The time and duration of female meiosis in Lilium

1975 ◽  
Vol 188 (1093) ◽  
pp. 459-475 ◽  
Keyword(s):  
Mother Cell ◽  
Embryo Sac ◽  
Female Meiosis ◽  
Flower Bud ◽  
Pollen Mother Cells ◽  
Controlled Conditions ◽  
Mean Temperature ◽  
Mother Cells ◽  
Black Beauty

The time and duration of meiosis in ovules and anthers was estimated in plants of two Lilium hybrids (cultivars ‘Sonata’ and ‘Black Beauty’) grown under controlled conditions. Within each flower bud meiosis did not start in the embryo sac mother cell (e.m.c.) until about the time when meiosis in pollen mother cells (p.m.cs) was ended. In both cultivars meiosis lasted about 50% longer in e.m.cs than in p.m.cs. Thus, at a mean temperature of 20 ± 1 °C meiosis in ‘Sonata’ took 7.5 days in p.m.cs and 10.5 days in e.m.cs, while in ‘Black Beauty’ it took 10.5 days in p.m.cs and 16.0 days in e.m.cs.

scholarly journals Chiasma variation and control in pollen mother cells and embryo-sac mother cells of rye

1974 ◽  
Vol 23 (2) ◽  
pp. 185-190 ◽  
Author(s):  
E. D. G. Davies ◽  
G. H. Jones
Keyword(s):  
Embryo Sac ◽  
Genetic System ◽  
Chiasma Formation ◽  
Pollen Mother Cells ◽  
Controlling System ◽  
Mother Cells ◽  
And Control

SUMMARYMean chiasma frequencies and the amounts of between-bivalent chiasma variation were computed for pollen mother cells (p.m.c.) and embryo-sac mother cells (e.m.c.) of five distinct inbred rye lines. Despite the considerable differences for both these metrics shown by the different lines, very little variation was seen between p.m.c. and e.m.c. belonging to the same lines. It is concluded that chiasma formation in p.m.c. and e.m.c. of rye is governed and regulated by a single controlling system of genes and that variation in this genetic system is expressed identically in the two sexes.

scholarly journals Studies on the Morphology, Ontogeny and Embryology of the Flowers of Hedycarya Arborea J.R. et G. Forst. (Subfamily Monimioideae) and Laurelia Novae-Zelandiae A. Cunn. (Subfamily Atherospermoideae) of the Family Monimiaceae

2021 ◽  
Author(s):  
◽  
Frederick Bruce Sampson
Keyword(s):  
Generative Cell ◽  
Embryo Sac ◽  
Pollen Grains ◽  
Tetrad Stage ◽  
Pollen Mother Cells ◽  
The Family ◽  
Long Time ◽  
External Part ◽  
Mother Cells ◽  
And Function

<p>The inflorescences, flowers and the vascularization of floral parts of Hedycarya arborea and Laurelia novae-zelandiae were described and comparisons made with other members of the family in an attempt to determine the basic types of inflorescences, flowers and floral vascularization in the family. The vegetative, inflorescence and floral meristems of the two genera were compared. It was concluded that the vegetative apices of both had the tunica-corpus configuration typical of many other woody Ranales and other orders. The inflorescence apices were quite similar to the vegetative ones. The young floral apices are in a state of transition from a tunica-corpus to a mantle-core configuration and older floral apices had the mantle-core configuration, which is typical of the floral apices of many woody Ranales. Unusual features of the floral apices of Hedycarya and Laurelia were the lack of a pronounced rib meristem and the occurrence of relatively frequent divisions within vacuolate cells of the core. The ontogeny of the stamens of Hedycarya and Laurelia was described and comparisons were made. In both genera the micro-sporangium developed in a similar fashions: in Hedycarya 5-6 wall layers are formed inside the epidermis; in Laurelia there are 3-5 layers. Both genera had a typically thickened endothecium and a tapetum of the secretory type in which the tapetal cells become binucleate during the first meiotic division of the pollen mother cells. In Hedycarya the meiotic divisions of the pollen mother cells are of the successive type in which walls form by means of centrifugal cell plates Pollen grains remain in permanent tetrads in this genus. In Laurelia wall formation at the end of meiosis is of a modified simultaneous type, which may not have been hitherto described in the literature. Pollen grains are not in permanent tetrads. When the first division occurs in each microspore in Hedycarya, all four cells of a tetrad are at the same stage of division and the generative cell is cut off towards the distal face of the grain. Each microspore is in the two celled condition when shed. It was deduced that the generative cell is cut off against what represents a radial wall of the grain (with reference to the tetrad stage) in Laurelia. Pollen is shed in either the two or three celled condition. Comparisons were made with the development of microsporangia and male gametophytes in other woody Ranales. A study was made of the ontogeny, structure and function of the staminal appendages of Laurelia. It was found that the appendages function as nectaries, the nectar being predominantly sucrose. After a discussion of the various theories as to the morphological nature of the staminal appendages of the Laurales, it was concluded that they are morphologically staminodes. The carpels of Hedycarya and Laurelia have a basically similar ontogeny in which, as in the Lauraceae, the terminal stigmatic region develops from a solid terminal meristem in contrast to many woody Ranales in which the stigma-consists of crests which surround the external part of the cleft of the carpel. The ovules of Hedycarya and Laurelia resemble those of most other woody Ranales in being bitegmic, crassinucellate and anatropous with a monosporic 8-nucleate embryo sac of the Polygonum type. Both linear and T-shaped megaspore tetrads were found in the two genera. Laurelia has pseudocarps which develop after anthesis and enclose plumose achenes, but in Hedycarya the fruits are drupes. It was concluded that Laurelia and Hedycarya belong to two subfamilies which have been separated from each other for a long time and have undergone considerable evolution in different directions. It was also concluded that the Monimiaceae are closely related to the Lauraceae.</p>

