The embryology of Arceuthobium pusillum

1968 ◽  
Vol 46 (12) ◽  
pp. 1473-1476 ◽  
Author(s):  
F. H. Tainter
Keyword(s):  
Basal Cell ◽  
Embryo Sac ◽  
Sperm Nucleus ◽  
The Other ◽  
Terminal Cell ◽  
Transverse Wall

Megasporogenesis in Arceuthobium pusillum begins in March–April, 19 months after emergence of the pistillate aerial shoots. The embryo sacs are fully developed within 1 month. The first division results in a functional dyad and a nonfunctional dyad. The nucleus in the nonfunctional dyad divides once and the resulting nuclei disintegrate. Meiosis in the functional dyad follows immediately. Development of the embryo sac is of the bisporic Allium type. Staminate and pistillate aerial shoots flower in April–May. Fertilization occurs within several days after pollen has adhered to and germinated on the stigmas of pistillate flowers. One sperm nucleus fuses with the egg nucleus, the other with the polar nuclei. A haustorial extension then elongates downward into the ovarian papilla and becomes filled with a file of endosperm cells. Concurrently a uniseriate layer of endosperm has developed around the zygote. The endosperm then grows to a rather massive size before the zygote begins development. A transverse wall forms after the first division of the zygote. The terminal cell is bisected first, followed by bisection of the basal cell. Succeeding anticlinal and periclinal divisions result in growth of the proembryo. Embryonic protoderm is visible as a distinct tissue by the time the embryo has assumed an ovoid shape. When the seeds are forcibly expelled from their fruits in mid-September, the embryo has four distinct histological zones: protoderm, promeristem, ground meristem, and procambium.

Embryology of Calypso bulbosa. II. Embryo development

1992 ◽  
Vol 70 (3) ◽  
pp. 461-468 ◽  
Author(s):  
Edward C. Yeung ◽  
Sandra K. Law
Keyword(s):  
Cell Division ◽  
Key Words ◽  
Embryo Development ◽  
Basal Cell ◽  
Embryo Sac ◽  
Terminal Cell ◽  
Starch Granules ◽  
Terrestrial Orchid ◽  
Storage Products

Calypso bulbosa is a terrestrial orchid that grows in north temperate regions. After fertilization, the zygote enlarges and grows towards the chalazal end of the embryo sac. An unequal cell division gives rise to a smaller terminal cell and a larger basal cell. A constriction forms in the basal cell. Further growth results in a U-shaped embryo. Two patterns of initial terminal cell division have been observed. In a majority of developing embryos, the terminal cell first divides periclinally and then anticlinally. In approximately 5% of the embryos, the initial division of the terminal cell is anticlinal. Despite differences in early cell division patterns, subsequent embryo development is the same. The suspensor consists of a large, highly vacuolated basal cell and a 4-celled filamentous region. Highly conspicuous starch granules are present within the basal cell of the suspensor. At maturity, the embryo proper is small, consisting of approximately 24 cells and lacking marked differentiation of the apical end. Starch and lipid are the main storage products within the embryo proper. Key words: Calypso orchids, embryo development, suspensor.

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.

Ultrastructural Characteristics of Capillaries Entering and Leaving the Stria Vascularis

1986 ◽  
Vol 95 (3) ◽  
pp. 309-312 ◽  
Author(s):  
Kensuke Watanabe
Keyword(s):  
Horseradish Peroxidase ◽  
Basal Cell ◽  
Stria Vascularis ◽  
The Other ◽  
Spiral Ligament ◽  
Perivascular Spaces ◽  
Basal Cells ◽  
Vascular Flow ◽  
Cell Layers ◽  
Ultrastructural Characteristics

Capillaries entering and leaving the stria vascularis were surrounded by layers of basal cells and fibrocytes. The entering capillaries were surrounded by one or two thin basal cells, while the leaving capillaries were surrounded by four or five thicker and interdigitated basal cell layers. Moreover, the layers surrounding the leaving capillaries persisted further into the spiral ligament. Two kinds of filaments were observed in the basal cells, one thin and the other thick. Capillaries were observed to leak horseradish peroxidase before they entered and after they left the stria vascularis. Although the reaction product of horseradish peroxidase was observed in all perivascular spaces of leaving capillaries, very little or no reaction product was observed around some entering capillaries. It is speculated that the layers of basal cells and fibrocytes around entering and leaving capillaries control the vascular flow out of the stria vascularis, although the layers around leaving capillaries may be more contractile than those around entering capillaries.

