Relationships among taxa of Elymus (Poaceae: Triticeae) in Australia: reproductive biology

2003 ◽  
Vol 16 (5) ◽  
pp. 633 ◽  
Author(s):  
Michelle A. Murphy
Keyword(s):  
Chromosome Numbers ◽  
Mother Cell ◽  
Megaspore Mother Cell ◽  
Species Complex ◽  
Seed Set ◽  
Embryo Sac ◽  
Mature Embryo ◽  
The Other ◽  
Polymorphic Forms ◽  
Tribe Triticeae

Nomenclatural and taxonomic problems are common among members of the tribe Triticeae and in particular the genus Elymus L. For the Australian representatives of this genus, confusion surrounds the number of taxa present, and which literature belongs to which 'taxon'. The literature indicates at least four major taxa: (1) long-awned forms of E. scaber var. scaber equated to E. rectisetus, (2) shorter-awned forms of E. scaber var. scaber, (3) the very short-awned E. multiflorus and (4) E. scaber var. plurinervis. In addition, a form intermediate between the long- and short-awned forms of E. scaber, as well as populations containing polymorphic forms have been reported. A recent taxonomic treatment of the species complex identified a fifth taxon, E. sp. A. This taxon has previously been identified as E. scaber or E. multiflorus. The current study examined 500 pistils from megaspore mother cell to mature embryo sac, somatic and haploid chromosome numbers, and seed set of nine populations of E. scaber var. scaber sensu lato (common wheatgrass). They included forms equating to E. rectisetus, E. scaber and E. sp. A, a population with intermediate characteristics, and three polymorphic populations. Taxon (1) above is apomictic; taxon (2) contains two entities, one a facultative apomict encompassing the intermediate and polymorphic populations, and the other, the sexual E. sp. A. Exclusive sexuality was also confirmed for material of (3) and (4).

Megasporogenesis and megagametogenesis in Pelargonium × hortorum

1973 ◽  
Vol 51 (3) ◽  
pp. 607-612 ◽  
Author(s):  
Annie H. Tsai ◽  
Patricia M. Harney ◽  
R. L. Peterson
Keyword(s):  
Mother Cell ◽  
Megaspore Mother Cell ◽  
Outer Integument ◽  
Embryo Sac ◽  
Mature Embryo ◽  
Polar Nucleus ◽  
Archesporial Cell ◽  
Linear Tetrad ◽  
Polygonum Type ◽  
Cell Functions

The ovary of Pelargonium × hortorum contains five pairs of superposed ovules in five locules. These ovules are bitegmic and crassinucellar and the upper ovule of each pair is campylotropous while the lower one is anatropous. A single archesporial cell functions directly as the megaspore mother cell. Meiotic division of the megaspore mother cell results in the formation of a linear tetrad of megaspores of which the chalazal megaspore is functional. Embryo sac development is of the polygonum type. Rapid degeneration of the three antipodals occurs followed by the fusion of the two polar nuclei. Therefore, the mature embryo sac contains the egg, the two synergids, and the fused polar nucleus. Double fertilization takes place. Ninety-two percent of the fertilized ovules of P. × hortorum cv. ‘Purple Heart’ are found in the upper position.The two integuments are initiated before the differentiation of the archesporial cell. Cells of the outer layer of the outer integument and the inner layer of the inner integument deposit tannins. The nucellus develops through divisions of the parietal cells of the nucellar epidermal cells.

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.

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.

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.

