Wall layers of anther have different functions most importantly they help in providing nutrition to developing pollens and also help in anther dehiscence.
Plant fertilization is the union of male and female gametes (reproductive cells) to produce a zygote (fertilized egg)
Double Fertilization
Both the male gametes/sperms participate in sexual reproduction.
Two male gametes fuse with one female gamete wherein one male gamete fertilizes the egg to form a zygote, whereas the other fuses with two polar nuclei to form an endosperm
Triple fusion is the fusion of the male gamete with two polar nuclei inside the embryo sac of the angiosperm.
Porogamy - entry through the micropyle.
Chalazogamy - entry through the Chalaza
Mesogamy - entry through the middle part or the integuments
Steps leading to fertilization
Germination of the pollen grain:
Stigma function is to provide place of lodging and germination of the pollen grain after pollination.
Types of stigmas-
Wet stigmas
Secrete exudates like water and other nutrients
In the form of droplets on the stigma.
Exudates made up of a mix of water, lipids, sugars, amino acids, phenolic compounds.
Highly viscous and adhesive. Ex: Petunia, Zea etc.
Dry stigma
Do not secrete exudates Ex: Gossypium
Double Fertilization & Triple Fusion:
Both the male gametes are involved in the fertilization.
Fertilize two different components of the embryo sac - Double Fertilization
One fuses with the egg nucleus (syngamy) -> Zygote(2n)
second fuses with polar nuclei -> primary endosperm nucleus (PEN).
Involves fusion of three nuclei - Triple fusion -> Endosperm(3n)
Pollen tube in the synergids:
Entry only through micropyle. Guided by oburator
Presence of chemotropic substances
Collapse of one the synergids prior to entry of the pollen tube.
Pollen tube in the synergids:
Entry only through micropyle. Guided by oburator
Presence of chemotropic substances
Collapse of one the synergids prior to entry of the pollen tube.
Discharge of pollen tube contents (two male gametes, vegetative nucleus and cytoplasm) into the synergids.
Disorganization of tube nucleus
Polyspermy &Heterofertilization
Heterofertilization - Type of double fertilization in plants in which endosperm and embryo are genetically different.
This happens when two different sperm nuclei from two different pollen tubes happen to enter the same embryo sac.
Dr. T. Annie Sheron
Annie Sheron
Kakatiya Government College
Wall layers of anther have different functions most importantly they help in providing nutrition to developing pollens and also help in anther dehiscence.
Plant fertilization is the union of male and female gametes (reproductive cells) to produce a zygote (fertilized egg)
Double Fertilization
Both the male gametes/sperms participate in sexual reproduction.
Two male gametes fuse with one female gamete wherein one male gamete fertilizes the egg to form a zygote, whereas the other fuses with two polar nuclei to form an endosperm
Triple fusion is the fusion of the male gamete with two polar nuclei inside the embryo sac of the angiosperm.
Porogamy - entry through the micropyle.
Chalazogamy - entry through the Chalaza
Mesogamy - entry through the middle part or the integuments
Steps leading to fertilization
Germination of the pollen grain:
Stigma function is to provide place of lodging and germination of the pollen grain after pollination.
Types of stigmas-
Wet stigmas
Secrete exudates like water and other nutrients
In the form of droplets on the stigma.
Exudates made up of a mix of water, lipids, sugars, amino acids, phenolic compounds.
Highly viscous and adhesive. Ex: Petunia, Zea etc.
Dry stigma
Do not secrete exudates Ex: Gossypium
Double Fertilization & Triple Fusion:
Both the male gametes are involved in the fertilization.
Fertilize two different components of the embryo sac - Double Fertilization
One fuses with the egg nucleus (syngamy) -> Zygote(2n)
second fuses with polar nuclei -> primary endosperm nucleus (PEN).
Involves fusion of three nuclei - Triple fusion -> Endosperm(3n)
Pollen tube in the synergids:
Entry only through micropyle. Guided by oburator
Presence of chemotropic substances
Collapse of one the synergids prior to entry of the pollen tube.
