scholarly journals Radioautographic visualization of incorporation of lipid precursors into anthers of Muscari comosum (L.) Mili.

2015 ◽  
Vol 46 (2) ◽  
pp. 295-302 ◽  
Author(s):  
Barbara Gabara
Keyword(s):  
Acetic Acid ◽  
Palmitic Acid ◽  
Developmental Stages ◽  
Mevalonic Acid ◽  
Pollen Grains ◽  
Pollen Grain ◽  
Tetrad Stage ◽  
Lipid Precursor ◽  
Mother Cells ◽  
Pollen Grain Wall

Incorporation of the following lipid precursors: DL-mevalonic acid-2 <sup>3</sup>H, <sup>3</sup>H palmitic acid and acetic acid-<sup>3</sup>H sodium salt, into the anther cells of <i>Muscari comosum</i> (L.) Mili. has been investigated. These lipid precursors have been demonstrated to incorporate into pollen mother cells, pollen grains and the tapetum at the consecutive developmental stages. Ali used isotopes are incorporated into the cytoplasm of these cells and in the case of pollen grain the radioactivity of pollen grain wall (mainly composed of sporopellenin) is noticed. The highest radioactivity of pollen grain wall is observed after acetic acid, the lower one after palmitic acid, whereas the lowest uptake of lipid precursor occurs after mevalonic acid. In comparison with tetrad stage the distinct inrease of the cytoplasmic radioactivity of tapetum, which appears to1 accompany the labelling of pollen grain wall, seems to indicate the participation of tapetum in the formation of exine. A possible role of Ubisch bodies in the formation of pollen grain wall is discussed.

scholarly journals Prunus necrotic ringspot virus Early Invasion and Its Effects on Apricot Pollen Grain Performance

2007 ◽  
Vol 97 (8) ◽  
pp. 892-899 ◽  
Author(s):  
Khalid Amari ◽  
Lorenzo Burgos ◽  
Vicente Pallas ◽  
María Amelia Sanchez-Pina
Keyword(s):  
Developmental Stages ◽  
Generative Cell ◽  
Pollen Grains ◽  
Growth Zone ◽  
Pollen Tubes ◽  
Climatic Conditions ◽  
Pollen Grain ◽  
Ringspot Virus ◽  
Prunus Necrotic Ringspot Virus

The route of infection and the pattern of distribution of Prunus necrotic ringspot virus (PNRSV) in apricot pollen were studied. PNRSV was detected both within and on the surface of infected pollen grains. The virus invaded pollen during its early developmental stages, being detected in pollen mother cells. It was distributed uniformly within the cytoplasm of uni- and bicellular pollen grains and infected the generative cell. In mature pollen grains, characterized by their triangular shape, the virus was located mainly at the apertures, suggesting that PNRSV distribution follows the same pattern as the cellular components required for pollen tube germination and cell wall tube synthesis. PNRSV also was localized inside pollen tubes, especially in the growth zone. In vitro experiments demonstrated that infection with PNRSV decreases the germination percentage of pollen grains by more than half and delays the growth of pollen tubes by ≈24 h. However, although PNRSV infection affected apricot pollen grain performance during germination, the presence of the virus did not completely prevent fertilization, because the infected apricot pollen tubes, once germinated, were able to reach the apricot embryo sacs, which, in the climatic conditions of southeastern Spain, mature later than in other climates. Thus, infected pollen still could play an important role in the vertical transmission of PNRSV in apricot.

Coenocytism, ameiosis, and chromosome diminution in intergeneric hybrids in the perennial Triticeae

Genome ◽  
1988 ◽  
Vol 30 (5) ◽  
pp. 766-775 ◽  
Author(s):  
Richard R.-C. Wang
Keyword(s):  
Intergeneric Hybrid ◽  
Chromosome Elimination ◽  
Intergeneric Hybrids ◽  
Pollen Grain ◽  
Unreduced Gamete ◽  
Pollen Mother Cells ◽  
Psathyrostachys Juncea ◽  
Hybrid Plants ◽  
Mother Cells ◽  
Pollen Grain Wall