The three-dimensional arrangement of chromosomes at meiotic metaphase I in normal and interchange heterozygotes of Briza humilis

1990 ◽  
Vol 97 (3) ◽  
pp. 565-570
Author(s):  
JANET M. MOSS ◽  
BRIAN G. MURRAY
Keyword(s):  
Mother Cell ◽  
Three Dimensional ◽  
Meiotic Metaphase ◽  
Central Position ◽  
Normal Plant ◽  
Serial Sections ◽  
Pollen Mother Cells ◽  
Sector Analysis ◽  
Mother Cells ◽  
Metaphase I

Pollen mother cells at metaphase I have been reconstructed from serial sections in normal and interchange heterozygotes of Briza humilis. The pollen mother cells have an irregular shape with a prominent projection from the tangential face into the anther loculus. The seven bivalents of the normal plant are usually arranged with one bivalent in a central position surrounded by a ring of the remaining six or as a ring of all seven bivalents. The central:peripheral distribution of quadrivalents is different in two different interchange plants; in a sector analysis, where cells are divided into four quarters relative to the tangential face of the pollen mother cell, the two plants also show differences in quadrivalent distribution, indicating that individual chromosomes occupy different positions in the cell. The relevance of these results to the positioning of quadrivalents in lateral squashes of meiotic metaphase I are discussed.

Meiotic crossing-over between sites on opposite sides of the centromeres of homoeologues is frequent in hybrid Aloeaceae

Genome ◽  
1990 ◽  
Vol 33 (2) ◽  
pp. 170-176 ◽  
Author(s):  
P. E. Brandham
Keyword(s):  
Pollen Mother Cell ◽  
Mother Cell ◽  
Crossing Over ◽  
Centromere Region ◽  
Short Chromosome ◽  
Pollen Mother Cells ◽  
Mother Cells ◽  
Homoeologous Chromosomes

During meiosis, long and short arms of acrocentric homoeologues pair and cross over in the centromere region in 95 (66.9%) of 142 hybrids of differing parentage in the monocotyledon family Aloeaceae. A characteristic configuration, the L–S bridge, is produced at anaphase I with frequencies ranging from <1 to 48% of pollen mother cells and in up to three bivalents per pollen mother cell. Too frequent to be due to inversion hybridity, L–S crossing-over most probably results from straight, noninverted pairing between nonhomologous proximal segments of the long and short chromosome arms following centromere mismatching in the heteromorphic bivalents. It is suggested that there are several lengths of DNA in different regions of homoeologous chromosomes, but perhaps concentrated around the centromere, that are sufficiently similar to recognize each other, pair, and cross over when brought together in a heteromorphic bivalent with mismatching of centromeres.Key words: Aloeaceae, hybrid, meiosis, nonhomologous pairing, crossing-over.

Studies on the Monimiaceae. III. Gametophyte development of Laurelia novae-zelandiae A. Cunn. (subfamily Atherospermoideae)

1969 ◽  
Vol 17 (3) ◽  
pp. 425 ◽  
Author(s):  
FB Sampson
Keyword(s):  
Generative Cell ◽  
Embryo Sac ◽  
Radial Wall ◽  
Tetrad Stage ◽  
Polygonum Type ◽  
Gametophyte Development ◽  
Pollen Mother Cells ◽  
Secretory Type ◽  
Mother Cells ◽  
Unusual Type

Floral ontogeny and gametophyte development of the New Zealand endemic species Laurelia novae-zelandiae is described. The microsporangium has three to five wall layers inside the epidermis, including a typically thickened endothecium and a tapetum of the secretory type in which the cells become binucleate during the first meiotic division of pollen mother cells. Cytokinesis of pollen mother cells is of an unusual type in which centrifugal cell plates do not develop until the end of meiosis 11. The generative cell of the pollen grain is cut off against what represents a radial wall of the grain with reference to the tetrad stage. Pollen is two- or three-celled when shed. Ovules are bitegmic, crassinucellate, and anatropous with a Polygonum type of embryo sac development.