Pollen tube in the synergids:
Entry only through micropyle. Guided by oburator
Presence of chemotropic substances
Collapse of one the synergids prior to entry of the pollen tube.
Discharge of pollen tube contents (two male gametes, vegetative nucleus and cytoplasm) into the synergids.
Disorganization of tube nucleus
Polyspermy &Heterofertilization
Heterofertilization - Type of double fertilization in plants in which endosperm and embryo are genetically different.
This happens when two different sperm nuclei from two different pollen tubes happen to enter the same embryo sac.
Dr. T. Annie Sheron
Annie Sheron
Kakatiya Government College
The Shoot apex is also known as the terminal bud of plants that grows from 0.1-1.0 mm and consists of the apical meristem, developing leaves and the immediate surrounding leaf primordial. The shoot apex is present in both dicot and monocot plants.
Vascular Cambium & Seasonal activity & its Role in Stem & RootFatima Ramay
Vascular Cambium & Seasonal activity & its Role in Stem & Root:
The vascular cambium (pl. cambia or cambiums) is a lateral meristem in the vascular tissue of plants.
The vascular cambium is a cylindrical layer of cambium that runs through the stem of a plant that undergoes secondary growth.
In Dicots:
The vascular cambium is in dicot stems and roots, located between the xylem and the phloem in the stem and root of a vascular plant, and is the source of both the secondary xylem growth (inwards, towards the pith) and the secondary phloem growth (outwards).
In Monocots:
Monocot stems, such as corn, palms and bamboos, do not have a vascular cambium and do not exhibit secondary growth by the production of concentric annual rings. They cannot increase in girth by adding lateral layers of cells as in conifers and woody dicots.
Cambium of some plants remains active for the entire period of their life, i.e., cambial cells divide and resulting cells mature to form xylem and phloem elements.
This type of seasonal activity usually found in the plants present in the tropical regions, and not all plants show cambial activity.
Percentage of ringless trees in the rain forests of;India : 75%Amazon : 43%Malaysia : 15%
In regions with definite seasonal climate; seasonal activity of cambium ceased with onset of unfavorable conditions; In Autumn, it enters the dormant state and lasts for the end of summer; In Spring, cambium again becomes active.
Duration of cambial activity is also affected by day-length, e.g., In Robinia pseudoacacia, cambium is dormant under short-day condition.
The cambium cells formed in circular in cross section from the beginning onwards.
The cambial ring is partially primary (fascicular cambium) and partially secondary (interfascicular cambium).
Periderm originates from the cortical cells (extra stelar in origin).
In Dicot stem, for mechanical support xylem is with comparatively smaller vessels, greater fibers and less parenchyma.
More amount of cork is produces for protection.
Lenticels on periderm are very prominent.
The cambial ring formed is wavy in the beginning and later becomes circular.
The cambium ring is completely secondary in origin.
Periderm originates from the pericycle (intra stelar in origin).
In Dicot root, xylem is with big thin walled vessels with few fibers and more parenchyma.
Less amount of cork is produced as root is underground.
Lenticels on periderm are not very prominent.
Double fertilization is the process found in angiosperms in which out of the two male gametes released inside the embryo sac, one fuses with the egg cell (syngamy) and another fuse with secondary nucleus (triple fusion).
Megasporogenesis is the process of formation of megaspores from the megaspore mother cell.
In the hypodermal region of nucellus towards the micropylar end develops a primary archesporial cell.
Dr. T. Annie Sheron
Annie Sheron
Kakatiya Government College
This slide serves as the completing part of BIO 101. It covers topics such as Basic reproduction, Genetics and heredity, ecology, evolution, animals and plants; lower and higher.
The Shoot apex is also known as the terminal bud of plants that grows from 0.1-1.0 mm and consists of the apical meristem, developing leaves and the immediate surrounding leaf primordial. The shoot apex is present in both dicot and monocot plants.
Vascular Cambium & Seasonal activity & its Role in Stem & RootFatima Ramay
Vascular Cambium & Seasonal activity & its Role in Stem & Root:
The vascular cambium (pl. cambia or cambiums) is a lateral meristem in the vascular tissue of plants.
