Permanent odd polyploidy in a grass (Andropogon ternatus)

Genome ◽  
1987 ◽  
Vol 29 (2) ◽  
pp. 340-344 ◽  
Author(s):  
Guillermo A. Norrmann ◽  
Camilo L. Quarín
Keyword(s):  
Meiotic Division ◽  
Daughter Cell ◽  
Diploid Species ◽  
Embryo Sac ◽  
Pollen Grains ◽  
Sperm Nucleus ◽  
The Other ◽  
Breeding Systems ◽  
Egg Cell ◽  
Interspecific Crosses

Andropogon ternatus is a triploid species (2n = 3x = 30) with a striking process of microsporogenesis that leads to the formation of two kinds of pollen grains. One-half of the grains carry only one 10-chromosome genome and the other half carry two genomes. After the first meiotic division in the megaspore mother cell, the micropylar daughter cell always has two nuclei, each with 10 chromosomes (genomes S and T); the chalazal daugher cell has one 10-chromosome set (genome S) and undergoes the second meiotic division giving rise to two megaspores; the one closer to the chalaza is the functional megaspore, while the other degenerates. The two-nucleate micropylar daughter cell remains undivided and then degenerates. Thus, the embryo sac always develops from a megaspore with 10 chromosomes (genome S). The results of interspecific crosses with a taxonomically related diploid species (A. selloanus) as well as the study of pollen grain development suggest that the grains carrying nuclei with 20 chromosomes (genomes ST) are functional in the fertilization process, while those with 10-chromosome nuclei seem to be ineffective. Therefore, A. ternatus is a sexual triploid that accomplishes the stability of its odd polyploid level by transmitting one genome through the egg cell and two genomes through the sperm nucleus. This is the first report of permanent odd polyploidy for a species of the monocotyledons. Key words: Gramineae, Andropogon ternatus, odd polyploidy, female meiosis, breeding systems.

Overgrowth of Pollen Tubes in Embryo Sacs of Rhododendron Following Interspecific Pollinations

1986 ◽  
Vol 34 (4) ◽  
pp. 413 ◽  
Author(s):  
EG Williams ◽  
V Kaul ◽  
JL Rouse ◽  
BF Palser
Keyword(s):  
Pollen Tube ◽  
Embryo Sac ◽  
Pollen Tubes ◽  
Egg Cell ◽  
Interspecific Crosses ◽  
Main Body

Frequent overgrowths of pollen tubes within the embryo sac are characteristic of a number of interspecific crosses in the genus Rhododendron (Ericaceae). The combined techniques of sectioning, squashing and whole-ovule clearing have confirmed that in ovules showing this phenomenon the pollen tube fails to terminate growth and release sperms on entry into a synergid; instead it continues to grow beyond the synergid and egg cell, often filling the main body of the embryo sac with a coiled and distorted mass. Such ovules fail to develop further. The occurrence and possible causes of this error syndrome are discussed.

Apospory in Paspalum thunbergii

2004 ◽  
Vol 52 (1) ◽  
pp. 81 ◽  
Author(s):  
Guohua Ma ◽  
Xuelin Huang ◽  
Nanxian Zhao ◽  
Qiusheng Xu
Keyword(s):  
Chromosome Number ◽  
Developmental Stage ◽  
Pollen Viability ◽  
Paraffin Section ◽  
Embryo Sac ◽  
Low Frequency ◽  
The Other ◽  
Egg Cell ◽  
Successive Generations ◽  
Mother Cells

The cytology, development of aposporous embryo sac, pro-embryo and pseudogamy in Paspalum thunbergii Kunth ex Steud. was studied. P. thunbergii was found to be a tetraploid cytotype, with a chromosome number of 40. Meiosis of the pollen mother cells was irregular, pollen viability was low and multiporate pollens were often observed. Megasporogenesis began normally; however, the megaspore deteriorated at the developmental stage of tetrad, while one to five specific nucellar cells became active and began enlarging, and then developed into aposporous embryo sacs. The mature aposporous sacs usually had three nuclei characterised by one egg cell and two polar nuclei. The egg cell developed spontaneously to form pro-embryos prior to anthesis. When several aposporous sacs occurred in the same ovule, usually one sac near the micropyle was involved in pseudogamy, while the other sacs were not involved. Low frequency of twin-embryo seedlings was observed after seeds matured. Examination of three successive generations by paraffin-section and clearing methods revealed that no sexual sac was present. Therefore, the species P. thunbergii is considered to be an obligate apomict that reproduces by apospory.

scholarly journals Development of generative structures of polar Caryophyllaceae plants: the Arctic Cerastium alpinum and Silene involucrata, and the Antarctic Colobanthus quitensis

