Sexual reproduction of Sitka spruce (Picea sitchensis)

1980 ◽  
Vol 58 (8) ◽  
pp. 886-901 ◽  
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.

Sexual reproduction in western red cedar (Thuja plicata)

1980 ◽  
Vol 58 (12) ◽  
pp. 1376-1393 ◽  
Author(s):  
John N. Owens ◽  
M. Molder
Keyword(s):  
Sexual Reproduction ◽  
Seed Production ◽  
Low Temperatures ◽  
Female Gametophyte ◽  
Seed Set ◽  
Thuja Plicata ◽  
Insect Damage ◽  
Red Cedar ◽  
Pollination Drop ◽  
Micropylar Canal

Pollen cones and seed cones ended dormancy in mid-February, microsporogenesis occurred in late February, and pollination occurred for about 1 week in early March. Pollen was shed at the two-celled stage. Pollination drops were exuded from only a few ovules at one time. Pollen contacting the pollination drop was rapidly taken in. The pollination drop was withdrawn into the micropyle which was later sealed by enlargement of cells lining the micropylar canal. Megasporogenesis occurred in late February but female gametophytes did not mature and fertilization did not occur until late May. An archegonial complex formed containing seven to nine archegonia, of which several usually were fertilized. Proembryo development varied depending upon the size and shape of the archegonia. Usually, a 12-celled, three-tiered proembryo formed by mid-June. Cleavage polyembryony was not observed. Embryos were mature by mid-August and most seed was shed in September and October.The potential seed set was only 16 seeds per cone and filled seed averaged only 2.6 per cone. Most potential seed was lost because of early ovule abortion from unknown causes, insect damage, or low temperatures at or shortly after pollination. Some potential seeds were lost because the ovules were not pollinated or the embryos aborted. These seeds were soft but nearly normal appearing and contained spongy female gametophyte tissue. Methods of maximizing seed production are suggested.

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.

scholarly journals ABAP1 Plays a Role in the Differentiation of Male and Female Gametes in Arabidopsis thaliana

2021 ◽  
Vol 12 ◽  
Author(s):  
Luiz M. Cabral ◽  
Hana P. Masuda ◽  
Helkin F. Ballesteros ◽  
Janice de Almeida-Engler ◽  
Márcio Alves-Ferreira ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
Female Gametophyte ◽  
Target Genes ◽  
Asymmetric Cell Division ◽  
Male Gametophyte ◽  
Leaf Growth ◽  
Plant Reproduction ◽  
Vegetative Development ◽  
Male And Female ◽  
Cell Divisions

The correct development of a diploid sporophyte body and a haploid gametophyte relies on a strict coordination between cell divisions in space and time. During plant reproduction, these divisions have to be temporally and spatially coordinated with cell differentiation processes, to ensure a successful fertilization. Armadillo BTB Arabidopsis protein 1 (ABAP1) is a plant exclusive protein that has been previously reported to control proliferative cell divisions during leaf growth in Arabidopsis. Here, we show that ABAP1 binds to different transcription factors that regulate male and female gametophyte differentiation, repressing their target genes expression. During male gametogenesis, the ABAP1-TCP16 complex represses CDT1b transcription, and consequently regulates microspore first asymmetric mitosis. In the female gametogenesis, the ABAP1-ADAP complex represses EDA24-like transcription, regulating polar nuclei fusion to form the central cell. Therefore, besides its function during vegetative development, this work shows that ABAP1 is also involved in differentiation processes during plant reproduction, by having a dual role in regulating both the first asymmetric cell division of male gametophyte and the cell differentiation (or cell fusion) of female gametophyte.

Sexual reproduction of Engelmann spruce (Picea engelmannii)

1981 ◽  
Vol 59 (5) ◽  
pp. 793-810 ◽  
Author(s):  
Hardev Singh ◽  
John N. Owens
Keyword(s):  
Sexual Reproduction ◽  
Female Gametophyte ◽  
Developmental Stages ◽  
Young Female ◽  
Picea Engelmannii ◽  
Spongy Tissue ◽  
Cell Stage ◽  
Engelmann Spruce ◽  
Lower Elevation ◽  
Mother Cells

The anatomy and phenology of sexual reproduction of Picea engelmannii Parry from three sites near Prince George, B.C., has been described. The developmental stages at the higher elevation and consequently colder site lagged by 1–2 weeks compared with the lower elevation sites. Pollen mother cells underwent meiosis in mid-May and the five-celled pollen was shed from the end of June to the 1st week of July. The ovules went through the winter rest in the megaspore mother cell stage. The latter underwent meiosis in mid-May to form linear tetrads. The integument was initiated in the postdormancy stages and developed two micropylar prongs which seem characteristic of the genus. The nucellus showed a massive nucellar cap and a pollen chamber formed by the degeneration of cells. The young female gametophyte was surrounded by a spongy tissue which persisted at the chalazal end where the megaspore wall was thickest. The female gametophyte usually bore two archegonia which were fertilised in mid-July (3 weeks after pollination). The embryo developed over the next 3 months. Two main factors which contribute to ovule abortion are failure of pollination and degeneration of embryo during early development.

