This document provides information on the structure and development of stamens and pollen grains, ovules and embryo sacs, and the process of fertilization in angiosperms.
[1] It describes the basic anatomy of a stamen including the filament, anther, and microsporangia. Meiosis in the microsporangia produces microspores that develop into pollen grains.
[2] The structure of an ovule including the integuments, nucellus, embryo sac, and its development via megasporogenesis is explained.
[3] The process of double fertilization is summarized where one sperm cell fuses with the egg to form
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).
description of different types of reproductive organs, developmental stages and process of reproduction in Cycas. Various internet sources have been used.
This is a detailed presentation on Morphology, anatomy and reproduction of Marchantia spp. with high quality pics and eye capturing transitions and animations
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).
description of different types of reproductive organs, developmental stages and process of reproduction in Cycas. Various internet sources have been used.
This is a detailed presentation on Morphology, anatomy and reproduction of Marchantia spp. with high quality pics and eye capturing transitions and animations
The "Telome theory" of Walter Zimmermann (1930, 1952) is the most accepted theory that is based on fossil record and synthesizes the major steps in the evolution of vascular plants.
It describes how the primitive type of vascular plants developed from Rhynia like plants.
Wall layers of anther have different functions most importantly they help in providing nutrition to developing pollens and also help in anther dehiscence.
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.
1. INTRODUCTION
A gametophyte is a stage in the life cycle of plants and algae that undergo alternation of generations.
The gametophyte is the sexual phase in the life cycle of plants and algae.
Cell division of the zygote results in a new diploid multicellular organism, the second stage in the life cycle known as the sporophyte, the function of which is to produce haploid spores by meiosis.
2. Structure of Female Gametophyte
The female gametophyte is also called the embryo sac.
In angiosperms it mostly develops as a seven celled, eight-nucleate structure.
It consists of three antipodal cells, one central cell, two synergid cells, and one egg cell mostly.
3.Structure of Female Gametophyte
It generally contain antipodal cells at chalazal ends, an egg cell and two synergids at microplyar ends, and a center containing two polar nuclei.
Embryo sec is expect the center binucleate cell.
The process of formation of embryo sac is known as megasporogenesis.
4.The female gametophyte first arise as a tiny protuberance from the placenta, in the cavity of the overy.
As it mature,the ovule consists of a nutritive cellular mass known as nucellus, protected by two integuments, and attached to the placenta by a funiculus.
Even at an early stage, one cell becomes evident in the nucellus, which is known as the megaspore mother cell(MMC).
5.MMC is diploid (2n)
The MMC then increases in size, and divides twice (meiotically) to from 4 megaspore as ‘linear tetrad’
The first division is a reduction division
The resultant megaspores are haploid (n)
Out of the four megaspores, three degenerate, forming caps, while one remains functional.
6.This functionl megaspore is haploid (n)
The functional megaspore, then grows rapidally, by absorbing nutrition from nucellus, and forms the embryo sac.
The process of formation of embryo sac is known as megasporogenesis.
The embryo sac consists of one nucleus.
The nucleus divided into two daughter nuclei, which move towards the poles.
The pole of the embryo sac, closer to the chalaza, is the chalazal end,and the one closer to the microphyle is the micropylar end.
7.Each daughter nuclei divides again, and result in four nuclei.
Each nuclei divides again, for the last time, and result in eight nuclei.
One nuclei from each end, come to the centre, and fuse to from a diploid secondary nucleus.
The nuclei at the chalazal end, get surronded by cytoplasm, and form three distinct, haploid, antipodal cells.
Similarly, the nuclei at the micropylar end, form the egg apparatus, consisting of tow haploid synergids on either side of a large, central, haploid egg cell.
8.DEVELOPMENT OF FEMALE GAMETOPHYTE PICTURE.
Thank You.
The "Telome theory" of Walter Zimmermann (1930, 1952) is the most accepted theory that is based on fossil record and synthesizes the major steps in the evolution of vascular plants.
