Sexual reproduction in subalpine fir (Abies lasiocarpa)

1981 ◽  
Vol 59 (12) ◽  
pp. 2650-2666 ◽  
Author(s):  
Hardev Singh ◽  
John N. Owens
Keyword(s):  
Female Gametophyte ◽  
Pollen Grains ◽  
Reproductive Phenology ◽  
Abies Lasiocarpa ◽  
Subalpine Fir ◽  
Young Embryo ◽  
Tapetal Cells ◽  
Well Differentiated ◽  
Mother Cells ◽  
Embryonal Mass

Reproductive phenology and anatomy of postdormancy phases of a population of Abies lasiocarpa (Hook.) Nutt. (subalpine fir) from a natural stand near Prince George, B.C., have been studied. The plants exhibited a 1-year type of reproductive cycle. By the end of March, the pollen cones had broken dormancy and contained pollen mother cells (PMC) in premeiotic stages. The PMCs entered meiosis in the 1st week of April and formed tetrads in the 3rd week. The tapetal cells, meanwhile, became binucleate, and then several went through endomitoses. The tapetal cell walls dissolved as the microspores separated from the tetrads. Orbicules were present around the degenerating cytoplasms of tapetal cells. Pollen grains were shed at the five-celled stage in the 3rd week of May.By the end of March, the ovulate cones had also broken dormancy and the ovules contained one to three hypodermal archesporial cells. Initiation of the integument and the formation of megaspore triads were observed in the 3rd week of April. By the 3rd week of May, at the time of pollination, the integument had developed a stigmatic micropylar funnel which received the pollen grains. During the postpollination stages the flange of the funnel became folded, and the nucellus grew up closer to the pollen grains. The nucellar cells at its tip degenerated to form a pollen chamber which contained the pollen grains. Pollen germination, pollen tube growth through the nucellus, and syngamy took only 4–6 days, and occurred at the end of June.The female gametophyte was rather long and narrow and bore two to three archegonia. The proembryo comprised four tiers of four cells each. The first set of suspensors developed from the subterminal tier of cells. The four terminal cells formed the embryonal mass but they contributed unequally. The proximal cells of the embryonal mass formed a massive secondary suspensor. Differentiation of root initials and the initiation of cotyledons in the young embryo took place in the 4th week of July, and the seeds matured in the 3rd week of August. The mature seed comprised a long and well-differentiated embryo, the female gametophyte, most of whose cells were gorged with protein bodies and lipid droplets, and a thick seed coat which was internally differentiated into three tissue layers. The outermost layer of gametophytic cells was devoid of any storage products.

Sexual reproduction in grand fir (Abies grandis)

1982 ◽  
Vol 60 (11) ◽  
pp. 2197-2214 ◽  
Author(s):  
Hardev Singh ◽  
John N. Owens
Keyword(s):  
Pollen Germination ◽  
Apical Meristem ◽  
Pollen Grains ◽  
Root Apical Meristem ◽  
Proximal Pole ◽  
Abies Grandis ◽  
Young Embryo ◽  
Suspensor Differentiation ◽  
Mother Cells ◽  
Embryonal Mass

Phenology and anatomy of the postdormancy reproductive phase of Abies grandis Lindl, were studied. The dormant microsporangia contained compactly arranged pollen mother cells (PMC). The pollen cones broke dormancy in the 3rd week of February and soon afterwards the PMC entered meiosis. Microspore tetrads formed by the 2nd week of March. Pollen grains were shed at the five-celled stage in the 3rd week of April. The pollen grains were bisaccate and showed a triradiate mark on the proximal pole. The dormant ovulate-cone buds bore rudimentary ovuliferous scales, each with two ovular areas. Ovulate cones broke dormancy at the end of January. Megaspore mother cells differentiated by the end of February and the integument was initiated soon afterwards. A megaspore triad formed in the 2nd week of April. By the 3rd week of April, at the time of pollination, the ovule contained a free-nuclear gametophyte, and the integument had developed a stigmatic micropylar funnel. Numerous microdroplets were observed on the surface of the funnel to which pollen adhered. After pollination the funnel became infolded, enclosing the pollen grains. Pollen germination, pollen tube growth through the nucellus, and syngamy took only 3–4 days and occurred in the 3rd week of June. The female gametophyte was long and bore two or three archegonia. The proembryo consisted of four tiers of four cells each. The suspensors developed from the subterminal tier of cells. The four terminal cells formed the embryonal mass, whose proximal cells elongated and developed into a secondary suspensor. Differentiation of the root apical meristem and the cotyledons in the young embryo occurred in the 1st week of July and the embryo matured in the 3rd week of August.

