The Cytology of Xanthisma texanum D.C. IV. Megasporogenesis and Embryo Sac Formation, Pollen Mitosis and Embryo Formation

1956 ◽  
Vol 83 (6) ◽  
pp. 428 ◽  
Author(s):  
C. A. Berger ◽  
E. J. Feeley ◽  
E. R. Witkus
Keyword(s):  
Embryo Sac ◽  
Pollen Mitosis ◽  
Embryo Formation ◽  
Embryo Sac Formation

Embryology of Isotoma petraea

1970 ◽  
Vol 18 (2) ◽  
pp. 213 ◽  
Author(s):  
IC Beltran
Keyword(s):  
Mother Cell ◽  
Embryo Sac ◽  
Endosperm Development ◽  
Ovule Development ◽  
Polygonum Type ◽  
Development Patterns ◽  
Embryo Formation ◽  
Ring Bivalents ◽  
Form Ring ◽  
Embryo Sac Formation

Ovule development, embryo sac formation, and embryogeny of I. Petraea are described. The ovules are anatropous, unitegmic, and tenuinucellar. Meiosis in the megaspore mother cell is regular and the chromosomes with terminalized chiasmata form ring bivalents at metaphase 1. The Polygonum type embryo sac, Scutellaria type endosperm development, and Solanad embryo formation correspond with development patterns in other members of the Lobeliaceae.

scholarly journals The mac1 Gene: Controlling the Commitment to the Meiotic Pathway in Maize

Genetics ◽  
1996 ◽  
Vol 142 (3) ◽  
pp. 1009-1020 ◽  
Author(s):  
William F Sheridan ◽  
Nadezhda A Avalkina ◽  
Ivan I Shamrov ◽  
Tatyana B Batyea ◽  
Inna N Golubovskaya
Keyword(s):  
Female Gametophyte ◽  
Embryo Sac ◽  
Flowering Plants ◽  
Normal Female ◽  
Ovule Development ◽  
Partial Sterility ◽  
Embryo Sac Formation ◽  
Female Gametophyte Development ◽  
Normal Meiosis ◽  
Pleiotropic Mutation

Abstract The switch from the vegetative to the reproductive pathway of development in flowering plants requires the commitment of the subepidermal cells of the ovules and anthers to enter the meiotic pathway. These cells, the hypodermal cells, either directly or indirectly form the archesporial cells that, in turn, differentiate into the megasporocytes and microsporocytes. We have isolated a recessive pleiotropic mutation that we have termed multiple archesporial cells1 (macl) and located it to the short arm of chromosome 10. Its cytological phenotype suggests that this locus plays an important role in the switch of the hypodermal cells from the vegetative to the meiotic (sporogenous) pathway in maize ovules. During normal ovule development in maize, only a single hypodermal cell develops into an archesporial cell and this differentiates into the single megasporocyte. In macl mutant ovules several hypodermal cells develop into archesporial cells, and the resulting megasporocytes undergo a normal meiosis. More than one megaspore survives in the tetrad and more than one embryo sac is formed in each ovule. Ears on mutant plants show partial sterility resulting from abnormalities in megaspore differentiation and embryo sac formation. The sporophytic expression of this gene is therefore also important for normal female gametophyte development.

Apomixis and abnormal anther development in Calotis lappulacea Benth. (Compositae)

1968 ◽  
Vol 16 (1) ◽  
pp. 1 ◽  
Author(s):  
GL Davis
Keyword(s):  
New South ◽  
Embryo Sac ◽  
Pollen Grains ◽  
Anther Wall ◽  
Male Gametes ◽  
Globular Stage ◽  
South Wales ◽  
Vertical Division ◽  
Endosperm Formation ◽  
Embryo Sac Formation

