scholarly journals Microsporogenesis, Macrosporogenesis, and Development of the Macrogametophyte and Seeds of Duboisia Leighhardtii (F.v.M.) and D. Myoporoides (R.Br.)

1949 ◽  
Vol 2 (3) ◽  
pp. 241 ◽  
Author(s):  
C Barnard
Keyword(s):  
Pollen Tube ◽  
Embryo Sac ◽  
Pollen Grains ◽  
Vegetative Nucleus ◽  
Generative Nucleus ◽  
Haploid Number ◽  
Starch Grains ◽  
The Family

In Duboisia Leichhardtii and D. myoporoides macrosporogenesis and the development of the embryo-sac are similar to the descriptions reported for other genera of the family Solanaceae. The haploid number of chromosomes in both species is 30. A generative and vegetative nucleus is formed in each micros pore which later becomes filled with starch grains and uninucleate as a result of degeneration of the vegetative nucleus. At maturity the pollen grains are devoid of starch and are uninucleate. Division of the generative nucleus to form two male nuclei presumably occurs just prior to the discharge of the pollen tube.

scholarly journals Tradescantia bracteata pollen in vitro: pollen tubes development and mitosis

2015 ◽  
Vol 46 (4) ◽  
pp. 587-598 ◽  
Author(s):  
E. Lewandowska ◽  
M. Charzyńska
Keyword(s):  
Pollen Tube ◽  
Generative Cell ◽  
Metaphase Plate ◽  
Pollen Grains ◽  
Neutral Red ◽  
Generative Nucleus ◽  
Mitotic Spindles ◽  
Germinating Pollen ◽  
Vacuolar System

About 90 per cent of <i>Tradescantia bracteata</i> pollen germinates <i>in vitro</i> after 15 min. Mitosis starts in the pollen tube after about 3 h. The mitotic trans-formations of chromosomes within the generative nucleus are not synchronized. They involve succesively the linearly arranged chromosomes in the elongated generative nucleus. In metaphase the chromosomes are arranged tandem-like linearly along the pollen tube. The chromatides translocate in anaphase from various distances to the poles in a plane parallel to the metaphase plate. This suggests that chromosomes have individual mitotic spindles and that coordination of the chromosome transformations in the generative cell is much less strict than in a typical somatic mitosis. Starch is the storage material of pollen grains. In the vegetative cytoplasm of mature pollen grains minute reddish-orange vesicular structures are visible after staining with neutral red. They do not fuse with the vacuoles proper arising in germinating pollen grains to form the vacuolar system of the pollen tube.

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.

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 On the Embryology of Two Species of Genus Lepidium (Brassicaceae)

HortScience ◽  
2018 ◽  
Vol 53 (4) ◽  
pp. 582-588
Author(s):  
Elina Yankova-Tsvetkova ◽  
Ivanka B. Semerdjieva ◽  
Rozalia Nikolova ◽  
Valtcho D. Zheljazkov
Keyword(s):  
Embryo Sac ◽  
Pollen Grains ◽  
Middle Layer ◽  
Reproductive Capacity ◽  
Marginal Lands ◽  
Potential Development ◽  
The Family ◽  
Mature Ovule ◽  
The Stability ◽  
Cultivation Techniques

Some species of genus Lepidium of the family Brassicaceae are ruderal plants, and they can grow well on less fertile soils and may have potential as oilseed crops for marginal lands. To develop cultivation techniques for wild species, the reproductive capacity of the species needs to be revealed. The objective of this work was embryological study of two Lepidium species (L. campestre and L. ruderale). As a result of the study, the main features of male and female generative spheres were established. Male generative sphere: The anther is tetrasporangiate and its wall, the development of which follows the monocotyledonous-type, consists of epidermis, endothecium, one middle layer, and glandular tapetum. Predominantly, tetrahedral microspore tetrads form after simultaneous type of microsporogenesis. The mature pollen grains are two-celled. Female generative sphere: The mature ovule is ana-amphytropous, crassinucellate, and bitegmic with unicellular archesporium that functions as a megaspore mother cell without cutting off of parietal cells. The development of the embryo sac follows the polygonum-type development. The embryo and endosperm develop after the onagrad-type embryogenesis. The established peculiarities of the reproductive biology characterize the studied species as sexually reproducing taxa that guarantee the stability of size of their populations. This is important for the conservation of these species as part of the Bulgarian flora biodiversity given their status of valuable medicinal plants. The data obtained will contribute to the knowledge of the embryological characteristic of genus Lepidium. The results contribute to the understanding of Lepidium biology and potential development of Lepidium species as oilseed cash crops for marginal lands.