Three different pathways of ameiotic microsporogenesis were observed in some intergeneric hybrids of the perennial Triticeae grasses. In one of the hybrids between Pseudoroegneria spicata ssp. inermis and Psathyrostachys juncea, pollen mother cells remained as premeiotic interphase cells when the pollen grain wall started to form. The microspores in such an ameiotic plant are presumably unreduced. Coenocyte formation coupled with ameiosis occurred in two hybrid plants of Psathyrostachys huashanica × Secale montanum. Less than 10% of the pollen mother cells had one nucleus. An average of 4.44 nuclei, ranging from 1 to 25 per pollen mother cell, was observed. The nuclei in coenocytes remained unfused when the pollen grain wall was formed. Nucleus splitting followed by cytoplasmic budding or cleavage, possibly a process of chromosome diminution or elimination, replaced meiotic divisions in most of the pollen mother cells in one plant of Leymus angustus × Hordeum bulbosum and two plants of Thinopyrum elongatum × Psathyrostachys juncea. It is evident that these meiotic abnormalities are under genetic control. Probable locations for these genes controlling these phenomena are suggested.Key words: coenocyte, ameiosis, chromosome diminution, chromosome elimination, microsporogenesis, unreduced gamete, polyploidy, intergeneric hybrid.

scholarly journals Abnormal Microspore Development Leads to Pollen Abortion in a Seedless Mutant of ‘Ougan’ Mandarin (Citrus suavissima Hort. ex Tanaka)

2007 ◽  
Vol 132 (6) ◽  
pp. 777-782 ◽  
Author(s):  
Zhiyong Hu ◽  
Min Zhang ◽  
Qigen Wen ◽  
Jie Wei ◽  
Hualin Yi ◽  
...  
Keyword(s):  
Pollen Viability ◽  
Pollen Grains ◽  
Pollen Grain ◽  
Mature Pollen ◽  
Abnormal Development ◽  
Microspore Development ◽  
Wild Type ◽  
Pollen Abortion ◽  
Tetrad Stage ◽  
In The Wild

Seedlessness is of commercial importance in citrus (Citrus L.). Seedless ‘Ougan’ mandarin (C. suavissima) was selected from a bud sport mutation that occurred in ‘Ougan’ mandarin. We analyzed their pollen viability through KI-I2 and FDA staining, and examined the anthers of wild-type (seedy) and seedless mutant ‘Ougan’ mandarin using histological and cytochemical methods to characterize the process of pollen development. No pollen fertility was detected in this mutant. Pollen abortion in anthers of the mutant occurred at the tetrad stage of microspore development, and almost all the tetrads were abnormal. The mutant had heterogeneous microspore populations, including monads, dyads, triads, tetrads, and polyads in the same microsporangium. Pollen grain number per anther of the mutant was 21.9% less than the wild type. Morphology of mature pollen grains using SEM showed that the shape of mature pollen grains from both wild type and mutant is similar, but the microsporangia of the latter contained pollen grains of more variable sizes. At the early mature pollen grain stage, abundant starch grains and lipids appeared in the wild type's pollen, but fewer amounts were observed in the mutant. Moreover, the tapetal cells of the wild type accumulated lipids, but not those of the mutant. Results indicated that the abnormal development of the microspore led to pollen abortion in the mutant, and this could be the reason for its seedlessness. However, the genetic reasons for the aberrant tetrads are not clear and are under investigation.

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>

scholarly journals The Study of Pollen Development in Nine Cultivars of Hazelnut (Corylusavellana)

HortScience ◽  
2005 ◽  
Vol 40 (4) ◽  
pp. 1117A-1117
Author(s):  
Chantalak Tiyayon ◽  
Anita Nina Azarenko
Keyword(s):  
Pollen Development ◽  
Developmental Stages ◽  
Male Gametophyte ◽  
Male Flower ◽  
Pollen Grains ◽  
Corylus Avellana ◽  
Tissue Sections ◽  
Development And Differentiation ◽  
Mother Cells ◽  
Pollen Shed

Pollen development is an important event in plant reproduction. Hazelnut (Corylus avellana) male flower differentiation starts in summer and pollen shed is in the winter. Hazelnut pollen shed can vary up to 3 months between early to late flowering genotypes. Microsporogenesis and microgametogenesis of hazelnut is not well understood. Pollen development and differentiation of nine genotypes, representing early to late blooming cultivars from the National Clonal Germplasm Repository in Corvallis, Ore., were studied. Catkins were collected weekly from Aug. to Nov. 2002. Tissue sections were examined under the light microscope. Microsporogenesis was divided into five stages: archesporial cells, sporogenous cells and parietal layers, pollen mother cells (PMC), tetrads, and microspores. Microgametogenesis was distinguished between young pollen grains (uninucleate) and mature pollen grains (binucleate). On 4 Aug., cultivars were at different developmental stages of microsporogenesis. Early blooming cultivars had PMCs present. Later-blooming cultivars only contained archesporial cells. PMCs were present in all cultivars by 22 Aug. Microspores were observed on 26 Sept. in all cultivars. This study contributes to a better understanding of male gametophyte development in hazelnut, which has increased our ability to correlate hazelnut pollen development with bloom phenology.

scholarly journals Pollen grain expression of osmotic adjustment as a screening method on drought tolerance in several wine and table grape genotypes (Vitis vinifera L.)

