Sexual reproduction of Larix occidentalis

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.

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Megagametogenesis, fertilization, and embryo development in Larixdecidua

Canadian Journal of Forest Research ◽

10.1139/x86-230 ◽

1986 ◽

Vol 16 (6) ◽

pp. 1301-1309 ◽

Cited By ~ 11

Author(s):

Grzegorz Kosiński

Keyword(s):

Cell Wall ◽

Sexual Reproduction ◽

Mother Cell ◽

Megaspore Mother Cell ◽

Female Gametophyte ◽

Nuclear Stage ◽

Empty Seed ◽

Development Failure ◽

Major Factors ◽

Female Gametophyte Development

The phenology of sexual reproduction in Larixdecidua Mill, varies from year to year, and some intra- and inter-clonal differences were also found. Megaspore mother cell meiosis occurred at the time of pollination, during the second half of April, resulting in three or four megaspores. The free nuclear stage and cell wall and archegonia formation were completed in late May and the first half of June. An average of four archegonia was observed in each ovule, but the number ranged from two to six. Fertilization occurred during the first 20 days of June, about 7 weeks after pollination. A four-tiered, 16-celled proembryo formed. Meristematic regions formed in the embryo from the end of June to mid-July. Fully developed embryos were observed in mid-August. Simple polyembryony and delayed cleavage polyembryony were observed. Lack of pollination, disturbances during megasporogenesis and female gametophyte development, failure of fertilization, and embryo degeneration are the major factors resulting in empty seed.

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Anther and Ovule Development in Tasmannia (Winteraceae)

Australian Journal of Botany ◽

10.1071/bt9920877 ◽

1992 ◽

Vol 40 (6) ◽

pp. 877 ◽

Cited By ~ 19

Author(s):

N Prakash ◽

AL Lim ◽

FB Sampson

Keyword(s):

Mother Cell ◽

Female Gametophyte ◽

Cell Plate ◽

Basic Type ◽

Ovule Development ◽

Linear Tetrad ◽

Polygonum Type ◽

Secretory Type ◽

Mother Cells ◽

Female Gametophyte Development

Three species of Tasmannia R.Br. ex DC., T. glaucifolia, T. insipida and T. stipitata are studied. The anther is tetrasporangiate and its waU development conforms to the Basic type. The tapetum follows the secretory type of development. Cytokinesis in the microspore mother cells is simultaneous but an evanescent cell plate is present at telophase I and anaphase I1 during meiosis. Pollen tetrads are permanent and tetrahedral. The mature pollen is anaulcerate, reticulate and 2-celled. The ovule. is anatropous, bitegmic and crassinucellate. The micropyle in T. stipitata and T. Glaucifolia is formed by the inner integument only whereas in T. insipida it is formed by both the integuments and is zigzag in outline. Meiosis in the single megaspore mother cell produces a linear or T-shaped megaspore tetrad in T. stipitata and T. glaucifolia but only a linear tetrad in T. insipida. Female gametophyte development is of the monosporic Polygonum type. Fertilisation is porogamous; triple fusion and syngamy occur simultaneously.

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Pollination, female gametophyte, and embryo and seed development in yellow cedar (Chamaecyparis nootkatensis)

Canadian Journal of Botany ◽

10.1139/b75-024 ◽

1975 ◽

Vol 53 (2) ◽

pp. 186-199 ◽

Cited By ~ 18

Author(s):

John N. Owens ◽

Marje Molder

Keyword(s):

