum type develops from the chalazal megaspore. The antipodals degenerate before fertilization. The development of the embryo is of the solanad type. A suspected case of polyembryony was observed. The endosperm is cellular from its inception, and so conforms to the Codonopsis type. A micropylar and a chalazal haustoriurn, both consisting of two uninucleate cells, are formed from the endosperm. Comparative studies were made with a known but as yet undescribed coastal species of Wahlenbergia, and no differences were found.

Identification of the Mechanical Characteristics of 3D Printed NinjaFlex®

2019 ◽  
Author(s):  
Patrick Messimer ◽  
Brendan O’Toole ◽  
Mohamed Trabia
Keyword(s):  
Tensile Properties ◽  
Mechanical Characteristics ◽  
Thermoplastic Polyurethane ◽  
Longitudinal Axis ◽  
Fused Deposition Modelling ◽  
Wearable Electronics ◽  
Limited Information ◽  
Fused Deposition ◽  
Axis Parallel ◽  
3D Printers

Abstract NinjaFlex is a flexible thermoplastic polyurethane (TPU) material manufactured for use with Fused Deposition Modelling 3D printers. It is widely available, relatively inexpensive, and is useful in various applications including gaskets, wearable electronics, and customized prosthetics because of its great flexibility and strength. The objective of this research was to expand on the limited information available regarding the mechanical characteristics of NinjaFlex and learn how infill density and printing orientation influence those characteristics. An experiment was designed using the ASTM D638-14 standard to evaluate tensile properties of NinjaFlex specimens printed in two different orientations with their longitudinal axis parallel to the printing surface and with their longitudinal axis normal to the printing surface. Four different infill densities were used. Specimens were subjected to tensile loading along their longitudinal axes. A calibrated load cell measured applied force while a camera filmed the experiment for determining the corresponding extension using computer vision methods. The results show that NinjaFlex has sizably greater ultimate strength, elongation, and toughness when loaded parallel to its print layers then when loaded normal to its print layers. The effects of infill density on tensile properties vary depending on loading direction relative to the print layer direction.

scholarly journals Anatomy Differs for Aborting and Nonaborting Pistillate Flowers in Pecan

1994 ◽  
Vol 119 (5) ◽  
pp. 949-955 ◽  
Author(s):  
I.E. Yates ◽  
Darrell Sparks
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Embryo Sac ◽  
Central Nucleus ◽  
Tissue Necrosis ◽  
Carya Illinoensis ◽  
Anatomical Features ◽  
Cell Layers ◽  
Scanning Electron

Comparative anatomical features of nonaborting (normal) and aborting pistillate flowers were examined with light and scanning electron microscopy during the first of four physiological drops characteristic of pecan [Carya illinoensis (Wangenh.) C. Koch]. Flowers sampled over a 3-year period from a protandrous and a protogynous cultivar (Desirable and Wichita, respectively) did not have any tissue necrosis. Diameter, length, and weight of aborting intact flowers were significantly less at 65%, 55%, and 30%, respectively, in aborting than nonaborting intact flowers. A common anatomical deviation in aborting flowers was that the integument was less extended over the nucellus of the ovule than in nonaborting flowers. The number of parenchymal nucellus cell layers lateral to the embryo sac often was less in aborting than nonaborting flowers. Embryo sacs were inflated in nonaborting flowers, but appeared deflated in aborting flowers. Both sacs had a conspicuous central nucleus, egg, and synergid, with a second synergid evident in the embryo sacs of some nonaborting flowers. Thus, aborting pecan flowers had incompletely developed ovules with no evidence of necrosis.

Embryo sac development in some South African Lantana species (Verbenaceae)

Bothalia ◽  
1984 ◽  
Vol 15 (1/2) ◽  
pp. 161-166 ◽  
Author(s):  
J. J. Spies
Keyword(s):  
South African ◽  
Embryo Sac ◽  
Lantana Camara ◽  
The South ◽  
Polygonum Type ◽  
Embryo Sac Development ◽  
Chalazal Megaspore

Evidence that the South African Lantana camara L. complex only produces sexual embryo sacs is provided. It is shown that the archesporium occasionally divides mitotically and that both archesporia form tetrads. The chalazal megaspore of one tetrad and the micropylar megaspore of the second tetrad develop into Polygonum type embryo sacs. L. rugosa Thunb. also forms Polygonum type embryo sacs. The L. rugosa embryo sac has a much more densely packed cytoplasm, smaller vacuole and the position of the polar nuclei differs from that of the L. camara embryo sac. It is possible to distinguish between  L. camara and  L. rugosa on their embryo sac morphology alone.