CD10, TDAG51, CK20, AR, INSM1, and Nestin Expression in the Differential Diagnosis of Trichoblastoma and Basal Cell Carcinoma

2018 ◽  
Vol 27 (1) ◽  
pp. 19-27 ◽  
Author(s):  
Cem Leblebici ◽  
Buket Bambul Sığırcı ◽  
Canan Kelten Talu ◽  
Sevim Baykal Koca ◽  
Gülben Erdem Huq
Keyword(s):  
Differential Diagnosis ◽  
Basal Cell Carcinoma ◽  
Cell Carcinoma ◽  
Basal Cell ◽  
The Other ◽  
Cytokeratin 20 ◽  
Nestin Expression ◽  
The Difference ◽  
Nevus Sebaceous ◽  
Sensitive Marker

Background. Trichoblastoma (TB) and basal cell carcinoma (BCC) are 2 different neoplasms composed of basaloid cells and have overlapping histopathological features. We compared the immunoexpression of CD10, T-cell death-associated gene 51 (TDAG51), cytokeratin 20 (CK20), androgen receptor (AR), insulinoma-associated protein 1 (INSM1), and nestin for the differential diagnosis of these tumors. Materials and Methods. We assessed a total of 27 BCC and 27 TB cases, including 4 TB lesions in nevus sebaceous and 3 malignant TB lesions for CD10, TDAG51, CK20, AR, INSM1, and nestin expression. Results. Staining for CK20, TDAG51, INSM1, and stromal CD10 was significantly more common in TB cases than in BCC cases ( P < .001). Epithelial CD10 and AR staining was significantly more common in BCC cases than in TB cases ( P < .001). The difference between the groups for nestin staining was not significant ( P > .05). Stromal CD10 staining was the most sensitive marker (96.3%) and INSM1 the least sensitive (55.6%) marker for TB. TDAG51 showed 100% specificity for TB. A larger number of CK20 positive cells was found in the cases associated with nevus sebaceous than in the other TBs. Conclusion. All the selected markers except nestin were useful for the differential diagnosis between TB and BCC. CD10 and TDAG51 were more useful than the other markers. The use of CK20 could be preferred in nevus sebaceous lesions. INSM1 was less effective in highlighting Merkel cells within the lesion than CK20.

Revision of Mesothymbris Evans, 1956, from the Late Triassic of Mount Crosby, Queensland (Hemiptera: Cicadomorpha: Hylicelloidea: Hylicellidae)

Zootaxa ◽  
2019 ◽  
Vol 4629 (3) ◽  
pp. 389-396
Author(s):  
KEVIN J. LAMBKIN
Keyword(s):  
Basal Cell ◽  
The Other ◽  
Late Triassic ◽  
Nominal Species ◽  
South Eastern ◽  
Incertae Sedis ◽  
Generic Composition ◽  
The Status

New specimens and a re-examination of their holotypes have clarified the status of five species of the extinct cicadomorphan family Hylicellidae from the Late Triassic (Norian) Mount Crosby Formation of south-eastern Queensland. All were found to be conspecific, resulting in the following synonymies: Mesothymbris Evans, 1956 (= Triassoscytina Evans, 1956, syn. nov. = (in part) Triassoscytinopsis Evans, 1956, syn. nov.), Mesothymbris perkinsi Evans, 1956 (= Mesothymbris woodwardi Evans, 1956, syn. nov. = Triassoscytina incompleta Evans, 1956, syn. nov. = Triassoscytinopsis stenulata Evans, 1956, syn. nov. = Triassoscytinopsis aberrans Evans, 1956, syn. nov.). The Hylicellidae is still poorly defined as is its generic composition. Mesothymbris, however, is clearly distinct from the other Mount Crosby hylicellids, Hylicella Evans, 1956, and Triassocotis, Evans, 1956, in the quite distal primary fork of R, the angled RA at the point of separation of RA1 with RA2 directed towards the apex of the tegmen, the upright RA1, the shape of the intra-medial cell, and CuA just distal to the basal cell strongly curved and very closely approximating the claval suture. The new synonymies further clarify the composition of the cicadomorphan fauna of the Mount Crosby Formation, which as a result of this and other recent revisions, now comprises 16 nominal species in the Dysmorphoptilidae, Hylicellidae and Mesojabloniidae, as well as three species incertae sedis. In the presence of Dysmorphoptilidae and Hylicellidae, the Mount Crosby cicadomorphan fauna is similar to that of the younger Late Triassic Blackstone Formation at nearby Denmark Hill and Dinmore. It differs significantly, however, in the absence, after 90 years of collecting of 100s of specimens, of any representatives of the Dunstaniidae, Mesogereonidae, or Tettigarctidae, families so characteristic of the Denmark Hill/Dinmore fauna. Whether this difference is biogeographical, ecological, or simply as a result of differential preservation is unknown. 