The vascular cambium is a cylindrical layer of cambium that runs through the stem of a plant that undergoes secondary growth.
In Dicots:
The vascular cambium is in dicot stems and roots, located between the xylem and the phloem in the stem and root of a vascular plant, and is the source of both the secondary xylem growth (inwards, towards the pith) and the secondary phloem growth (outwards).
In Monocots:
Monocot stems, such as corn, palms and bamboos, do not have a vascular cambium and do not exhibit secondary growth by the production of concentric annual rings. They cannot increase in girth by adding lateral layers of cells as in conifers and woody dicots.
Cambium of some plants remains active for the entire period of their life, i.e., cambial cells divide and resulting cells mature to form xylem and phloem elements.
This type of seasonal activity usually found in the plants present in the tropical regions, and not all plants show cambial activity.
Percentage of ringless trees in the rain forests of;India : 75%Amazon : 43%Malaysia : 15%
In regions with definite seasonal climate; seasonal activity of cambium ceased with onset of unfavorable conditions; In Autumn, it enters the dormant state and lasts for the end of summer; In Spring, cambium again becomes active.
Duration of cambial activity is also affected by day-length, e.g., In Robinia pseudoacacia, cambium is dormant under short-day condition.
The cambium cells formed in circular in cross section from the beginning onwards.
The cambial ring is partially primary (fascicular cambium) and partially secondary (interfascicular cambium).
Periderm originates from the cortical cells (extra stelar in origin).
In Dicot stem, for mechanical support xylem is with comparatively smaller vessels, greater fibers and less parenchyma.
More amount of cork is produces for protection.
Lenticels on periderm are very prominent.
The cambial ring formed is wavy in the beginning and later becomes circular.
The cambium ring is completely secondary in origin.
Periderm originates from the pericycle (intra stelar in origin).
In Dicot root, xylem is with big thin walled vessels with few fibers and more parenchyma.
Less amount of cork is produced as root is underground.
Lenticels on periderm are not very prominent.
Double fertilization is the process found in angiosperms in which out of the two male gametes released inside the embryo sac, one fuses with the egg cell (syngamy) and another fuse with secondary nucleus (triple fusion).
Megasporogenesis is the process of formation of megaspores from the megaspore mother cell.
In the hypodermal region of nucellus towards the micropylar end develops a primary archesporial cell.
Dr. T. Annie Sheron
Annie Sheron
Kakatiya Government College
This slide serves as the completing part of BIO 101. It covers topics such as Basic reproduction, Genetics and heredity, ecology, evolution, animals and plants; lower and higher.
Plant embryology and palynology, history of plant embryology, General basic terms in embryology (sporogenesis, Gametogenesis, Pollination, Fertilization, Double fertilization, Endosperm, Embryogenesis), Diagnostic embryological characters, Primitive and advance embryological characters, Role of embryology and palynology in taxonomy.
This presentation contains a lots of information about the contribution of the scientists who works in the field of reproductive biology of angiosperms.
This ppterrestrial habitt explains about the archegoniate plants, their adaptations, development of different support systems in transition from aquatic to terrestrial habit, about their alternation of generations, etc.
A dam can also be used to collect or store water which can be evenly distributed between locations. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees (also known as dikes) are used to manage or prevent water flow into specific land regions. The earliest known dam is the Jawa Dam in Jordan, dating to 3,000 BC
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
This presentation intends to explore the communication of the cell within and others for sustainability along the regulation mechanisms by the cellular neural networks and others to sing the song of the life.
Bioenergetics is an important domain in biology. This presentation has explored ATP production and its optimum utilization in biological systems along with certain theories and experiments to give a bird's eye view of this important issue.
This presentation offers the bird's eye view of the cell as the basic structural and functional unit of life. It also addresses the origin of eukaryotic cells from the prokaryotic cell by the endosymbiotic theory.
This presentation has been intended to offer a bird's eye view about the phylogenetic classification of the plant kingdom in general and the Engler and Prantl system in particular with merits and demerits.