The time and duration of female meiosis in wheat, rye and barley

1973 ◽  
Vol 183 (1072) ◽  
pp. 301-319 ◽  
Keyword(s):  
Hordeum Vulgare ◽  
Nuclear Dna ◽  
Higher Plants ◽  
Embryo Sac ◽  
Nuclear Dna Content ◽  
Male Meiosis ◽  
Female Development ◽  
Female Meiosis ◽  
Male And Female ◽  
Mother Cells

Few recent investigations have been made of female meiosis in cereals, and almost nothing is known about the duration of female meiosis in higher plants. Consequently, the time and duration of female meiosis in Triticum aestivum , Hordeum vulgare and Secale cereale have been studied. The appearance of the embryo sac mother cell (e. m. c.) and of the meiotic nuclei during female meiosis in Hordeum vulgare is described and illustrated. In the species studied, each floret contains only one ovary with a single e. m. c., and meiosis is almost synchronous in the pollen mother cells from all three anthers. Conse­quently, it is possible to make precise comparisons between the stages of male and female development within individual florets. Data from these comparisons, together with know­ledge previously determined of the duration of male meiosis in these species, allowed the estimation of the time and duration of female meiosis fairly accurately for T. aestivum and H. vulgare and approximately for S. cereale . The results showed that for H. vulgar and T. aestivum grown at 20°C, the duration of female meiosis was very similar to the duration of male meiosis. Furthermore, on average male and female meiosis occurred almost synchronously. In S. cereale however, male meiosis preceeded female meiosis by about 15 h. Growing T. aestivum under environmental stress induced asynchrony between male and female development at meiosis. Synchrony was not re-established after a long period under normal conditions. Nuclear DNA content and ploidy level are known to be important factors determining or affecting the duration of male meiosis. These factors appear to play an important role in controlling the duration of female meiosis also.

scholarly journals The dyad gene is required for progression through female meiosis in Arabidopsis

Development ◽  
2000 ◽  
Vol 127 (1) ◽  
pp. 197-207 ◽  
Author(s):  
I. Siddiqi ◽  
G. Ganesh ◽  
U. Grossniklaus ◽  
V. Subbiah
Keyword(s):  
Mother Cell ◽  
Megaspore Mother Cell ◽  
Female Gametophyte ◽  
Molecular Mechanisms ◽  
Higher Plants ◽  
Embryo Sac ◽  
Initial Step ◽  
Female Meiosis ◽  
Female Germ Cell ◽  
Further Development

In higher plants the gametophyte consists of a gamete in association with a small number of haploid cells, specialized for sexual reproduction. The female gametophyte or embryo sac, is contained within the ovule and develops from a single cell, the megaspore which is formed by meiosis of the megaspore mother cell. The dyad mutant of Arabidopsis, described herein, represents a novel class among female sterile mutants in plants. dyad ovules contain two large cells in place of an embryo sac. The two cells represent the products of a single division of the megaspore mother cell followed by an arrest in further development of the megaspore. We addressed the question of whether the division of the megaspore mother cell in the mutant was meiotic or mitotic by examining the expression of two markers that are normally expressed in the megaspore mother cell during meiosis. Our observations indicate that in dyad, the megaspore mother cell enters but fails to complete meiosis, arresting at the end of meiosis 1 in the majority of ovules. This was corroborated by a direct observation of chromosome segregation during division of the megaspore mother cell, showing that the division is a reductional and not an equational one. In a minority of dyad ovules, the megaspore mother cell does not divide. Pollen development and male fertility in the mutant is normal, as is the rest of the ovule that surrounds the female gametophyte. The embryo sac is also shown to have an influence on the nucellus in wild type. The dyad mutation therefore specifically affects a function that is required in the female germ cell precursor for meiosis. The identification and analysis of mutants specifically affecting female meiosis is an initial step in understanding the molecular mechanisms underlying early events in the pathway of female reproductive development.