2020 ◽  
Vol 12 (4) ◽  
pp. 869-883
Author(s):  
Monica DAVID ◽  
Andrei TIŢA ◽  
Ionela D. TOMA ◽  
Cristina-Magdalena CIOBOTEA ◽  
Mădălina F. BĂNUŢĂ
Keyword(s):  
Water Stress ◽  
Osmotic Adjustment ◽  
Developmental Stages ◽  
Screening Method ◽  
Pollen Grains ◽  
Pollen Grain ◽  
Vitis Vinifera L ◽  
Yield And Quality ◽  
High K ◽  
Grape Varieties

Osmotic adjustment is one of the important mechanisms to adapt to drought and it is the only one which is activated under any level of water stress in the plant cells. Grapevine pollen grains response was tested to osmotic stress in fourteen genotypes, initiated by immersion in 55% or 65% polyethylene glycol solutions without and with addition of potassium chloride, to estimate the expressions of osmotic adjustment. The pollen grain test found differences both in the measurements of projected area cytoplasm and expressions of osmotic adjustment present in the cells. Italian Riesling increased pollen grains cytoplasm in PEG solutions with added KCl much more than other genotypes and had the high values for both expressions of induced and overall osmotic adjustment. The results obtained for expression of induced osmotic adjustment underlined the high K+ accumulation capacity of ‘Italian Riesling’, ‘Burgund mare’ 86 Şt., ‘Muscat d’Adda’ 22 Şt., ‘Muscat Ottonel’ 16 Şt., ‘Pinot gris’ 14 Şt. and ‘Argessis’. The lack of correlation between expressions of induced and intrinsic osmotic adjustment indicated that induced osmotic adjustment expressed by K+ might use different mechanisms that are activated at the time of water stress with different levels of solute accumulation. Because the accumulation of K+ in the cells is important in all developmental stages and, in grape yield and quality, pollen responses to induced osmotic adjustment expressed by K+ could be used as a screening method, for establishing the level of drought sensitivity in the grape varieties under water stress.

scholarly journals 3H-thymidyne incorporation into the microspores and pollen grains nuclei in excised Tradescantia stamens

2015 ◽  
Vol 47 (1–2) ◽  
pp. 163-172 ◽  
Author(s):  
Maria Charzyńska ◽  
Joanna Maleszka
Keyword(s):  
Dna Synthesis ◽  
Generative Cell ◽  
Pollen Grains ◽  
Vegetative Nucleus ◽  
Generative Nucleus ◽  
Tetrad Stage ◽  
Pollen Grain Wall ◽  
Medium Culture

The development of microspores and pollen grains lasts in <i>Tradescantia bracteata in vivo</i> from the tetrad stage to pollen shedding about 14 days. This including 7 days of the microspore life cycle. In stamens excised and placed on a medium the microspores and pollen grains develop normally for at least 3 days. <sup>3</sup>H-thymidine is added into medium culture. DNA synthesis m the microspore nucleus is demonstrated 6 days after tetrad formation so at the end of microspore interphase. During synthesis the nucleus lies at one end of the long axis of the vacuolated microspore. Synthesis ends before migration of the nucleus to the proximal pole of the microspore where mitosis begins. Incorporation of <sup>3</sup>H-thymidine into the generative nucleus is noted in two-celled pollen grains as early as about 24h after the end of microspore division. During DNA synthesis the generative cell is rounded and is still adjacent to the pollen grain wall. DNA synthesis ends before separation of the generative cell from the sporoderm, before the generative nucleus starts to elongate. <sup>3</sup>H-thymidine is not incorporated into the vegetative nucleus in stamens developing <i>in vitro</i>.

scholarly journals RADIOAUTOGRAPHIC LOCALIZATION OF DEOXYTHYMIDINE TRIPHOSPHATE IN TRADESCANTIA POLLEN GRAINS DURING DNA SYNTHESIS

1968 ◽  
Vol 38 (3) ◽  
pp. 509-514 ◽  
Author(s):  
S. T. Takats
Keyword(s):  
Acetic Acid ◽  
Dna Synthesis ◽  
Generative Cell ◽  
Pollen Grains ◽  
Pollen Grain ◽  
Ethanol Acetic Acid ◽  
Dry Emulsion ◽  
Generative Nuclei