This PPT has been made to explore the plant classification in general and the classification as made by Bentham & Hooker for the classification of the flowering plants. It also offers the history of plant classification along with the merits and demerits of this aforesaid classification.
Energy and the biological systems are joined together and no biological world is almost impossible without ATP. This study material intends to explore the beauty of ATP to drive different biological processes.
This PPT offers a bird's eye view of ICBN and its different rules along with regulations for the naming of plants. It also highlights the history of IBC and its contribution to plant taxonomy.
This presentation intends to offer the basic features of plant metabolism along with the different types of mechanisms to regulate and control the metabolic pathways.
This presentation has been designed to give the foundation of taxonomy in general and Plant Taxonomy in particular as a matter of pleasure to explore the diversity of the plant world.
Sex and sexuality are very common words in biology but para-sexuality is a little bit uncommon, several organisms in general and fungi in particular have the pleasure of sexuality to bring variations by beside sex. This PPT explores the beauty of para-sexuality for the academic fraternity.
Sex life in fungi is not less fascinating than in other organisms. Heterosexuality is a matter of pleasure to explore the diversity of sex in fungi along with its cause and consequences. You can find a pleasure to go through the content.
This PowerPoint wants to explore the bird's eye view of the reproduction of bacteria in general and the genetic recombination of bacteria in particular.
This presentation gives the bird's eye view of bacterial nutrition along with some other issues required to understand bacterial diversity as far as nutrition is concerned.
This presentation explores the food value of mushrooms along with the long-term and short-term storage procedures. It also offers a detailed account of the nutrients that remain present in the edible mushrooms.
If you want to explore the role of Cyanobacteria in soil fertility in general & Azolla-Anabena association in particular, you can visit this PowerPoint Presentation.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
2. Reproductive Biology is the branch of sciences deals with the different
aspects of the reproductive issues of organisms in general and sexual
reproduction in particular in the light of morphological, cytological &
embryological attributes. Sexual reproduction involves a series of changes
like preparation of sex organs(Gonads), formation of haploid gametes,
union of gametes as fertilization, post zygotic changes and post embryonic
changes making passage to give offspring with variation. In plants, it is
mediated by alternation of generations via microsporogenesis,
megasporogenesis, pollination, fertilization and development of mature
embryo. This fundamental process of reproduction is DNA replication. In
other words, if an organism wants to continue its species, then they need to
transfer their traits to the next generation by DNA (genetic information)
copying which occurs during the process of reproduction. We know
asexually reproducing organisms copy their DNA and divide themselves
into new cells which are their clones.
3. Since the process of replication is not completely reliable, there are
chances of variation, but they are quite limited. Organisms need to adapt
themselves to the changing environment; the creation of variants needs to
be hastened for this reason. This will only happen when there is a union of
two different DNAs. This highlights the significance of sexual
reproduction in organisms. If two reproducing cells simply join, the
chromosome number in the new organism will be doubled. But this cannot
happen because the number of chromosomes in each cell of every organism
is fixed – the same holds good for the reproducing cell. Thus, the
reproducing cells from both parents reduce their chromosome number into
the half before fusion and are called gametes (germ cells). In simple
organisms, the size and shape of gametes are almost the same. But in
higher organisms, a male gamete is small and mobile while female gamete
is large, immobile and they store food for the fetus. The gametes are
produced in a specialized system called the reproductive system.
4.
5. The following basic steps are involved----
The transformation of the vegetative phase into reproductive phase by the
induction of flower through a series of changes leading to the development
of flower,
Microsporogenesis in stamen to form haploid poille4n grains-the 1st cell of
the male gametophyte and the megasporogenesis to form the megaspore as
the 1st cell of the female gametophyte,
Pollination: Either by self pollination( autogamy or Geitonogamy) or cross
pollination, Pollen reaches the stigma of a flower.
Germination: Pollen germinates and forms a pollen tube that reaches the
ovary, and the haploid male gamete is released into the embryo sac by
different embryological processes.