Ultrastructural observations of the mature megagametophyte and the fertilization in wheat (Triticum aestivum)

1985 ◽  
Vol 63 (2) ◽  
pp. 163-178 ◽  
Author(s):  
Ruilin You ◽  
William A. Jensen
Keyword(s):  
Triticum Aestivum ◽  
Pollen Tube ◽  
Cell Walls ◽  
Embryo Sac ◽  
Mature Embryo ◽  
Central Cell ◽  
The Other ◽  
Egg Cell ◽  
Filiform Apparatus ◽  
Egg Apparatus

The mature embryo sac of wheat contains an egg apparatus composed of an egg cell and two synergids at the micropylar end, a central cell with two large polar nuclei in the middle, and a mass of 20 to 30 antipodals at the chalazal end. A comparison was made of the ultrastructural features of the various cells of the embryo sac. The features included the position of the nucleus and vacuoles, the number, structure, and distribution of organelles, and the extent of the cell walls surrounding each cell. The pollen tube enters one synergid through the filiform apparatus from the micropyle. The penetration and discharge of the pollen tube causes the further degeneration of that synergid, which had already undergone changes before pollination. The second synergid does not change further in appearance following the penetration of the first by the pollen-altered tube. Half an hour after pollination at 20–25 °C, two male nuclei are seen in the cytoplasm of the egg and the central cell. At about 1 h after pollination, one sperm has made contact with the egg nucleus, while the other sperm is fusing with one of the polar nuclei.

Embryological background of low seed set in distylous common buckwheat (Fagopyrum esculentum Moench) with biased morph ratios, and biostimulant-induced improvement of it

2017 ◽  
Vol 68 (7) ◽  
pp. 680 ◽  
Author(s):  
Aneta Słomka ◽  
Klaudia Michno ◽  
Franciszek Dubert ◽  
Michał Dziurka ◽  
Przemysław Kopeć ◽  
...  
Keyword(s):  
Gibberellic Acid ◽  
Seed Set ◽  
Embryo Sac ◽  
Mature Embryo ◽  
Fagopyrum Esculentum ◽  
Naphthaleneacetic Acid ◽  
Common Buckwheat ◽  
Morph Ratios ◽  
Fagopyrum Esculentum Moench ◽  
Compatible Pollen

The biased ratio (1 : 2.7–1 : 19) of long-styled Pin and short-styled Thrum flowers (anisoplethy) in common buckwheat (Fagopyrum esculentum) with low seed set (9.8–33.1%) is documented for the first time in two cultivars (Kora, Panda) and two strains (PA13, PA14). To establish the reasons for low grain yield we studied pollen, embryo sacs, embryos, counted stigmas with compatible pollen and with compatible pollen tubes, and recorded seed set under semi-controlled conditions with open access of pollinators. We also sought to improve seed yield via exogenous application of eight biostimulants at the beginning of flowering. Pin pollen supply to Thrum stigmas was low, due to the imbalance of flower morphs. This did not affect seed set or male success in either flower morph. The pollen of Pin or Thrum was highly viable (97.9–99.9%) in all studied cultivars and strains, germinating well on compatible stigmas. The female success of both flower types was much lower; 49–59% of the ovules exhibited signs of degeneration (whole flower buds, ovules only) or abortion (mature embryo sacs, proembryos, embryos); the highest share of mature embryo sac abortions resulted from degeneration of synergids or the whole egg apparatus. Three biostimulants (Gibberellic acid, putrescine, Asahi SL) in PA13 and six (1-Naphthaleneacetic acid, Gibberellic acid, TYTANIT, putrescine, 6-Benzylaminopurine, Asahi SL) in PA14 decreased embryo abortions (4–12 fold) and increased seed set (0.4–2.4 times), but seed set was still low and never exceeded 33% (the highest value of the untreated with biostimulants plants). Biostimulant treatments were most effective on PA14 strain increasing seed set in 7 out of 8 treatments. These were Gibberellic acid, putrescine and Asahi SL improving seed set of two among four analysed genotypes.

Embryological studies in the compositae. II. Sporogenesis, Gametogenesis, and Embryogeny in Ammobium alatum R. Br.