Embryology of Macroptilium arenarium (Leguminosae)

2006 ◽  
Vol 54 (6) ◽  
pp. 531 ◽  
Author(s):  
M. Gotelli ◽  
B. Galati ◽  
P. Hoc
Keyword(s):  
Comparative Study ◽  
Sexual Reproduction ◽  
Embryo Sac ◽  
Pollen Grains ◽  
Linear Arrangement ◽  
Polygonum Type ◽  
Chalazal Megaspore ◽  
Chasmogamous Flowers

Macroptilium arenarium (Bacigalupo) S.I.Drewes & R.A.Palacios produces two floral morphs, aerial chasmogamous flowers and cleistogamous flowers in geophyte racemes. A comparative study of the sporogenesis, gametogenesis and the development of the related sporophytic structures in both floral morphs is reported. The anther is tetrasporangiate, its wall consists of epidermis, endothecium, one or two middle layers and an uninucleate secretory tapetum. The mature endothecium presents fibrilar thickenings that are more developed in cleistogamous flowers. Pollen grains are tricolporate, angulaperturate, and are shed at bicellular stage. The ovule is crassinucelate, bitegmic and anacampylotropous. Megaspore tetrads with linear arrangement have been observed in chasmogamous flowers, whereas only megaspore dyads have been found in cleistogamous flowers. In both floral morphs the chalazal megaspore develops into an embryo sac of Polygonum type. Apomixis is considered as a possible replacement for sexual reproduction in cleistogamous flowers.

scholarly journals Desarrollo del gametofito femenino de Tagetes patula (Asteraceae)

2017 ◽  
pp. 5
Author(s):  
Marcelina García-Aguilar ◽  
E. Mark Engleman ◽  
Eulogio Pimienta-Barrios
Keyword(s):  
Seed Development ◽  
Early Development ◽  
Mother Cell ◽  
Megaspore Mother Cell ◽  
Embryo Sac ◽  
Tagetes Patula ◽  
Polygonum Type ◽  
Chalazal Megaspore ◽  
The Family ◽  
Apomictic Reproduction

The genus Tagetes reproduces sexually by seed, but recent morphological and hybridization studies in Tagetes patula suggest an apomictic type of reproduction (seed development without fertilization). In order to determine the sexual or apomictic origen of the embryo, we have studied megasporogenesis, megagametogenesis and the early development of the embryo. Tagetes patula L. has a typical ovule for the family Asteraceae: anatropous, unitegmic, tenuinucellate and with basal placentation. A single hypodermal archesporial cell develops directly as the megaspore mother cell. Megaspogenesis is normal and embryo sac develops from the chalazal megaspore. The embryo sac is of the Polygonum type. Female ray flowers show irregularities in megagametophyte development such as formation of more than eight nuclei, inverted polarity and incomplete differentiation of the megagametophyte cells in mature flowers. These irregularities do not necessarily prove apomictic reproduction in Tagetes patula.

ERROR ESTIMATE OF ACCELEROMETER MEASURING ACCELERATION OF THE CAR ON THE ROAD WITH LONGITUDINAL SLOPE

2015 ◽  
Vol 2 (2) ◽  
pp. 515-521
Author(s):  
Тесля ◽  
V. Teslya ◽  
Абрамов ◽  
D. Abramov
Keyword(s):  
Measurement Error ◽  
Error Estimate ◽  
Longitudinal Axis ◽  
The Road ◽  
Axis Parallel ◽  
Longitudinal Slope ◽  
On The Road ◽  
Sensitive Axis

The estimation of the magnitude of the error of accelerometer along sensitive axis, parallel to the longitudinal axis of the vehicle, with its accelerated movement on the road with longitudinal slope is done. An amendment to the testimony of the accelerometer, which allows reducing measurement error to acceptable values introduced

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