The ovule by this time get ready for the development of embryo sac
comprising of egg, secondary apparatus & others
Fusion: Male gamete fuses with female gamete and forms zygote.
Post-zygotic changes lead to the formation of embryo, seed formation takes
place, baby plants derived---alternation of generation comes to an end.
6.
7. As we enter the 21st year of the journal Sexual Plant Reproduction, it seems
both fitting and appropriate to consider the genesis both of this journal and its
parent organization, the International Association for Sexual Plant
Reproduction Research (IASPRR)—particularly through its much longer
history of plant sexual reproduction congresses, informal interactions and this
area of scientific pursuit as it is transformed in the modern era. The science of
sexual plant reproduction has a long history that reaches beyond the 315 years
interval since Camerarius uncovered the sexuality of plants (Žárský and Tupý
1995), passing 150 years of neglect before the discovery of gametes, and then a
great period of exploration in the 1800s concluding with the discovery of
double fertilization in 1898 by Nawashin.From Theophrastus,
Herodotus,Leewenhoek, Grew, Camerrius,Kolreuter different plant scientists
have enriched this domain. Giovanni Battita Amici(1824) made significant
contribution by discovering the pollen tube while studying the stigma of
Portulaca oleracea.He splitted open the pollen tube and entered the tissue of
stigma.
8. The formation of embryo in plants as the onset of life was a very crucial
question and the dilemma was about the origin of the embryo. William
Hofmeister first demonstrated that in every case, the embryo originated
from pre-existing cell in the embryo sac and not from the pollen tube on
the basis of the observations of 38 species belonging to 19 genera of
angiosperms. This observations ended a rigid controversy between
Schliden and his opponents. The experimental research along with its
proper documentation of the origin of embryo and its nature of origin
become crystal clear to the biologists after this epoch making research and
this made a new avenue of the understanding about the sexual reproduction
of the higher plants. Hofmeister is widely credited with discovery of
alternation of generations as a general principle in plant life. His proposal
that alternation between a spore-bearing generation (sporophyte) and a
gamete-bearing generation (gametophyte) constituted a unifying theory of
plant evolution that was published in 1851.
9. Eduard Strasburger, director of the Botany Institute and the Botanical
Garden at the University of Bonn from 1881 to 1912, was one of the most
admirable scientists in the field of plant biology, not just as the founder of
modern plant cell biology but in addition as an excellent teacher who
strongly believed in "education through science." He contributed to plant
cell biology by discovering the discrete stages of karyokinesis and
cytokinesis in algae and higher plants, describing cytoplasmic streaming in
different systems, and reporting on the growth of the pollen tube into the
embryo sac and guidance of the tube by synergides. Strasburger raised
many problems which are hot spots in recent plant cell biology, e.g.,
structure and function of the Plasmodesmata in relation to phloem loading
(Strasburger cells) and signaling, mechanisms of cell plate formation,
vesicle trafficking as a basis for most important developmental processes,
and signaling related to fertilization. Demonstrated the wide spread
occurrence of the binucleate condition of pollen grains and worked out the
organisation of the embryo sac of Polygonum divaricutum.
10. He Also pointed out that the nucellus lying close to the apex of the embryo
sac become richly protoplasmic and divide to form small groups of cells
which project into the cavity of the embryo sac and grow into embryo on
the basis of the ontogeny study of citrus aurantium.
Discovered syngamy, development of embryo sac from megaspore mother
cells and pointed out modification of synergids in the process of
fertilisation.
Strasburger was the author of the important book Ueber Zellbildung und
Zelltheilung (1875), and an influential Lehrbuch der Botanik fuer
Hochschulen (1894, 196729; Textbook of Botany, 1898, 19657). Under his
direction, the botanical institute became a world center for research in
botany and especially in the newly emerging science of cell biology.
Strasburger's early research dealt with the embryology of liverworts, ferns,
and conifers. He recognized the homology of the archegonia of the fern
with the embryo sac of conifers.
11. Double fertilization is a characteristic feature of angiosperms. Syngamy
causes the formation of embryo, where the male and female gametes fuse.