Seed Development ◽

Female Gametophyte ◽

Pollen Tubes ◽

Variable Number ◽

Male Gametes ◽

Seed Cone ◽

Complex Forms ◽

The One ◽

Mother Cells ◽

Female Gametophyte Development

After dormancy, both pollen- and seed-cone buds resume development early in April at higher elevations on Vancouver Island. Pollen, formed the previous fall, is shed at the one-celled stage during the last half of April. Pollination occurs during a 2-week period. Pollen frequently germinates and elongates in the pollination drop within the micropyle before reaching the nucellus. Pollen tubes penetrate most of the nucellus during May and early June, then pollen-tube growth slows or stops until mid-July when the pollen tubes quickly extend to the surface of the neck cells and two large, equal-sized male gametes form. Meiosis of the megaspore mother cells occurs during April and early May. Female gametophyte development, similar to that in other members of the Cupressaceae, occurs from late May until late July. An archegonial complex forms with an average of nine archegonia. Fertilization occurs at the end of July and proembryo development begins immediately. A file of four free nuclei forms. Considerable variation exists in subsequent nuclear divisions and cell-wall formation. This may result from the long, narrow archegonia and highly variable number of archegonia. A four-tiered proembryo forms and cleavage polyembryony occurs. The embryos reach the multicellular or the massive stage with secondary suspensors by October when the cones, containing ovules which were pollinated in April, become dormant. Embryo and seed development resume the next April, 1 year after pollination, and development is usually complete in July or August. Embryo development occurs more rapidly near sea level but is complete by fall of the year after pollination at all elevations studied. Most seed is shed early in the fall, but some seed may not be shed until January. The distinction is made between immature 1-year-old and mature 2-year-old seeds and cones. Cones contained an average of 7.2 seeds, of which only 29% were filled.

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REPRODUCTIVE BIOLOGY OF TWO EDIBLE HONEYSUCKLES [Lonicera edulis Turcz. ex Freyn., Lonicera kamtchatica (Sevast.) Pojark.] IN THE CONDITIONS OF SOUTHWESTERN SLOVAKIA

Acta Scientiarum Polonorum Hortorum Cultus ◽

10.24326/asphc.2020.3.6 ◽

2020 ◽

Vol 19 (3) ◽

pp. 63-72

Author(s):

Ľuba Ďurišová ◽

Tünde Juríková ◽

Pavol Jr Eliáš ◽

Jiří Mlček

Keyword(s):

Female Gametophyte ◽

Pollen Grains ◽

Reproductive Organs ◽

Climatic Conditions ◽

Pollen Grain ◽

Flower Initiation ◽

Winter Dormancy ◽

Normal Appearance ◽

Male And Female ◽

Female Gametophyte Development

The formation and development of reproductive organs and fruits was examined for two edible honeysuckle species Lonicera edulis Turcz. ex. Freyn. and Lonicera kamtchatica (Sevast.) Pojark. ‘Gerda’ using cytological and embryological methods. We found out that the flower initiation has began during June in the conditions of southwestern Slovakia. Male and female archespores were differentiated before entering winter dormancy. In most cases we have observed normally developed tetrads, normal appearance of microspores, two-celled polen grains and mature pollen grain. In both species a sufficient amount of normally developed pollen grains was observed. Disturbances during female gametophyte development occurred occasionally, most mature ovules contained 7 cells female gametophyte. Our research pointed to fact that the species are protogynous. Flowering usually takes place in the first half of April. The fruits were mature in the second half of May. We have found that 10 to 11 fully developed seeds have evolved in the fruits of both representatives of Lonicera on average. The above results show the suitability of L. edulis and L. kamtchatica cultivation in SW Slovakia with a relatively low risk of fruit loss due to climatic conditions.

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Sexual reproduction in subalpine fir (Abies lasiocarpa)

Canadian Journal of Botany ◽

10.1139/b81-317 ◽

1981 ◽

Vol 59 (12) ◽

pp. 2650-2666 ◽

Cited By ~ 14

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.

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Sexual reproduction of Sitka spruce (Picea sitchensis)

Canadian Journal of Botany ◽

10.1139/b80-113 ◽

1980 ◽

Vol 58 (8) ◽

pp. 886-901 ◽

Cited By ~ 17

Author(s):

John N. Owens ◽

Marje Molder

Keyword(s):

Sexual Reproduction ◽

Female Gametophyte ◽

Seed Set ◽

Mature Female ◽

Picea Sitchensis ◽

Contributing Factors ◽

Embryo Abortion ◽

Male And Female ◽

Cell Divisions ◽

Mother Cells

The phenology of sexual reproduction of Picea sitchensis (Bong.) Carr. was similar at the three sites on Vancouver Island, British Columbia, used in the study. As indicated by cell divisions, cone buds ended dormancy in early March, 2 weeks before dormancy ended in vegetative buds. Pollen mother cells underwent meiosis in mid-March and mature, saccate, four- or five-celled pollen was formed by late April. Megaspore mother cells underwent meiosis in late March and mature female gametophytes were developed by late May. Pollination occurred in late April. A pollination drop was produced by the nucellus and exuded between the two micropylar arms and pollen was drawn down into a nucellar depression where pollen germinated in late April. Fertilization occurred in early June and early stages of embryo development occurred by late June, 9 weeks after pollination. Cotyledons were initiated in late July and seed was mature by mid-August and shed during the early fall.Development of male and female gametophytes and embryos was similar to patterns shown for other species of Picea. In this study seed set was very poor and resulted primarily from a lack of pollination. Other contributing factors were female gametophyte abortion before fertilization, embryo abortion during early development, and insect damage.