2017 ◽  
Vol 38 (1) ◽  
pp. 83-104 ◽  
Author(s):  
Wioleta Kellmann-Sopyła ◽  
Justyna Koc ◽  
Ryszard J. Górecki ◽  
Marcin Domaciuk ◽  
Irena Giełwanowska
Keyword(s):  
Embryo Sac ◽  
Single Layer ◽  
Pollen Grains ◽  
The Arctic ◽  
Egg Cell ◽  
Colobanthus Quitensis ◽  
West Antarctic ◽  
The Family ◽  
Electron Microscopes ◽  
Species Specific

AbstractThe embryology of three polar flowering plants of the family Caryophyllaceae was studied using the methods and techniques of the light, normal and fluorescence microscopes, and the electron microscopes, scanning and transmission. The analyzed species wereColobanthus quitensisof West Antarctic (King George Island, South Shetlands Islands) as well asCerastium alpinumandSilene involucrataof the Arctic (Spitsbergen, Svalbard). In all evaluated species, flowering responses were adapted to the short Arctic and Australian summer, and adaptations to autogamy and anemogamy were also observed. The microsporangia of the analyzed plants produced small numbers of microspore mother cells that were differentiated into a dozen or dozens of trinucleate pollen grains. The majority of mature pollen grains remained inside microsporangia and germinated in the thecae. The monosporous Polygonum type (the most common type in angiosperms) of embryo sac development was observed in the studied species. The egg apparatus had an egg cell and two synergids with typical polarization. A well-developed filiform apparatus was differentiated in the micropylar end of the synergids. In mature diaspores of the analyzed plants of the family Caryophyllaceae, a large and peripherally located embryo was, in most part, adjacent to perisperm cells filled with reserve substances, whereas the radicle was surrounded by micropylar endosperm composed of a single layer of cells with thick, intensely stained cytoplasm, organelles and reserve substances. The testae of the analyzed plants were characterized by species-specific primary and secondary sculpture, and they contained large amounts of osmophilic material with varied density. Seeds ofC. quitensis,C. alpinumandS. involucrataare very small, light and compact shaped.

Embryological studies on hybridization between Theobroma cacao and Theobroma grandiflora

1972 ◽  
Vol 50 (11) ◽  
pp. 2117-2124 ◽  
Author(s):  
Veronica A. Martinson
Keyword(s):  
Theobroma Cacao ◽  
Interspecific Cross ◽  
Embryo Sac ◽  
Egg Cell ◽  
Interspecific Crosses ◽  
Seed Formation ◽  
Contributory Factors ◽  
Poor Seed ◽  
Endosperm Formation ◽  
Species Hybridization

In a comparative study of embryo development in intraspecific (U6 × K5/353) and interspecific (U6 × T33) crosses of Theobroma, the development of the embryo sac as described by previous authors was confirmed. Disintegration of synergids showed that the growth of the pollen through the style was slightly quicker in intraspecific than in interspecific crosses, but the number of embryo sacs which had received male nuclei 3 days after pollination was about the same. Although gametic fusion and endosperm formation in the intraspecific cross was in advance of those in interspecific cross, the major blockage in species hybridization occurred subsequent to fertilization, and in most instances, well after the proembryo stage. Abnormal cell division and cell differentiation were contributory factors to poor seed formation. Possible causes of the abnormality have been discussed.Autonomous enlargement and the binucleate appearance of the egg cells in the unpollinated flower suggested a tendency to parthenogenesis and diploidization of the egg cell, under special conditions. Although a large proportion of the cacao seeds observed in the species crosses are most probably intraspecific seedlings arising from contamination after controlled pollinations, the occurrence of a small number of true maternal seeds cannot be ruled out altogether.

scholarly journals Biology of generative reproduction of Colobanthus quitensis (Kunth) Bartl. from King George Island, South Shetland Islands

2011 ◽  
Vol 32 (2) ◽  
pp. 139-155 ◽  
Author(s):  
Irena Giełwanowska ◽  
Anna Bochenek ◽  
Ewa Gojło ◽  
Ryszard Görecki ◽  
Wioleta Kellmann ◽  
...  
Keyword(s):  
Embryo Sac ◽  
Pollen Grains ◽  
South Shetland Islands ◽  
Egg Cell ◽  
Strong Wind ◽  
King George Island ◽  
Natural Conditions ◽  
Shetland Islands ◽  
Colobanthus Quitensis ◽  
The Antarctic