Sexual reproduction of Larix occidentalis

1979 ◽  
Vol 57 (23) ◽  
pp. 2673-2690 ◽  
Author(s):  
John N. Owens ◽  
Marje Molder
Keyword(s):  
Female Gametophyte ◽  
Pollen Grains ◽  
Larix Occidentalis ◽  
Embryo Abortion ◽  
Meristematic Tissue ◽  
Micropylar Canal ◽  
Empty Seed ◽  
Mother Cells ◽  
Pollen Cone ◽  
Female Gametophyte Development

Pollen-cone and seed-cone buds broke dormancy about 2 weeks before vegetative buds on the same tree. Pollen mother cells, which had over-wintered at pachytene or the diffuse stage of meiosis, resumed meiosis and tetrads of microspores were formed by mid-March. Wingless five-celled mature pollen developed by mid-to late April when pollination occurred.When development resumed after dormancy a ring of meristematic tissue formed the integument around the nucellus. The integument tip developed a short abaxial tip and a large adaxial lobe on which developed numerous long stigmatic hairs. A slit-like micropyle remained between the two lips. Several pollen grains usually adhered to the stigmatic hairs and then the two lips grew into the micropyle, engulfing the pollen. No pollination drop was observed. Within the micropylar canal, pollen greatly elongated then formed a pollen tube when the elongated pollen contacted the nucellus.Megaspore mother cells underwent meiosis at the time of pollination. Female gametophyte development, which was the same as in most other members of the Pinaceae, was completed in early June and two to five archegonia were formed. Fertilization occurred in early June, 6 to 8 weeks after pollination. A 16-celled proembryo developed. Simple polyembryony was common but cleavage polyembryony was not observed. Embryo development was similar to other members of the Pinaceae. Embryos and seeds were mature by mid-August.Normal appearing but inviable seed is common in L. occidentalis because the ovule is fully enlarged and the seed coat well developed at fertilization. Inviable seed commonly resulted from the absence of pollination, inviable pollen, lack of fertilization, later ovule abortion, or embryo abortion, primarily during early embryonic stages. Flat empty seed also occurred and resulted from abortion of the megaspore mother cell or early female gametophyte.

Gametogenesis and seed development in Hereroa hesperantha (Dtr.) Dtr. et Schwant (Aizoaceae).

1967 ◽  
Vol 15 (3) ◽  
pp. 425 ◽  
Author(s):  
N Prakash
Keyword(s):  
Female Gametophyte ◽  
Mature Seed ◽  
Anther Wall ◽  
Polygonum Type ◽  
Multinucleate Cells ◽  
Cell Functions ◽  
Innermost Layer ◽  
Tapetal Cells ◽  
Sporadic Cases ◽  
Mother Cells

Hereroa hesperantha belongs to the embryologically little known group of mesembryanthemums. The anther wall is four-layered, the innermost layer constituting the secretory tapetum with multinucleate cells. Prominent Ubisch granules dot the inner tangential and radial walls of the tapetal cells. Cytokinesis in the microspore mother cells is simultaneous, and either tetrahedral or decussate tetrads are formed. The mature pollen is three-celled. The ovules are anacampylotropous, bitegminal, crassinucellar, and non-arillate. The need for employing a uniform terminology for ovular curvature in the Aizoaceae is stressed in view of the existing confusion. The ovules are borne on parietal placentae each of which bears an obturator. The archesporium is one- to many-celled, but only one cell functions. Sporadic cases of double megaspore tetrads and two-nucleate dyad cells were observed. The development of the female gametophyte conforms to the Polygonum type. The synergids and antipedal cells are short-lived. The endosperm is of the Nuclear type and produces a weakly haustorial chalazal caecum. Perisperm takes over the function of endosperm in the mature seed. The embryogeny corresponds to the Solanad type. There is a massive suspensor with some multinucleate cells. The mature seed coat resembles closely that of the Cactaceae and comprises the outer layer of the outer and inner layer of the inner integument, both of which become greatly enlarged and tanniniferous. In features like the presence of staminodes and inferior ovary and the absence of aril, Hereroa differs from other Aizoaceae.

scholarly journals A Contribution to the Embryology of Rhynchelytrum repens (Willd) C.E. Hubbard

1970 ◽  
Vol 7 (7) ◽  
pp. 37-40 ◽  
Author(s):  
Mohammed Inamuddin ◽  
Beatrice Were ◽  
Mohammad Saquib
Keyword(s):  
Mother Cell ◽  
Female Gametophyte ◽  
Pollen Grains ◽  
Middle Layer ◽  
Microspore Mother Cell ◽  
Polygonum Type ◽  
Dense Cytoplasm ◽  
Scientific World ◽  
Tapetal Cells ◽  
Functional Megaspore