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Bud development in Larix occidentalis. II. Cone differentiation and early development

Canadian Journal of Botany ◽

10.1139/b79-194 ◽

1979 ◽

Vol 57 (14) ◽

pp. 1557-1572 ◽

Cited By ~ 8

Author(s):

John N. Owens ◽

Marje Molder

Keyword(s):

Shoot Elongation ◽

Larix Occidentalis ◽

Short Shoot ◽

Bud Development ◽

Seed Cone ◽

Long Shoots ◽

Short Shoots ◽

Old Trees ◽

Mother Cells ◽

Pollen Cone

The time and method of cone-bud differentiation and the phenology of cone-bud development were studied in 10- to 20-year-old trees growing outside their natural range and three 50-year-old trees growing within their natural range.Both pollen-cone and seed-cone buds of western larch (Larix occidentalis Nutt.) normally differentiated on short shoots that were at least 1 year old. Pollen-cone buds were commonly on proximal nonvigorous, often pendant vegetative long shoots in lower regions of the crown, whereas seed-cone buds were usually found on distal short shoots on vigorous but less pendant vegetative long shoots in upper regions of the crown.All potential cone buds were indistinguishable from potential vegetative short shoot buds during bud-scale initiation. In early June, when vegetative short shoots had begun to initiate leaves, cone-bud apices entered a period of differentiation during which time the mitotic frequency of the apices greatly increased followed by a marked increase in apical size. During differentiation, pollen-cone apices did not initiate any basal foliar organs and a short stalk resulted at the base of the cone, whereas seed-cone apices initiated a few basal foliar primordia before bract initiation began. Microsporophyll initiation began during the last half of June and initiation occurred rapidly until the end of July. Micros porangial development occurred from August to late October when fully developed pollen-cone buds became dormant. Pollen mother cells began meiosis before dormancy and overwintered at the diffuse stage. Bract initiation began about the end of June, was rapid until mid-August, then continued more slowly until seed-cone buds became dormant in late October. Ovuliferous scales were initiated acropetally from mid-August until dormancy. Cone-bud differentiation occurred at about the end of the period of vegetative lateral long shoot elongation at all locations.

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The mac1 Gene: Controlling the Commitment to the Meiotic Pathway in Maize

Genetics ◽

10.1093/genetics/142.3.1009 ◽

1996 ◽

Vol 142 (3) ◽

pp. 1009-1020 ◽

Cited By ~ 3

Author(s):

William F Sheridan ◽

Nadezhda A Avalkina ◽

Ivan I Shamrov ◽

Tatyana B Batyea ◽

Inna N Golubovskaya

Keyword(s):

Female Gametophyte ◽

Embryo Sac ◽

Flowering Plants ◽

Normal Female ◽

Ovule Development ◽

Partial Sterility ◽

Embryo Sac Formation ◽

Female Gametophyte Development ◽

Normal Meiosis ◽

Pleiotropic Mutation

Abstract The switch from the vegetative to the reproductive pathway of development in flowering plants requires the commitment of the subepidermal cells of the ovules and anthers to enter the meiotic pathway. These cells, the hypodermal cells, either directly or indirectly form the archesporial cells that, in turn, differentiate into the megasporocytes and microsporocytes. We have isolated a recessive pleiotropic mutation that we have termed multiple archesporial cells1 (macl) and located it to the short arm of chromosome 10. Its cytological phenotype suggests that this locus plays an important role in the switch of the hypodermal cells from the vegetative to the meiotic (sporogenous) pathway in maize ovules. During normal ovule development in maize, only a single hypodermal cell develops into an archesporial cell and this differentiates into the single megasporocyte. In macl mutant ovules several hypodermal cells develop into archesporial cells, and the resulting megasporocytes undergo a normal meiosis. More than one megaspore survives in the tetrad and more than one embryo sac is formed in each ovule. Ears on mutant plants show partial sterility resulting from abnormalities in megaspore differentiation and embryo sac formation. The sporophytic expression of this gene is therefore also important for normal female gametophyte development.

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

The Nucleus ◽

10.1007/s13237-021-00350-7 ◽

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.

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