Biology of generative reproduction of Colobanthus quitensis (Kunth) Bartl. from King George Island, South Shetland Islands Our macroscopic observations and microscopic studies conducted by means of a light microscope (LM) and transmission electron microscope (TEM) concerning the re-production biology of Colobanthus quitensis (Caryophyllaceae) growing in natural conditions in the Antarctic and in a greenhouse in Olsztyn (northern Poland) showed that this plant develops two types of bisexual flowers: opening, chasmogamous flowers and closed, cleistogamous ones. Cleistogamy was caused by a low temperature, high air humidity and strong wind. A small number of microspores differentiated in the microsporangia of C. quitensis, which is typical of cleistogamous species. Microsporocytes, and later microspores, formed very thick callose walls. More than twenty spheroidal, polypantoporate pollen grains differentiated in the microsporangium. They germinated on the surface of receptive cells on the dry stigma of the gynoecium or inside the microsporangium. A monosporic embryo sac of the Polygonum type differentiated in the crassinucellar ovule. During this differentiation the nucellus tissue formed and stored reserve materials. In the development of generative cells, a male germ unit (MGU) with differentiated sperm cells was observed. The smaller cell contained mainly mitochondria, and the bigger one plastids. In the process of fertilization in C. quitensis only one nucleus of the sperm cell, without cytoplasm fragments, entered the egg cell, and the proembryo developed according to the Caryophyllad type. Almost all C. quitensis ovules developed and formed perispermic seeds with a completely differentiated embryo both under natural conditions in the Antarctic and in a green-house in Olsztyn.

scholarly journals Breeding Systems in tetraploid Rubus species

1966 ◽  
Vol 7 (2) ◽  
pp. 245-253 ◽  
Author(s):  
G. J. Dowrick
Keyword(s):  
Chromosome Number ◽  
Embryo Sac ◽  
Breeding Systems ◽  
Egg Cell ◽  
Breeding Behaviour ◽  
Rubus Species ◽  
Embryo Sac Formation ◽  
Mother Cells ◽  
Normal Meiosis

1. The breeding behaviour of the three tetraploid Rubus species R. caesius, R. calvatus and R. laciniatus (2n = 28) has been investigated.2. Megaspore mother cells of all three species always undergo a normal meiosis and embryo-sac formation is of the Polygonum type. Egg cells have fourteen chromosomes.3. There is no evidence for the production of either aposporic or diplosporic embryo-sacs as has previously been assumed.4. The proportion of sexual and apomictic progeny differs in the three species and, in R. laciniatus, varies according to the chromosome number of the pollinating parent.5. The apomictic progeny are produced by diploidization of the reduced egg cells. These diploidized egg cells can subsequently be fertilized in R. laciniatus.6. The versatility in the breeding behaviour of these species is explained on the basis that only one type of embryo-sac is formed and that the developmental behaviour of the egg cell is conditioned by the chromosome number of the pollinating parent. Apomixis in these species is not a consequence of a breakdown of meiosis.

Development of diploid pollen in spikelet cultures of barley (Hordeum vulgare L.) and rye (Secale cereale L.)

2004 ◽  
Vol 52 (1) ◽  
pp. 1-8 ◽  
Author(s):  
É. Szakács ◽  
B. Barnabás
Keyword(s):  
Hordeum Vulgare ◽  
Secale Cereale ◽  
Pollen Grains ◽  
Colchicine Treatment ◽  
Root Tip ◽  
Egg Cell ◽  
Interspecific Crosses ◽  
Seed Setting ◽  
Hordeum Vulgare L

Colchicine is a plant alkaloid, known for thousands of years and currently used widely for the doubling of the genome in plant and animal cells due to its antimitotic effect. The aim of the present experiments was to develop stable autodiploid pollen grains in vitro in diploid lines of rye (Secale cereale L.) and barley (Hordeum vulgare L.) and to use these in intra- and interspecific crosses. Spikelet cultures of one rye and one barley variety were subjected to colchicine treatment in different stages of development and under differing in vitro conditions. Exposure to colchicine led to a drastic reduction both in the number of fertile pollen grains and in the percentage seed-setting, which was only observed in cultures inoculated in the early binuclear microspore stage. On medium containing colchicine the seed-setting percentage was 1.6% for barley and 0.1% for rye. Flow cytometry and root tip analysis revealed that all the progeny barley plants were diploid, while in the case of rye one was tetraploid, indicating that the egg cell may also be diploidised by colchicine treatment.

Pollination.