The present investigation deals with morphological and embryological studies of Rhynchelytrum repens (Willd) C.E. Hubbard. The development of anther walls are found to be Monocotyledonous type. The tapetal cells are substantially large, glandular and uninucleate. The middle layer is ephemeral and their cells are small in size. It is sandwiched between endothecial and tapetal layer. The endothecial cells are large and develop fibrous thickenings. The microspore mother cell undergoes two successive reduction divisions, giving rise to isobilateral microspore tetrad. The tetrad separates and give rise to four pollen grains. Occasionally, the anther show degenerating pollen grains before dehiscence. Formation of Ubisch's bodies has also been observed. The pollen grains shed at three celled stage. The exine is thick while intine is thin. The ovule is anatropous, bitegmic and crassinucellate. The female archesporial cell becomes large with dense cytoplasm. It directly functions as megaspore mother cell and undergoes two meiotic divisions to produce a linear megaspore tetrad. The micropylar three cells degenerate and chalazal one becomes functional. The chalazal functional megaspore undergoes three mitotic divisions without wall formation and produces 8-nucleate embryosac. Such 8-nucleate embryosac organizes into Polygonum type of embryosac. It is interesting to note that some somatic cells of the ovule undergo nuclear divisions and give rise to facultative apomictic embryosacs. Key Words: Eldoret; Microsporangium; Ubisch's bodies; Facultative apomixis; Female gametophyte. DOI: 10.3126/sw.v7i7.3822 Scientific World Vol.7(7) 2009 pp.37-40

scholarly journals Calcium Distribution during Anther Development in Oil Tea (Camellia oleifera Abel.)

2015 ◽  
Vol 140 (1) ◽  
pp. 88-93 ◽  
Author(s):  
Dongmei Wei ◽  
Chao Gao ◽  
Deyi Yuan
Keyword(s):  
Plasma Membranes ◽  
Pollen Grains ◽  
Anther Development ◽  
Camellia Oleifera ◽  
Calcium Distribution ◽  
Temporal Features ◽  
Tapetal Cells ◽  
Microspore Stage ◽  
Mother Cells ◽  
The Relationship

The mechanism by which calcium regulates anther development remains unclear. This study investigated the relationship between calcium distribution and anther development in oil tea (Camellia oleifera Abel.) by using the potassium antimonite technique. Before the onset of microsporogenesis, abundant minute calcium precipitates appeared on the plasma membranes of microspore mother cells. Meanwhile, numerous precipitates accumulated in the tapetal cells. After meiosis, calcium precipitates appeared in young microspores. During microspore development, calcium precipitates mainly appeared in the small vacuoles of the cytoplasm. At the late microspore stage, a large vacuole formed, and the number of precipitates in the microspore decreased. The number of precipitates in the tapetal cells decreased as microsporogenesis proceeded. Then, calcium precipitates in the bicellular pollen cytoplasm again increased in number. During bicellular pollen development, the number of calcium precipitates decreased. As the pollen grains matured, only a few calcium precipitates were evident in the pollen cytoplasm. The results of this study, which show the spatial and temporal features of calcium distribution during the anther development of C. oleifera, suggest that calcium distribution is related to anther development.

scholarly journals Male meiosis and pollen morphology in diploid Indonesian wild bananas and cultivars

The Nucleus ◽  
2021 ◽  
Author(s):  
Fajarudin Ahmad ◽  
Yuyu S. Poerba ◽  
Gert H. J. Kema ◽  
Hans de Jong
Keyword(s):  
Hybrid Sterility ◽  
Pollen Grains ◽  
Chromosome Analysis ◽  
Male Meiosis ◽  
Enzyme Treatment ◽  
Unreduced Gamete ◽  
Ploidy Levels ◽  
Scientific Disciplines ◽  
Sterile Pollen ◽  
Mother Cells

AbstractBreeding of banana is hampered by its genetic complexity, structural chromosome rearrangements and different ploidy levels. Various scientific disciplines, including cytogenetics, linkage mapping, and bioinformatics, are helpful tools in characterising cultivars and wild relatives used in crossing programs. Chromosome analysis still plays a pivotal role in studying hybrid sterility and structural and numerical variants. In this study, we describe the optimisation of the chromosome spreading protocol of pollen mother cells focusing on the effects of standard fixation methods, duration of the pectolytic enzyme treatment and advantages of fluorescence microscopy of DAPI stained cell spreads. We demonstrate the benefits of this protocol on meiotic features of five wild diploid Musa acuminata bananas and a diploid (AA) cultivar banana “Rejang”, with particular attention on pairing configurations and chromosome transmission that may be indicative for translocations and inversions. Pollen slides demonstrate regular-shaped spores except “Rejang”, which shows fertile pollen grains of different size and sterile pollen grains, suggesting partial sterility and unreduced gamete formation that likely resulted from restitutional meiotic divisions.