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 Rape embryogenesis. IV. Appearance and disappearance of starch during embryo development

2014 ◽  
Vol 51 (3-4) ◽  
pp. 381-387 ◽  
Author(s):  
Teresa Tykarska
Keyword(s):  
Apical Part ◽  
Embryo Axis ◽  
Starch Grains ◽  
Cell Divisions ◽  
Embryo Cells ◽  
Dividing Cells ◽  
Gradual Accumulation ◽  
Black Seeds ◽  
Mother Cells ◽  
Storage Starch

Starch appears first in the suspensor of the proembryo with two-cell apical part. It is observed in the embryo proper from the octant stage. At first it is visible in all the embryo cells in the form of minute transient grains which disappear during cell divisions. But the columella mother cells and their derivatives have persistent large grains. When the embryo turns green in the heart stage a gradual accumulation of storage starch begins and lasts to the end of embryogenesis. Storage starch grains appear first in the auter cortex layers of the hypocotyl where the largest grains are to be found later, and afterwards in all the other tissues. Starch is usually absent in the frequently dividing cells, but even there it appears in the form of minute grains after the end of cell divisions. Disappearance of starch starts when the intensive green colour of the seed coat begins to fade. The first to disappear are the smallest granules in the regions where they were noted latest. In the embryo axis the starch grains remain deposited longest in dermatogen and cortex cells in the lower hypocotyl part. They are visible there, still when the seed turns brown. In black seeds starch may be only found in the columella the cells of which throughout embryogenesis contain amyloplasts filled with starch. These grains disappear completely at the time when the seeds become dry.

scholarly journals Meiotic Chromosome Behavior and Capsule Setting in Doritaenopsis Hybrids

2008 ◽  
Vol 133 (1) ◽  
pp. 107-116 ◽  
Author(s):  
Pablo Bolaños-Villegas ◽  
Shih-Wen Chin ◽  
Fure-Chyi Chen
Keyword(s):  
Cell Division ◽  
Pollen Mother Cell ◽  
Chromosome Pairing ◽  
Chromosomal Aberrations ◽  
High Frequency ◽  
Mother Cell ◽  
Seed Set ◽  
Pollen Viability ◽  
High Pollen ◽  
Mother Cells

The development of new cultivars in Doritaenopsis Guillaum. & Lami orchids is often hindered by factors such as low seed count in hybrids. Cytological study may offer the ability to develop new hybrids by revealing cultivars with good chromosome pairing and high pollen viability, which are somewhat difficult to obtain under current breeding programs. Cross pollination, pollen viability, and chromosomal behavior during meiosis were analyzed to reveal the relation between seed fertility and capsule set in Doritaenopsis hybrids. The number of mature capsules harvested and their relative seed content were used as indices of crossing availability. The results of meiosis were evaluated according to pollen viability detected by fluorescein diacetate and quantification of sporad types by acid fuchsin staining. Chromosome number and pairing at meiosis were observed in root tips or in samples of pollen mother cells. A positive relation was found among high seed set, high frequency of viable tetrads, high degree of chromosome pairing, and low frequency of chromosomal aberrations such as inversions and translocations. On the basis of these factors, three types of hybrids could be distinguished. In type one hybrids, chromosomes paired as bivalents, pollen mother cells divided into tetrads, and capsule setting occurred after pollination of pollen acceptors. In type two hybrids, chromosomes remained mainly as univalents that developed into micromeiocytes, pollen mother cell division was disrupted, and seed recovery was low after pollination. Type three hybrids showed chromosomes paired mostly as multivalents, chromosome bridges, pollen mother cell division with massive failure, and little fertility. In Doritaenopsis orchids, high pollen viability and high fertility depends on a high frequency of normal tetrads, and low seed set in cross-pollination is predicted with micronuclei in the end products of meiosis. The occurrence of chromosomal aberrations may suggest a process of genome differentiation that could compromise breeding efforts if not taken into consideration.

scholarly journals Identification and evaluation of the novel genes for transcript normalization during female gametophyte development in sugarcane

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e12298
Author(s):  
Maokai Yan ◽  
Xingyue Jin ◽  
Yanhui Liu ◽  
Huihuang Chen ◽  
Tao Ye ◽  
...  
Keyword(s):  
Gene Expression ◽  
Sexual Reproduction ◽  
Reference Genes ◽  
Female Gametophyte ◽  
Developmental Stages ◽  
Reproductive Organs ◽  
The Novel ◽  
Biofuel Feedstock ◽  
Gametophyte Development ◽  
Female Gametophyte Development