1962 ◽  
Vol 10 (2) ◽  
pp. 65 ◽  
Author(s):  
GL Davis
Keyword(s):  
Mother Cell ◽  
Megaspore Mother Cell ◽  
Considerable Increase ◽  
Embryo Sac ◽  
Archesporial Cell ◽  
Cell Generation ◽  
Perennial Herb ◽  
Wall Formation ◽  
Sequence Of Events

Ammobium alatum is a perennial herb whose discoid-homogarnous capitula are surrounded by several rows of involucral bracts with white radiating laminae. Four microsporangia are present in each anther and their development and dehiscence are described. The ovule is anatropous, unitegmic, and tenuinucellate. The archesporial cell is hypodermal in origin and, following considerable increase in size, it functions directly as the megaspore mother cell. Cytokinesis and wall formation are postponed until after Meiosis 11 and a dyad is formed in which each cell is binucleate. The embryo sac is bisporic and its development is a variation of the Allium type. After fertilization, the surviving synergid may increase greatly in size but it does not extend into the micropyle and it collapses when the embryo reaches the seventh cell generation. Embryogeny is of the Asterad type and the sequence of events leading up to maturation of the embryo and of the fruit is described.

Reproductive development in two species of Darwinia Rudge (Myrtaceae)

1969 ◽  
Vol 17 (2) ◽  
pp. 215 ◽  
Author(s):  
N Prakash
Keyword(s):  
Embryo Sac ◽  
Pollen Grains ◽  
Reproductive Development ◽  
Outer Zone ◽  
Mature Embryo ◽  
Globular Embryo ◽  
Primary Endosperm Nucleus ◽  
Oil Glands ◽  
Polygonum Type ◽  
History Of

In Darwinia the floral parts are differentiated in a "calyx-orolla-gynoeciumandroecium" sequence. In individual buds stages of microsporogenesis markedly precede corresponding stages of megasporogenesis. The anther is tetrasporangiate with all sporangia lying in one plane. The secretory tapetum is one- to three-layered within the same microsporangium and a large number of Ubisch bodies are formed. The anthers dehisce by minute lateral pores and an ingenious mechanism helps disperse the twocelled pollen grains. A basal placenta in the single loculus of the ovary bears four ovules in D. micropetala and two in D. fascicularis. In both species, however, only one ovule is functional after fertilization. The fully grown ovules are anatropous, crassinucellar, and bitegmic; the inner integument forms the micropyle. The parietal tissue is most massive at the completion of megasporogenesis but is progressively destroyed later. The embryo sac follows the Polygonum type of developnlent and when mature is five-nucleate, the three antipodals being ephemeral. Following fertilization, the primary endosperm nucleus divides before the zygote. Subsequent nuclear divisions in the endosperm mother cell are synchronous and lead to a free-nuclear endosperm which becomes secondarily cellular, starting from the micropylar end at the time the globular embryo assumes an elongated shape. Embryogeny is irregular and the mature embryo is straight with a massive radicle and a hypocotyl which terminates in two barely recognizable cotyledons. Sometimes the minute cotyledons are borne on a narrow neck-like extension of the hypocotyl. A suspensor is absent. Both integuments are represented in the seed coat and only the outer layer of the outer and the inner layer of the inner integuments, with their thick-walled tanniniferous cells, remain in the fully grown seed. The ovary wall is demarcated into an outer zone containing oil glands surrounded by cells containing a tannin-like substance and an inner zone of spongy parenchyma. In the fruit this spongy zone breaks down completely but the outer zone is retained. The two species of Darwinia, while closely resembling each other in their embryology, differ significantly from other Myrtaceae. However, no taxonomic conclusions are drawn at this stage, pending enquiry into the life history of other members of the tribe Chamaelaucieae.