CYTOLOGY OF 2n POLLEN FORMATION IN DIPLOID ALFALFA, MEDICAGO SATIVA

1979 ◽  
Vol 21 (4) ◽  
pp. 525-530 ◽  
Author(s):  
Nicholi Vorsa ◽  
E. T. Bingham
Keyword(s):  
Medicago Sativa ◽  
Seed Set ◽  
Pollen Grains ◽  
Genetic Constitution ◽  
2N Pollen ◽  
Diploid Parent ◽  
2N Gamete ◽  
Medicago Sativa L ◽  
Pollen Formation ◽  
Mother Cells

Four diploid (2x) clones of alfalfa, Medicago sativa L., which produced good seed set when used as male parents in 4x-2x crosses were selected for study. The 2x clones descended from 2x haploids of cultivated 4x alfalfa. Fertility in the 4x-2x cross was due to the production of pollen with the unreduced chromosome number (2n pollen) from the 2x parent. The cytological mechanism of 2n pollen formation was found to be disorientation of spindles at metaphase II in up to 38% of the pollen mother cells. Thus, both n and 2n pollen were produced by all four diploids examined. Normal spindles at metaphase II were oriented such that they defined the poles of a tetrahedron and resulted in normal tetrads in a tetrahedral arrangement. Disoriented spindles were basically parallel to each other and resulted in formation of dyads and occasionally a triad. Dyads developed into two 2n pollen grains; triads developed into one 2n and two n pollen grains. Since both n and 2n pollen grains are produced by the diploids, they can be maintained as diploids or they can be used as male parents in crosses to tetraploids. The genetic constitution of 2n pollen resulting from parallel spindles is similar to that expected after first division restitution of meiosis and much of the heterozygosity of the diploid parent is conserved in the gametes. The 2n gamete mechanism has potential application in germplasm transfer and in maximizing heterozygosity in tetraploid hybrids.

scholarly journals Pollen, Tapetum, and Orbicule Development inColletia paradoxaandDiscaria americana(Rhamnaceae)

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
M. Gotelli ◽  
B. Galati ◽  
D. Medan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Pollen Grains ◽  
Pollen Grain ◽  
Ultrastructural Changes ◽  
Transmission Electron ◽  
The Family ◽  
Tapetal Cells ◽  
Grain Formation

Tapetum, orbicule, and pollen grain ontogeny inColletia paradoxaandDiscaria americanawere studied with transmission electron microscopy (TEM). The ultrastructural changes observed during the different stages of development in the tapetal cells and related to orbicule and pollen grain formation are described. The proorbicules have the appearance of lipid globule, and their formation is related to the endoplasmic reticulum of rough type (ERr). This is the first report on the presence of orbicules in the family Rhamnaceae. Pollen grains are shed at the bicellular stage.

scholarly journals Dynamics of Polysaccharides and Neutral Lipids during Anther Development in Castor (Ricinus communis)

2015 ◽  
Vol 140 (4) ◽  
pp. 356-361 ◽  
Author(s):  
Dongmei Wei ◽  
Huimin Xu ◽  
Ruili Li
Keyword(s):  
Neutral Lipids ◽  
Ricinus Communis ◽  
Starch Content ◽  
Single Layer ◽  
Pollen Grains ◽  
Middle Layer ◽  
Anther Development ◽  
Anther Wall ◽  
Starch Grains ◽  
Tapetal Cells

Anthers contain starch and neutral lipids, which have key roles in microspore ontogeny and gametophyte development. In this study, we observed the dynamic changes in starch and neutral lipids in the anther developmental processes of castor (Ricinus communis) by cytochemical methods. Starch grains and neutral lipids presented a regular dynamic distribution during anther development. In young anthers, some neutral lipids accumulated in sporogenous cells, whereas neutral lipids disappeared with microspore growth. At the late microspore stage, starch grains began to accumulate in microspores, and the starch content of bicellular pollen significantly increased after microspore mitosis. At anthesis, starch grains and neutral lipids accumulated in the mature pollen grains. Visible changes occurred in anther wall cells. The epidermis, middle layer, and tapetum were degenerated, and only a single layer of endothecium remained at anthesis. The dynamic variation of starch grains and neutral lipids in tapetal cells was consistent with the changes in microspores and pollen during anther development. All these findings demonstrated that tapetal cells directly interacted with the developing gametophytes. The tapetal cells play an important role in supplying nutritional substances for microspore absorption. Moreover, the endothecium protects the pollen and contributes to anther dehiscence. The results of this study provide a foundation for the further research on sexual reproduction in angiosperms.

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