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 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.

Critical level of radiation damage of root apical meristem and mechanisms for its recovery in Pisum sativum L.

2011 ◽  
Vol 45 (1) ◽  
pp. 18-26 ◽  
Author(s):  
E. A. Kravets ◽  
A. N. Mikheev ◽  
L. G. Ovsyannikova ◽  
D. M. Grodzinsky
Keyword(s):  
Pisum Sativum ◽  
Radiation Damage ◽  
Apical Meristem ◽  
Critical Level ◽  
Root Apical Meristem ◽  
Pisum Sativum L

scholarly journals Sound Waves Promote Arabidopsis thaliana Root Growth by Regulating Root Phytohormone Content

2021 ◽  
Vol 22 (11) ◽  
pp. 5739
Author(s):  
Joo Yeol Kim ◽  
Hyo-Jun Lee ◽  
Jin A Kim ◽  
Mi-Jeong Jeong
Keyword(s):  
Arabidopsis Thaliana ◽  
Cell Division ◽  
Root Growth ◽  
Apical Meristem ◽  
Cell Number ◽  
Root Apical Meristem ◽  
Control Group ◽  
Auxin Signaling ◽  
Ethylene Signaling ◽  
Sound Waves

Sound waves affect plants at the biochemical, physical, and genetic levels. However, the mechanisms by which plants respond to sound waves are largely unknown. Therefore, the aim of this study was to examine the effect of sound waves on Arabidopsis thaliana growth. The results of the study showed that Arabidopsis seeds exposed to sound waves (100 and 100 + 9k Hz) for 15 h per day for 3 day had significantly longer root growth than that in the control group. The root length and cell number in the root apical meristem were significantly affected by sound waves. Furthermore, genes involved in cell division were upregulated in seedlings exposed to sound waves. Root development was affected by the concentration and activity of some phytohormones, including cytokinin and auxin. Analysis of the expression levels of genes regulating cytokinin and auxin biosynthesis and signaling showed that cytokinin and ethylene signaling genes were downregulated, while auxin signaling and biosynthesis genes were upregulated in Arabidopsis exposed to sound waves. Additionally, the cytokinin and auxin concentrations of the roots of Arabidopsis plants increased and decreased, respectively, after exposure to sound waves. Our findings suggest that sound waves are potential agricultural tools for improving crop growth performance.

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 AT-HOOK MOTIF NUCLEAR LOCALISED PROTEIN 18 as a Novel Modulator of Root System Architecture

2020 ◽  
Author(s):  
Marek Šírl ◽  
Tereza Šnajdrová ◽  
Dolores Gutiérrez-Alanís ◽  
Joseph G. Dubrovsky ◽  
Jean Phillipe Vielle-Calzada ◽  
...  
Keyword(s):  
Root System ◽  
System Architecture ◽  
Lateral Root ◽  
Apical Meristem ◽  
Lateral Roots ◽  
Primary Root ◽  
Root System Architecture ◽  
Root Apical Meristem ◽  
Root Initiation ◽  
Lateral Root Initiation

The AT-HOOK MOTIF NUCLEAR LOCALIZED PROTEIN (AHL) gene family encodes embryophyte-specific nuclear proteins with DNA binding activity. They modulate gene expression and affect various developmental processes in plants. We identify AHL18 (At3G60870) as a developmental modulator of root system architecture and growth. AHL18 regulates the length of the proliferation domain and number of dividing cells in the root apical meristem and thereby, cell production. Both primary root growth and lateral root development respond according to AHL18 transcription level. The ahl18 knock-out plants show reduced root systems due to a shorter primary root and a lower number of lateral roots. This change results from a higher number of arrested and non-developing lateral root primordia (LRP) rather than from decreased initiation. Overexpression of AHL18 results in a more extensive root system, longer primary roots, and increased density of lateral root initiation events. Formation of lateral roots is affected during the initiation of LRP and later development. AHL18 regulate root apical meristem activity, lateral root initiation and emergence, which is in accord with localization of its expression.

scholarly journals DNA synthesis in the nuclei of Pinus silvestris embryos during

2015 ◽  
Vol 43 (4) ◽  
pp. 459-464
Author(s):  
P. Brodzki
Keyword(s):  
Dna Synthesis ◽  
Apical Meristem ◽  
Pinus Silvestris ◽  
Vascular Elements ◽  
Mother Cells

DNA synthesis starts earliest in the apical meristem of the shoot, and latest in the cotyledons. Mitoses appear simultaneously in the apical meristem and in the hypocotyl cortex. Synthesis continues in the mother cells of vascular elements and cotyledon parenchyma when mitosis ceases. In the cotyledons DNA synthesis is rather synchronous and leads to the elimination of 2 C nuclei.