The time and duration of preleptotene chromosome condensation stage in Lilium hybrid cv. Black Beauty

1975 ◽  
Vol 188 (1093) ◽  
pp. 477-493 ◽  
Keyword(s):  
Maximum Degree ◽  
Meiotic Chromosome ◽  
Embryo Sac ◽  
Lilium Longiflorum ◽  
Chromosome Condensation ◽  
Late Prophase ◽  
Significant Function ◽  
Mother Cells ◽  
Black Beauty ◽  
Pairing Behaviour

A period of chromosome condensation followed by decondensation occurs between premeiotic interphase and leptotene in Lilium hybrid cv. ‘Black Beauty’. The duration of this period was estimated to be about 1.16 days in pollen mother cells (p. m. cs) of plants grown at 20 °C. Preleptotene chromosome condensation and contraction also occurred in embryo sac mother cells (e. m. cs) of ‘Black Beauty’. However, the maximum degree of chromosome contraction at the preleptotene condensation stage was much greater in p. m. cs than in e. m. cs. Moreover, the preleptotene condensation and decondensation stage was apparently shorter in e. m. cs (about 0.7 days) than in p. m. cs. The developmental behaviour of p. m. c. chromosomes during pre­leptotene condensation and decondensation was essentially the same as that described by Walters (1970, 1972) for the corresponding stages in Lilium longiflorum cv. ‘Croft’. A brief illustrated description is given of the appearance of p. m. cs at various stages of preleptotene chromosome condensation in both methylene blue stained anther sections, and in Feulgen stained anther squashes. ‘Black Beauty’ p. m. cs entered preleptotene chromosome condensation stage from G2 of premeiotic interphase having completed DNA synthesis. All the p. m. cs within an anther loculus underwent preleptotene chromo­some condensation stage with a degree of synchrony not less than that found at early first meiotic prophase. At maximum chromosome contration the diploid chromosome number (2 n = 24) could often be counted, but no evidence of association of chromosomes was seen. At this stage the appearance of the chromosomes was indistinguishable from that of late prophase or prometaphase chromosomes at mitosis. Thereafter chromo­somes underwent decondensation and elongation and eventually passed into leptotene without first entering any other stage. The nature and possible significance of preleptotene chromosome condensation and decondensation are discussed. The appearance and behaviour of chromosomes at preleptotene condensation stage is the same as that displayed by chromosomes at mitotic prophase. Similarly, the appearance and behaviour of chromosomes at preleptotene decondensation is indistinguishable from that normally seen at mitotic telophase. It is suggested, therefore, that preleptotene condensation and decondensation represent a true mitotic reversion in which metaphase and anaphase are omitted. In normal Lilium genotypes meiosis is initiated by p. m. cs at G2 of premeiotic interphase. In ‘Black Beauty’, however, the control regu­lating the initiation of meiosis apparently is effective later in the cell cycle and acts only after p. m. cs have entered mitotic prophase. It is concluded that preleptotene chromosome condensation stage has no effect on normal meiotic chromosome pairing behaviour and probably has no significant function. Two parallel threads (chromatids) are visible in chromosomes at preleptotene condensation stage while, in chromo­somes at leptotene, invariably only a single thread is seen. It is suggested, therefore, that chromosomes at maximum preleptotene condensation can­not enter a meiotic sequence without first undergoing a within-chromosomal reorganization of their chromatin, and that preleptotene chromo­some decondensation stage represents such a reorganization.

scholarly journals Megaspore development in Oenothera rubricalyx, with a note on chromosome linkage in Oenothera angustissima

1929 ◽  
Vol 105 (739) ◽  
pp. 499-517 ◽  
Keyword(s):  
Embryo Sac ◽  
Reduction Division ◽  
Single Plant ◽  
Female Side ◽  
Male And Female ◽  
Homologous Chromosomes ◽  
Pollen Mother Cells ◽  
Reciprocal Hybrids ◽  
Single Cross ◽  
Mother Cells

It has long keen known (Gates, 1908) that at meiosis, in the pollen mother-cells of Oenothera, the chromosomes do not of necessity become paired, but may remain joined together in chains. Of recent years it has transpired that the amount of pairing and chromosome linkage is constant within each species and each mutant. Morphologically different hybrids resulting from a single cross may differ in the amount of linkage exhibited, but within each hybrid type the linkage is constant. Reciprocal hybrids may differ from one another morphologically and cytologically, but each form may breed true if a sufficient number of chromosomes are linked; for, once determined, the amount of linkage in any form is unvarying. In certain other genera of plants various linkages of chromosomes have been found, but Oenothera is at present unique in the degree and constancy of linkage observed. The view has therefore been expressed (Gates, 1928) that the small-dowered species, nearly all of which show complete chromosome linkage, breed true on account of this linkage and are really permanent hybrids, the formation of a ring of 14 chromosomes resulting from the bringing together of non-homologous chromosomes in the fertilization nucleus. Before any very definite conclusions could be drawn from these results it was necessary to find out whether the linkage, which is evident in the nucleus of the pollen mother-cells, also prevails in the nucleus of the embryo-sac mother-cell at reduction division. From an early paper of Davis on Oe. biennis (1911) it was obvious that some suck linkage does occur on the female side. The present work was undertaken primarily to determine whether similar linkages occur in the two types of mother-cells of a single plant. Before the work was completed Håkansson (1928) showed that the process of reduction is similar on the male and female side in Oe. Lamarckiana and several of its derivatives.

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