Tradescantia pollen grains, isolated during the period of DNA synthesis in the generative cell, accumulate deoxythymidine triphosphate (dTTP)-3H after incubation with thymidine-3H in the presence of millimolar deoxyadenosine. Most of this dTTP-3H was found to resist extraction by the fixative, cold ethanol-acetic acid, and its location was investigated by radioautography with thin, dry emulsion. Substantial binding of dTTP-3H occurred as an artifact; but when nuclei were isolated from the fixed pollen grains by sonication, it was found that they were differentially labeled: generative nuclei contained dTTP-3H, vegetative nuclei did not. This observation is discussed and is interpreted as evidence supporting the idea that thymidine is phosphorylated only in the generative cell of the pollen grain.

scholarly journals Optical and ultrastructural study of the pollen grain development in hermaphrodite papaya tree (Carica papaya L.)

2008 ◽  
Vol 51 (3) ◽  
pp. 539-545 ◽  
Author(s):  
Lídia Márcia Silva Santos ◽  
Telma Nair Santana Pereira ◽  
Margarete Magalhães de Souza ◽  
Pedro Correa Damasceno Junior ◽  
Fabiane Rabelo da Costa ◽  
...  
Keyword(s):  
Carica Papaya ◽  
Generative Cell ◽  
Pollen Grains ◽  
Male Gamete ◽  
Mitotic Division ◽  
Pollen Grain ◽  
Grain Development ◽  
Normal Pattern ◽  
Papaya Tree ◽  
Mother Cells

The objective of this study was to describe the pollen grain development in hermaphrodite papaya tree. The flower buds were collected at different stages of the development and the anthers were treated chemically for observation under optical and electronic transmission microscopes. The pollen grain development followed the normal pattern described for the Angiosperms. The pollen grain development was described from meiocyte to the mature pollen grain. In the microsporogenesis, the microspore mother cells or the meiocytes underwent meiosis giving rise to the tetrads that were enclosed by the calose. Later, the tetrads were released by the dissolution of the calose by calase activity and microspores underwent mitosis. Microgametogenesis was characterized by asymmetrical mitotic division of each microspore giving rise to bi-nucleate pollen grains. The structures similar to the plastids were found in the cytoplasm and close to the nucleus of the generative cell. Gradual degeneration was observed in the tapetum during the male gamete development.

The Ultrastructure and Ontogeny of Pollen in Helleborus Foetidus L

1969 ◽  
Vol 5 (2) ◽  
pp. 459-477
Author(s):  
P. ECHLIN ◽  
H. GODWIN
Keyword(s):  
Electron Density ◽  
Final Stage ◽  
Thick Layer ◽  
Pollen Grains ◽  
Pollen Grain ◽  
Outer Side ◽  
Lateral Expansion ◽  
Helleborus Foetidus ◽  
Thin Electron ◽  
Pollen Grain Wall

The first recognizable elements of the pollen grain wall of Helleborus foetidus are initiated in the cellulosic primexine which is formed immediately outside the microspore cytoplasm while the pollen grains are still in the tetrad configuration and enveloped in a thick layer of callose. Elements of the primexine give rise to the precursors of the rod-like bacula of the mature exine. The bacula increase in electron density due to the rapid deposition of sporopollenin, and begin to expand laterally at the outer side to form the tectum. There follows a lateral expansion on the inner side to form the foot-layer. Further deposition of sporopollenin is continued and all elements of the pollen grain wall expand outwards and laterally as the pollen grain enlarges. The enveloping callose disappears and the pollen grains are free in the thecal cavity. A secondary exine is deposited below the primary exine, particularly around the furrows. Initially this process involves a number of thin electron-transparent lines or lamellae about 4 nm thick that appear to arise from the cytoplasm and provide a locus around which sporopollenin is deposited. As the deposition proceeds, the lamellae thicken and finally merge with each other to form the secondary exine. No sign of the lamellae can be seen in the mature pollen grain wall. Towards the end of secondary exine formation the deposition of sporopollenin does not appear to be centred on thin lamellae, but appears as small granules which gradually coalesce. The secondary exine remains discontinuous in the region of the furrow, but becomes consolidated in the inter-furrow regions. As the pollen grain matures the sporopollenin, which is electron-dense when initially deposited, becomes progressively less so. The final stage in development is the deposition of the cellulosic intine, which forms inside the secondary exine and is associated with increased dictyosome activity and randomly oriented microtubules.

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