scholarly journals Embriología de Erythroxylum havanense Jacq. (Erythroxylaceae)

2017 ◽  
pp. 25
Author(s):  
Sonia Vázquez-Santana ◽  
César A. Domínguez ◽  
Judith Márquez-Guzmán
Keyword(s):  
Seed Coat ◽  
Embryo Sac ◽  
Pollen Grains ◽  
Endosperm Development ◽  
Anther Wall ◽  
Starch Grains ◽  
Reproductive Structures ◽  
Exine Sculpturing ◽  
Erythroxylum Havanense ◽  
Mature Anther

We studied the development of reproductive structures in pin and thrum morphs of Erythroxylum havanense. The young anther wall consists of an epidermis, endothecium , 1-3 middle layers anda binucleate secretory tapetum. The mature anther wall has only two layers: epidermis and endothecium. Microspore tetrads are tetrahedral or isobilateral. Mature pollen grains are tricolporate, bicellular and contain starch grains. Exine sculpturing is verrugate in thrum pollen and reticulate in pin pollen. The ovule is sessile, pendulous, anatropous, bitegmic and crassinucellate. The embryo sac is heptacellular. An endothelium is differentiated. The endosperm development is nuclear, and the basal part of the nucellus persists during early endosperm development. Both integuments form the seed coat.

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>.

Fertilization in Plumbago zeylanica: entry and discharge of the pollen tube in the embryo sac

1982 ◽  
Vol 60 (11) ◽  
pp. 2219-2230 ◽  
Author(s):  
Scott D. Russell
Keyword(s):  
Cell Wall ◽  
Pollen Tube ◽  
Female Gametophyte ◽  
Embryo Sac ◽  
Central Cell ◽  
Vegetative Nucleus ◽  
Egg Cell ◽  
Ultrastructural Organization ◽  
Plumbago Zeylanica ◽  
Male Gametes

The ultrastructural organization of the megagametophyte of Plumbago zeylanica, which lacks synergids, was examined in chemically and physically fixed ovules after entry of the pollen tube. Similar to angiosperms with conventionally organized megagametophytes, the pollen tube enters the ovule through a micropyle, formed by the inner integument, and approaches the female gametophyte by growing between nucellar cells. Unlike other described female gametophytes, however, continued pollen tube growth results in direct penetration of the base of the egg through cell wall projections forming a filiform apparatus and is completed between the egg and central cell without disrupting either of these cells' plasma membranes. A terminal pollen tube aperture forms when the pollen tube reaches an area of strong curvature near the summit of the egg; this results in the release of two sperm cells, the vegetative nucleus, and a limited amount of pollen cytoplasm. The formerly continuous chalazal egg cell wall is locally disrupted near the tip of the pollen tube and apparently is thus modified for reception of male gametes. Discharged pollen cytoplasm rapidly degenerates between the egg and central cell, but unlike pollen tube discharge in conventionally organized megagametophytes, it is unassociated with the degeneraton of any receptor cell within the female gametophyte. Sperm nuclei are transmitted, one to the egg and the other to the central cell, to effect double fertilization by nuclear fusion with their respective female reproductive nuclei. The vegetative nucleus and discharged pollen cytoplasm degenerate between the developing embryo and endosperm during early embryogenesis. The emerging concept that the egg of Plumbago possesses combined egg and synergid functions is supported by the present study and suggests that the megagametophyte of this plant displays a highly specialized egg apparatus composed exclusively of a single, modified egg cell.

scholarly journals Distribution of poly(A)-containing RNA during normal pollen development and during induced pollen embryogenesis in Hyoscyamus niger.