Along with that the secondary polar nuclei fuse with male gamete to form
triploid endosperm. It provides the function of nourishment.
Navashin's embryological research led him to the important discovery in
1898 of double fertilization in angiosperms. Observing fertilization in the
Turk's- cap lily (Lilium martagon) and Fritillaria tenella, he was the first to
note that this process involves not one but two sperm, which form in the
pollen tube. In a study of Lilium martagon and Frititlaria tenella. showed
that in angiosperm both male gamete are concerned in fertilization, on
fusing with the egg (syngamy) and the other with the two polar nuclei
(triple fusion).In the study of Lilium sp, he observed that male gamete on
fusing with egg as syngamy and other male gamete with two polar nuclei
as triple fusion. Double fertilization as universal occurrence of
angiosperms. Explored a new breeze in the developmental biology of
angiosperms.
12. Panchanan Maheswari was an eminent Indian botanist and he was known for
his discovery in the technique of test-tube fertilization of angiosperms.
- Test tube fertilization or in vitro fertilization is a type of process involving
fertilization where the egg is fused with the sperm outside i.e. in a glass or test
tube. The whole process is monitored as the fertilized egg is developed into an
embryo. Cultivation of plant tissue and other organs on an artificial media in a
test tube is in vitro technique. P. Maheshwari who served as Professor and
Head of the Department of Botany, University of Delhi from 1950 to 1966
built a flourishing school of embryology which became internationally
recognized. His colleagues and students have contributed significantly to all
areas of embryology through integrative approaches. In memory of his birth
centenary year, we have prepared this article that summarizes the work done by
his students and traces the phenomenal advances made in some areas in the
post-Maheshwari era. Father of Indian Embryology, famous for test tube
fertilization of angiosperms by tissue culture methods. Wrote an important
book on “Embryology of Angiosperms” along with a number of contributions
in applied and Experimental plant embryology. The valuable contributions are
available with the genera like Paeonia,Trapa, Butomus,Peganum,Parasssia etc
& families like Crassulaceae, Liliaceae,Loranthaceae,Lemnaceae,Cyperaceae
etc.
13. During the 20th century, significant advances have been made in
developmental and comparative embryology and its role in taxonomic
considerations.Howerver, the causes of the variations in spindle
organization during microsporogenesis, pollen structure in Cyperaceae and
Epacridaceae, pollen bud development in some members of Rubiaceae,
pollen embryo sac in experimental embryology are some of the works .
◦ W.A.Jensen
Orchid is the most important epiphytes and it is worthy to be praised by the
beauty lovers due to its showy & bizarrely shaped structure.It belongs to
the most developed family, Orchidaceae and it encompasses 6-11% of the
seed plants. Starts in the Orchid embryology. He also contributed a lot in
Capsella embryogenesis, the central cell plays an important role in the
double fertilisation.The relationship to the central cell to the other cells of
the mature megagemetophyte and its possible role in embryogenesis was
discussed by W.A .Jensen in the paper entitled”Capsella Embryogenesis:
The central cell”.
14. Heslop Harrison was an eminent English professor of botany who was
based in Newcastle in the middle years of the twentieth century and who
sired a mini-dynasty of other eminent biologists. He was a Fellow of the
Royal Society as was one of his sons; a very unusual occurrence.
Genetically work on plants on wild roses & Willows, Rose hybrid & Salix
hybrid, Light effect on the pupae of Butterfly.
A number of Indian scientists like Swamy, Maheswari, johri,Vasil, shivana
& others have contributed a lot to enrich this subject.
If you have the passion, you can a do a lot by your research & innovative
mind.
15.
16. 1. Google for images,
2. Different websites to exp0lore the idea,
3. An Introduction to embryology- P. Maheswari
4.Plant anatomy 7 embryology- Pandey & Chakdah
5.A textbook of Botany- B.P. Pandey
6.The embryology of angiosperms- S.S. Bhojwani,
7. The Embryology of angiosperms- Bhojwani, Bhatnagar & Dantu
Disclaimer: This presentation has been made to enrich open source of
knowledge without any financial pleasure.