Background Sugarcane (Saccharum spontaneum L.), the major sugar and biofuel feedstock crop, is cultivated mainly by vegetative propagation worldwide due to the infertility of female reproductive organs resulting in the reduction of quality and output of sugar. Deciphering the gene expression profile during ovule development will improve our understanding of the complications underlying sexual reproduction in sugarcane. Optimal reference genes are essential for elucidating the expression pattern of a given gene by quantitative real-time PCR (qRT-PCR). Method In this study, based on transcriptome data obtained from sugarcane ovule, eighteen candidate reference genes were identified, cloned, and their expression levels were evaluated across five developmental stages ovule (AC, MMC, Meiosis, Mitosis, and Mature). Results Our results indicated that FAB2 and MOR1 were the most stably expressed genes during sugarcane female gametophyte development. Moreover, two genes, cell cycle-related genes REC8 and CDK, were selected, and their feasibility was validated. This study provides important insights into the female gametophyte development of sugarcane and reports novel reference genes for gene expression research on sugarcane sexual reproduction.

scholarly journals Studies on genome size estimation, chromosome number, gametophyte development and plant morphology of salt-tolerant halophyte Suaeda salsa

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Yan Cheng ◽  
Pan Yang ◽  
Lihua Zhao ◽  
S. V. G. N. Priyadarshani ◽  
Qiao Zhou ◽  
...  
Keyword(s):  
Genome Size ◽  
Female Gametophyte ◽  
Plant Morphology ◽  
High Salt ◽  
Suaeda Salsa ◽  
Alkali Resistance ◽  
Future Research ◽  
Size Estimation ◽  
Salt Tolerant ◽  
Male And Female

Abstract Background Soil salinization and alkalization are among the major agricultural threats that affect crop productivity worldwide, which are increasing day by day with an alarming rate. In recent years, several halophytes have been investigated for their utilization in soil remediation and to decipher the mechanism of salt-tolerance in these high salt tolerant genetic repositories. Suaeda salsa is an annual halophytic herb in the family Amaranthaceae, displaying high salt and alkali-resistance and having nutritive value. However, the fundamental biological characteristics of this valuable plant remain to be elucidated until today. Results In this study, we observed the morphology and development of Suaeda salsa, including seed morphology, seed germination, plant morphology, and flower development. Using microscopy, we observed the male and female gametophyte developments of Suaeda salsa. Also, chromosome behaviour during the meiosis of male gametophyte was studied. Eventually, the genome size of Suaeda salsa was estimated through flow cytometry using Arabidopsis as reference. Conclusions Our findings suggest that the male and female gametophyte developments of Suaeda salsa are similar to those of the model plant Arabidopsis, and the diploid Suaeda salsa contains nine pairs of chromosomes. The findings also indicate that the haploid genome of Suaeda salsa is approximately 437.5 MB. The observations and results discussed in this study will provide an insight into future research on Suaeda salsa.

scholarly journals Epigenetic Regulation of Plant Gametophyte Development

2019 ◽  
Vol 20 (12) ◽  
pp. 3051 ◽  
Author(s):  
Vasily V. Ashapkin ◽  
Lyudmila I. Kutueva ◽  
Nadezhda I. Aleksandrushkina ◽  
Boris F. Vanyushin
Keyword(s):  
Mother Cell ◽  
Female Gametophyte ◽  
Male Gametophyte ◽  
Endosperm Development ◽  
Epigenetic Changes ◽  
Gametophyte Development ◽  
Daughter Cells ◽  
Second Stage ◽  
Somatic Tissues ◽  
Mother Cells

Unlike in animals, the reproductive lineage cells in plants differentiate from within somatic tissues late in development to produce a specific haploid generation of the life cycle—male and female gametophytes. In flowering plants, the male gametophyte develops within the anthers and the female gametophyte—within the ovule. Both gametophytes consist of only a few cells. There are two major stages of gametophyte development—meiotic and post-meiotic. In the first stage, sporocyte mother cells differentiate within the anther (pollen mother cell) and the ovule (megaspore mother cell). These sporocyte mother cells undergo two meiotic divisions to produce four haploid daughter cells—male spores (microspores) and female spores (megaspores). In the second stage, the haploid spore cells undergo few asymmetric haploid mitotic divisions to produce the 3-cell male or 7-cell female gametophyte. Both stages of gametophyte development involve extensive epigenetic reprogramming, including siRNA dependent changes in DNA methylation and chromatin restructuring. This intricate mosaic of epigenetic changes determines, to a great extent, embryo and endosperm development in the future sporophyte generation.

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