A comparative study was made of material collected from four localities in New South Wales and Queensland and a number of embryological aberrations were found to be common to all districts. During microsporogenesis, certain tapetal cells not only failed to contribute to the tapetal periplasmodium but, after increasing in size, they separated from the anther wall and resembled one-, two-, or four-nucleate embryo sacs developing among the microspores. In one anther a structure was present which was very similar to a fully differentiated embryo sac. Although the pollen grains of some anthers contained male gametes, most anthers dehisced when the pollen was two-celled and some shrivelled soon after meiosis. Megasporogenesis was followed by the formation of linear tetrads of megaspores, but embryo sac formation was the result of somatic apospory and C. lappulacea appears to be an obligate apomict. The enlarging somatic cell usually invades the nucellar lobe and replaces the megaspores but one or more such celis commonly develop also in the chalaza, and up to eight embryo sacs were found in one ovule. Enlargement of a chalazal embryo sac sometimes resulted in penetration of the ovular epidermis and its invasion of the loculus as a haustorium-like structure. Extrusion of a developing embryo sac through the micropyle was common. Embryogeny is of the Asterad type, but vertical division of the terminal cell ca was delayed until after the basal cell cb had given rise to superposed cells m and ci. Polyembryony was common but only one embryo in each ovule reached maturity. Endosperm formation was independent of embryogeny but unless it was initiated before the globular stage of the embryo, the embryo sac collapsed and the embryo degenerated.

Tetrasporic Embryo-Sac Formation in Trisomic Sectors of Maize

Science ◽  
1964 ◽  
Vol 144 (3620) ◽  
pp. 874-876 ◽  
Author(s):  
M. G. Neuffer
Keyword(s):  
Embryo Sac ◽  
Embryo Sac Formation

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.

Analysis of Nondisjunction Induced by the R-X1 Deficiency during Microsporogenesis in Zea Mays L.

Genetics ◽  
1988 ◽  
Vol 119 (4) ◽  
pp. 975-980
Author(s):  
Z Y Zhao ◽  
D F Weber
Keyword(s):  
Zea Mays L ◽  
Embryo Sac ◽  
Mitotic Division ◽  
The Other ◽  
Chromosome 6 ◽  
Nucleolar Organizing Region ◽  
Sperm Nuclei ◽  
Embryo Sac Formation ◽  
And Control ◽  
Generative Nuclei

Abstract The r-X1 deficiency in maize induces nondisjunction at the second mitotic division during embryo sac formation. However, it was not known if this deficiency also induces nondisjunction during the microspore divisions. Microsporogenesis in plants lacking or containing this deficiency was compared using two approaches. First, chromosome numbers were determined in generative nuclei. Many (8.3%) of the generative nuclei in r-X1-containing plants were aneuploid; however, those from control plants were all haploid. Thus, this deficiency induces nondisjunction during the first microspore division. Second, nucleoli were analyzed in microspores. The only nucleolar organizing region in maize is on chromosome 6. If chromosome 6 underwent nondisjunction during the first microspore division, one nucleus in binucleate microspores would contain no nucleolus and the other would contain two nucleoli (or one nucleolus if the nucleoli fused). Only one (0.03%) microspore of this type was observed in control plants while 1.12% were found in r-X1-containing plants. Thus, the r-X1 deficiency induces nondisjunction of chromosome 6 during the first microspore division. However, both of the sperm nuclei in trinucleate microspores contained one nucleolus in r-X1-containing and control plants; thus, this deficiency does not induce nondisjunction of chromosome 6 (and presumably other chromosomes) during the second microspore division.

scholarly journals Apospory appears to accelerate onset of meiosis and sexual embryo sac formation in sorghum ovules

2011 ◽  
Vol 11 (1) ◽  
pp. 9 ◽  
Author(s):  
John G Carman ◽  
Michelle Jamison ◽  
Estella Elliott ◽  
Krishna K Dwivedi ◽  
Tamara N Naumova
Keyword(s):  
Embryo Sac ◽  
Embryo Sac Formation

DEVELOPMENT OF THE EMBRYO SAC AND EMBRYO OF TEFF, ERAGROSTIS TEF

1966 ◽  
Vol 44 (8) ◽  
pp. 1071-1075 ◽  
Author(s):  
Melak H. Mengesha ◽  
A. T. Guard
Keyword(s):  
Female Gametophyte ◽  
Leaf Blade ◽  
Floral Development ◽  
Flag Leaf ◽  
Embryo Sac ◽  
Eragrostis Tef ◽  
Careful Study ◽  
Embryo Formation ◽  
Self Pollination ◽  
Before And After

A careful study of the floral development of Eragrostis tef indicates that the flowers do not open and that self-pollination is the rule. Observations of the development of the female gametophyte show that it is of the normal monosporic type common to most angiosperms. The three antipodals divide several times as is common in grasses. Study of many ovules before and after fertilization showed absence of any apomictic type of embryo formation. Fertilization was found to occur in the basal floret of a spikelet when that floret was at the base of the flag leaf blade.

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