First female and new species of Phaenicocleus (Hemiptera: Heteroptera: Enicocephalidae) from Sabah and a key to genera of Enicocephalidae without forewing basal cell

Zootaxa ◽  
2011 ◽  
Vol 2913 (1) ◽  
pp. 16
Author(s):  
PETR BAŇAŘ ◽  
PAVEL ŠTYS
Keyword(s):  
New Species ◽  
Basal Cell ◽  
The Other ◽  
Fore Tibia ◽  
Discal Cell ◽  
A New Species

A new species of Enicocephalidae: Enicocephalinae, Phaenicocleus granulosus sp. n. (based on a female), is described from Sabah and compared with the other three species of the genus (based on males). Autapomorphies of the genus (particularly reduced armature of fore tibia and tarsus, interrupted posterior claval vein AA3+4, striking occurrence of large setigerous tubercles the latter shared with Australian Usingeriella) are stressed and partly discussed. A new key to genera of Enicocephalidae with forewing basal cell absent and closed discal cell present is provided.

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.

Embryo and endosperm development in coriander (Coriandrum sativum)

Botany ◽  
2011 ◽  
Vol 89 (4) ◽  
pp. 263-273 ◽  
Author(s):  
Edward C. Yeung ◽  
Steve Bowra
Keyword(s):  
Basal Cell ◽  
Structural Changes ◽  
Cell Lineage ◽  
Endosperm Development ◽  
Coriandrum Sativum ◽  
Terminal Cell ◽  
Primary Endosperm Nucleus ◽  
Cell Degeneration ◽  
Storage Products ◽  
And Storage

Coriander ( Coriandrum sativum L.) seeds are rich in lipids and are potentially important sources of oils for industrial use. The objective of this study was to determine the details of embryo and endosperm development and the sites of storage reserves using microscopy and histochemistry. In coriander, the zygote divides unequally, giving rise to a large basal cell and a smaller terminal cell. Subsequent divisions in the basal cell result in the formation of a suspensor, and divisions in the terminal cell give rise to cells of the embryo proper. A defined cell lineage is absent in the formation of the proembryo. Contrary to other flowering plants, the suspensor persists as the embryo matures and storage products are present within the cytoplasm of the suspensor cells. After fertilization, the primary endosperm nucleus divides rapidly, resulting in a large syncytium of nuclei and cytoplasm. The rapid nuclear divisions occur prior to the first division of the zygote. Cellularization of the endosperm occurs soon after. Within the developing seed, the endosperm can be separated into two main regions, i.e., the “embryo surround region” (ESR) of endosperm and the persistent endosperm. The endosperm cells in these two regions have different cell fates and storage products. In the ESR, the endosperm cells undergo distinct structural changes and are destined to degenerate. These endosperm cells produce a significant amount of polysaccharides and these materials appear to aid in cell separation prior to cell degeneration. At the boundary of the ESR, the endosperm cells are partially degenerated with a large accumulation of lipids. The bulk of the endosperm cells next to the seed coat persist and they are responsible for the production and accumulation of storage lipids and proteins.

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.

Cellularization of the female gametophyte in Ranunculus sceleratus

1989 ◽  
Vol 67 (5) ◽  
pp. 1325-1330 ◽  
Author(s):  
N. N. Bhandari ◽  
P. Chitralekha
Keyword(s):  
Female Gametophyte ◽  
Horizontal Cell ◽  
Embryo Sac ◽  
Cell Plate ◽  
Mitotic Division ◽  
The Other ◽  
Central Vacuole ◽  
Distinct Cell ◽  
Antipodal Cells ◽  
Vertical Cell

Wall formation in Ranunculus sceleratus takes place simultaneously at the micropylar and chalazal poles of the embryo sac. During the last (third) mitotic division resulting in an eight-nucleate embryo sac, three distinct cell plates are formed at either pole. Of the three cell plates, CPI (horizontal), CPE (oblique), and CPIII (vertical), the first two are formed between the separating chromatin masses of the two dividing nuclei. CPIII (vertical cell plate) arises subsequently between the first two plates. CPI (horizontal cell plate) extends perpendicular to the long axis of the embryo sac to separate the central vacuole and one nucleus (polar) from the quartet of nuclei. The other two cell plates extend simultaneously between the three remaining nuclei; CPII (oblique plate) cuts off one of the nuclei while CPIII (vertical cell plate) separates the other two. Consequently, the egg apparatus, central cell with two polar nuclei, and three antipodal cells are formed.

Sign in / Sign up

Export Citation Format

Share Document