1981 ◽  
Vol 89 (3) ◽  
pp. 593-606 ◽  
Author(s):  
V Raghavan
Keyword(s):  
Transcriptional Activation ◽  
Pollen Grains ◽  
Pollen Embryogenesis ◽  
Vegetative Nucleus ◽  
Generative Nucleus ◽  
Hyoscyamus Niger ◽  
Polyuridylic Acid ◽  
Rna Accumulation ◽  
Rna Formation

The distribution of poly(A)-containing RNA [poly(A)+RNA] in pollen grains of Hyoscyamus niger during normal gametophytic development and embryogenic development induced by culture of anther segments was followed by in situ hybridization with [3H]-polyuridylic acid as a probe. No binding of the isotope occurred in pollen grains during the uninucleate phase of their development. Although [3H]polyuridylic acid binding sites were present in the generative and vegetative cells of maturing pollen grains, they almost completely disappeared from mature grains ready to germinate. During pollen germination, poly(A)+RNA formation was transient and was due to the activity of the generative nucleus, whereas the vegetative nucleus and the sperm cells failed to interact with the applied probe. In cultured anther segments, moderate amounts of poly(A)+RNA were detected in the uninucleate, nonvacuolate, embryogenically determined pollen grains. Poly(A)+RNA accumulation in these grains was sensitive to actinomycin D, suggesting that it represents newly transcribed mRNA. After the first haploid mitosis in the embryogenically determined pollen grains, only those grains in which the generative nucleus alone or along with the vegetative nucleus accumulated poly(A)+RNA in the surrounding cytoplasm were found to divide in the embryogenic pathway. Overall, the results suggest that, in contrast to normal gametophytic development, embryogenic development in the uninucleate pollen grains of cultured anther segments of H. niger is due to the transcriptional activation of an informational type of RNA. Subsequent divisions in the potentially embryogenic binucleate pollen grains appeared to be mediated by the continued synthesis of mRNA either in the generative nucleus or in both the generative and vegetative nuclei.

Effect of Heat Stress During Floral Development on Pollen Tube Growth and Ovary Anatomy in Wheat (Triticum aestivum L.)

1983 ◽  
Vol 10 (2) ◽  
pp. 137 ◽  
Author(s):  
HS Saini ◽  
M Sedgley ◽  
D Aspinall
Keyword(s):  
Heat Stress ◽  
Pollen Tube ◽  
Pollen Tube Growth ◽  
Embryo Sac ◽  
Pollen Grains ◽  
Triticum Aestivum L ◽  
Tube Growth ◽  
Ovary Development ◽  
Abnormal Growth ◽  
Full Complement

Wheat plants (cv. Gabo) otherwise grown at 20°C were subjected to a temperature of 30°C for 3 days at the onset of meiosis in the anthers. Control plants were maintained at 20°C throughout development. Serial sections through the heat-stressed ovaries just prior to anthesis showed that a third contained abnormal embryo sacs. Abnormalities ranged from the complete absence of an embryo sac accompanied by reduced nucellus development, to small embryo sacs that contained the full complement of cells. No abnormalities were observed in control ovaries. Following pollination with fertile pollen, heat-stressed stigmas had similar numbers of germinated pollen grains to non-stressed controls but there were fewer tubes reaching the ovary. In 7% of the stressed pistils, no pollen tube reached the ovary. Callose was deposited in some of the inhibited pollen grains and tubes that showed abnormal growth. It is concluded that heat stress during meiosis in wheat can reduce yield by causing abnormal ovary development, which results in reduced pollen tube growth and seed set.

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