2021 ◽  
Author(s):  
Vicki Cottrell
Keyword(s):  
Abiotic Factors ◽  
Embryo Sac ◽  
Pollen Grains ◽  
Fruit Production ◽  
Pollen Grain ◽  
Egg Cell ◽  
Dispersal Mechanism ◽  
Haploid Male ◽  
Sterile Pollen ◽  
Pollen Formation

Abstract Pollination of flowers is the transfer of pollen grains (haploid male spores) from the anther (part of the androecium) to the stigma (part of the gynoecium) by biotic or abiotic factors (Sliwinska and Bewley, 2014). For seed and fruit production of agricultural crops the main pollinating agents are wind and insects (George, 2011). After a pollen grain is transferred to a receptive stigma, it absorbs water from the stigma surface and germinates. A pollen tube then grows down into the stigma, through the gynoecium and through the apical micropyle; from there it grows into an ovule in the ovary and double fertilisation then takes place. Two sperm are released into the embryo sac; one fertilises the ovule to produce a diploid zygote, and the other joins with two polar nuclei in the ovule to produce a triploid nucleus that will then develop into the nutrient-rich endosperm (Willmer, 2011). Pollen grain diameter is usually in the range 20-70 μm, and the surface structure and morphology varies considerably between plant species and dispersal mechanism (Wiltshire, 2010). Air temperature can have an effect on pollen formation and viability, with high temperatures potentially leading to sterile pollen (Bosland and Votava, 2012). Irradiated pollen grains are still able to germinate and produce pollen tubes that reach the ovule (Germana, 2012). Although they are unable to fertilise the egg cell, this process induces parthenogenesis and has been widely used to produce haploid fruits (Germana, 2012).

scholarly journals Embryology and cytogenetics of Eupatorium pauciflorum and E. intermedium (Compositae)

1998 ◽  
Vol 21 (4) ◽  
pp. 507-514 ◽  
Author(s):  
Maristela Sanches Bertasso-Borges ◽  
James Robert Coleman
Keyword(s):  
Embryo Sac ◽  
Pollen Grains ◽  
Endosperm Development ◽  
Egg Cell ◽  
Pollen Production ◽  
Polygonum Type ◽  
Total Absence ◽  
Basic Set ◽  
Autonomous Endosperm ◽  
Germinated Pollen

The embryology of Eupatorium pauciflorum indicates diplospory with autonomous endosperm development. The embryo sac is of the polygonum type and the polar nuclei mostly fuse before anthesis. The occurrence of precocious embryo and endosperm development in unopened florets, and the total absence of germinated pollen grains on exposed stigmas, as well as the absence of pollen tubes in the ovules, indicate agamospermy to be obligate and embryo and endosperm development autonomous. The study of microsporogenesis revealed the total absence of pollen production in consequence of microsporocyte degeneration before the onset of meiosis, which resulted in absolute male sterility. E. pauciflorum was demonstrated to be an autotriploid with a basic set of 10 chromosomes, each represented three times. Embryological studies showed E. intermedium to undergo reductive meiosis with tetrad formation during megasporogenesis, followed by monosporic embryo sac development of the polygonum type. The polar nuclei fuse before anthesis. The egg cell invariably attains anthesis still undivided, without precocious embryony. Meiosis of microsporogenesis results in the regular formation of 10 bivalents and the subsequent stages of microsporogenesis are normal. Stigmatic loads indicate the regular occurrence of pollination with viable, functional grains. Karyotypic studies revealed a complement of 20 chromosomes separable into 10 pairs. It is concluded that E. pauciflorum, as represented by the material studied, is apomictic while E. intermedium is sexual.

Development of the Anther and Ovule in Capsicum L

1978 ◽  
Vol 26 (3) ◽  
pp. 433 ◽  
Author(s):  
P Dharamadhaj ◽  
N Prakash
Keyword(s):  
Pollen Fertility ◽  
Embryo Sac ◽  
Pollen Grains ◽  
The Other ◽  
Flower Buds ◽  
Viable Pollen ◽  
Male And Female

The structure of the anther and ovule and the development of the male and female gametophytes have been studied in seven cultivated varieties of Capsicum-C. annuum L. var. acuminatum Fingerh. (long red cayenne), C. annuum L. cv. Floral Gem, C. annuum L, var. grossum (L.) Sendt. (giant bell), C. annuum var. longum (DC.) Sendt. (long sweet yellow), C. baccatum L. var. pendulum (Willd.) Eshbaugh, C. frutescens L, var. baccatum (L.) Irish and C. frutescens L, cv. Tabasco. Marked differences in the development were observed between flower buds formed in summer and in winter. In the anthers of winter flower buds of C. annuum var, acuminatum the pollen grains show nuclear multiplication and pollens with all nuclear numbers between two and eight are represented. However, 'pollen embryo sacs' as such are not formed. The normal viable pollen grains are binucleate. The pollen fertility in summer is 93.6% while in winter, on the same plants, it is only 31.3 %. In the development of the ovule there are no marked differences amongst the varieties except in size. Coexistence of mono-, bi- and tetrasporic embryo sac developments has been found in C. annuum var. acuminatum in which monospory is dominant in summer but bispory in winter. Monosporic and bisporic embryo sacs coexist in C. baccatum var. pendulum and C. frutescens var. baccatum. The other varieties show only monosporic development.

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