Early events in the embryo sac after intraspecific and interspecific pollinations in Rhododendron kawakamii and R. retusum

1986 ◽  
Vol 64 (2) ◽  
pp. 282-291 ◽  
Author(s):  
V. Kaul ◽  
J. L. Rouse ◽  
E. G. Williams
Keyword(s):  
Seed Set ◽  
Embryo Sac ◽  
Pollen Tubes ◽  
Interspecific Crosses ◽  
Primary Endosperm Nucleus ◽  
Kalmia Latifolia ◽  
Taxonomic Grouping ◽  
Similarities And Differences ◽  
Normal Fertilization

Early events in the embryo sac of Rhododendron kawakamii and R. retusum have been studied after compatible self-pollinations and eight interspecific crosses, using sectioned ovaries, pistil squashes, and seed-set data. Ovules of Rhododendron kawakamii and R. retusum are anatropous, unitegmic, and tenuinucellate, with a typical eight-nucleate, seven-celled embryo sac. Fertilization normally occurs 4–5 days after pollination. The zygote lays down a callose wall but remains undivided during the first 13–15 days after pollination. The primary endosperm nucleus divides soon after fertilization, and development is cellular ab initio. Crosses of R. kawakamii (♂) with R. santapaui and R. retusum and crosses of R. retusum (♂) with R. kawakamii, R. santapaui, R. ovatum, and R. tashiroi showed apparently normal fertilization in a majority of ovules entered by pollen tubes. In crosses of R. kawakamii (♂) with R. quadrasianum and Kalmia latifolia entry of pollen tubes into ovules was delayed and frequently abnormal. Apart from compatible self-pollinations of R. kawakamii an R. retusum, only the cross of R. kawakamii (♂) with R. santapaui produced healthy seedlings. Of the remaining seven interspecific crosses only three showed significant embryo development in control pistils left to mature in situ. Similarities and differences in the breeding behaviour of R. kawakamii and R. retusum are discussed with reference to their taxonomic grouping within subsection Pseudovireya.

Resolving the Lourinia armata (Claus, 1866) complex with remarks on the monophyletic status of Louriniidae, Monard 1927 (Copepoda: Harpacticoida)

Zootaxa ◽  
2021 ◽  
Vol 5051 (1) ◽  
pp. 346-386
Author(s):  
SÜPHAN KARAYTUĞ ◽  
SERDAR SAK ◽  
ALP ALPER ◽  
SERDAR SÖNMEZ
Keyword(s):  
Comparative Evaluation ◽  
Species Complex ◽  
Detailed Examination ◽  
The Other ◽  
Phylogenetic Position ◽  
Nicobar Island ◽  
Other Hand ◽  
The Family ◽  
Close Relationship ◽  
Almost All

An attempt was made to test if Lourinia armata (Claus, 1866)—as it is currently diagnosed—represents a species complex. Detailed examination and comparisons of several specimens collected from different localities suggest that L. armata indeed represents a complex of four closely related morphospecies that can be differentiated from one another by only detailed observations. One of the four species is identified as Lourinia aff. armata and the other three species are described as new to science and named as Lourinia wellsi sp. nov., L. gocmeni sp. nov., and L. aldabraensis sp. nov. Detailed review of previous species records indicates that the genus Lourinia Wilson, 1924 is distributed worldwide. Ceyloniella nicobarica Sewell, 1940, originally described from Nicobar Island and previously considered a junior subjective synonym of L. armata is reinstated as Lourinia nicobarica (Sewell, 1940) comb. nov. on the basis of the unique paddle-shaped caudal ramus seta V. It is postulated that almost all of these records are unreliable in terms of representing true Lourinia aff. armata described herein. On the other hand, the comparative evaluation of the illustrations and descriptions in the published literature indicates the presence of several new species waiting to be discovered in the genus Lourinia.                 It has been determined that, according to updated modern keys, the recent inclusion of the monotypic genus Archeolourinia Corgosinho & Schizas, 2013 in the Louriniidae is not justified since Archeolourinia shermani Corgosinho & Schizas, 2013 does not belong to this family but should be assigned to the Canthocamptidae. On the other hand, it has been argued that the exact phylogenetic position of the Louriniidae still remains problematic since none of the diagnostic characters supports the monophyly of the family within the Oligoarthra. It has also been argued that the close relationship between Louriniidae and Canthocamptidae is supported since both families share the homologous sexual dimorphism (apophysis) on P3 endopod. The most important characteristic that can possibly be used to define Louriniidae is the reduction of maxilliped.  

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