scholarly journals Biology of Flowering, Fruit and Viability of Pollen of Varieties and Forms of Quince Cultivated on the Territory of the Nakhchivan Autonomous Republic

2021 ◽  
Vol 7 (3) ◽  
pp. 64-69
Author(s):  
L. Bayramov
Keyword(s):  
Pollen Fertility ◽  
Pollen Germination ◽  
Glucose Solution ◽  
Pollen Viability ◽  
Pollen Grains ◽  
Weather Conditions ◽  
Distilled Water ◽  
Water Control ◽  
Germinated Pollen ◽  
Autonomous Republic

Abstract. The zones of distribution of varieties and forms of quince on the territory of the Nakhchivan Autonomous Republic have been established, phenological observations have been carried out, their flowering and fruiting have been studied. On the territory of the Autonomous Republic, flowering of varieties and forms of quince begins in the second decade of April, depending on the distribution zone, with an average daily temperature of 12–13 °C and lasts 12–13 days, depending on weather conditions. Each flower has 10–12 stamens arranged in one row. The article also studied the viability of pollen in a number of quince varieties. Pollen viability was studied in the varieties Sary, Tursh, Ordubad, Gara and wild forms. Pollen fertility was determined by staining with acetocarmine. Pollen germinates in 2–5–10–15 and 20% glucose solution. Counting of germinated pollen grains was carried out under a microscope. The study showed that of all the experimental varieties, the pollen fertility of the Sary quince and Tursh quince varieties is high (up to 96.6–97.1%). The best medium for the germination of quince pollen is a 10–15% glucose solution. Pollen germination in this solution reaches 47.4–88.0%. In distilled water (control), the germination of quince pollen reached from 9.7% to 35.6% for varieties. Quince pollen remains viable for 31–43 days.

scholarly journals Impact of Manganese on Pollen Germination and Tube Growth in Lily

2021 ◽  
Vol 74 ◽  
Author(s):  
Thomas Sawidis ◽  
Gülriz Baycu ◽  
Elżbieta Weryszko-Chmielewska ◽  
Aneta Sulborska
Keyword(s):  
Pollen Tube ◽  
Pollen Germination ◽  
Surrounding Medium ◽  
Pollen Grains ◽  
Lilium Longiflorum ◽  
Tube Growth ◽  
Low Concentrations ◽  
Main Effect

Abstract In vitro culture of Lilium longiflorum pollen grains was carried out to determine the role of manganese in pollen germination and pollen tube growth. Pollen germination was adversely affected by the presence of manganese (>10 −8 M), whereas low concentrations (10 −12 –10 −10 M) stimulated the process. Manganese caused morphological anomalies during tube growth, characterized by irregular pollen tube thickening and swollen tips. The main effect was the anomalous cell wall formation at the tip, in which the presence of several organelles reduced the number of secretory vesicles. A loose network of fibrillar material and spherical aggregates, mostly in the tip region, was detected, and this material was progressively loosened into the surrounding medium. As a response to potential toxicity, the excess manganese was isolated in vacuoles, which formed an internal barrier against penetration of manganese to the tip area. Elevated manganese concentrations might affect plant reproduction, resulting in anomalies in gamete development. Consequently, the loss in genetic diversity and decreased fruit set ultimately lower yield.

Primary vascular patterns in root meristems of Pontederia cordata and their relevance to studies of root development

1980 ◽  
Vol 58 (12) ◽  
pp. 1351-1369 ◽  
Author(s):  
W. A. Charlton
Keyword(s):  
Apical Meristem ◽  
Vascular System ◽  
Root Apex ◽  
Root Apical Meristem ◽  
Vascular Pattern ◽  
Quiescent Centre ◽  
Vascular Differentiation ◽  
Pontederia Cordata ◽  
Distribution Of Components ◽  
Root Apices

There are several files of metaxylem cells in root apices of Pontederia cordata L., each considered to consist of a series of prospective vessels with their ends in contact. Two longitudinally adjacent vessels may be in the same file of cells produced by the root apex or in adjacent files. As the root grows, successive prospective vessels are added to the apical ends of most of the files but not all files are continued. Addition of prospective vessels appears to take place within the "quiescent centre" of the root apical meristem. Where files are not continued there is no immediate readjustment of remaining files. The longitudinal and transverse distribution of components of the vascular system (including protophloem and protoxylem) is discussed in relation to the means by which the pattern of development may be controlled. Rates of production of vessels and the final lengths of the vessels are estimated. The observations and deductions are discussed in relation to other studies of root growth, vascular differentiation, and vascular pattern formation and maintenance.

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