It describes how the primitive type of vascular plants developed from Rhynia like plants.
Wall layers of anther have different functions most importantly they help in providing nutrition to developing pollens and also help in anther dehiscence.
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.
1. INTRODUCTION
A gametophyte is a stage in the life cycle of plants and algae that undergo alternation of generations.
The gametophyte is the sexual phase in the life cycle of plants and algae.
Cell division of the zygote results in a new diploid multicellular organism, the second stage in the life cycle known as the sporophyte, the function of which is to produce haploid spores by meiosis.
2. Structure of Female Gametophyte
The female gametophyte is also called the embryo sac.
In angiosperms it mostly develops as a seven celled, eight-nucleate structure.
It consists of three antipodal cells, one central cell, two synergid cells, and one egg cell mostly.
3.Structure of Female Gametophyte
It generally contain antipodal cells at chalazal ends, an egg cell and two synergids at microplyar ends, and a center containing two polar nuclei.
Embryo sec is expect the center binucleate cell.
The process of formation of embryo sac is known as megasporogenesis.
4.The female gametophyte first arise as a tiny protuberance from the placenta, in the cavity of the overy.
As it mature,the ovule consists of a nutritive cellular mass known as nucellus, protected by two integuments, and attached to the placenta by a funiculus.
Even at an early stage, one cell becomes evident in the nucellus, which is known as the megaspore mother cell(MMC).
5.MMC is diploid (2n)
The MMC then increases in size, and divides twice (meiotically) to from 4 megaspore as ‘linear tetrad’
The first division is a reduction division
The resultant megaspores are haploid (n)
Out of the four megaspores, three degenerate, forming caps, while one remains functional.
6.This functionl megaspore is haploid (n)
The functional megaspore, then grows rapidally, by absorbing nutrition from nucellus, and forms the embryo sac.
The process of formation of embryo sac is known as megasporogenesis.
The embryo sac consists of one nucleus.
The nucleus divided into two daughter nuclei, which move towards the poles.
The pole of the embryo sac, closer to the chalaza, is the chalazal end,and the one closer to the microphyle is the micropylar end.
7.Each daughter nuclei divides again, and result in four nuclei.
Each nuclei divides again, for the last time, and result in eight nuclei.
One nuclei from each end, come to the centre, and fuse to from a diploid secondary nucleus.
The nuclei at the chalazal end, get surronded by cytoplasm, and form three distinct, haploid, antipodal cells.
Similarly, the nuclei at the micropylar end, form the egg apparatus, consisting of tow haploid synergids on either side of a large, central, haploid egg cell.
8.DEVELOPMENT OF FEMALE GAMETOPHYTE PICTURE.
Thank You.
This upload includes description of structure of microsporangium, microsporogenesis, pollen grain and megasporogenesis.
It will be helpful to the students for their quick reference.
Class 12||Chapter 2|| Sexual Reproduction in flowering plantsPrathamBiology
This chapter includes flowers, their detailed structure and developmental processess which took place durin sexual reproduction. Helpful for Board and NEET students.
Fell free for any query or suggestion
Mail us on: biologypratham@gmail.com
Website : www.prathambiology.in
The Slides contains are Female Reproductive part of Flower (Carpels/Pistils), Structure of Ovule, Types of Ovules, Microsporogenesis, Megasporogenesis, Structure of Pollen Grain, Structure of Embryo Sac
Reproduction ensures continuity of species generation after generations as the older individuals undergo senescence and die. Flowering plants shows sexual mode of reproduction and bears complex reproductive units as male and female reproductive units along with accessary structures.
Flower is a modified stem which functions as a reproductive organ and produces ova and/or pollen. A typical angiospermic flower consists of four whorls of floral appendages attached on the receptacle: calyx, corolla, androecium (male reproductive organ consisting of stamens) and gynoecium (composed of ovary, style and stigma) .
Table of Contents:
a. Structure
b. Reproductive Structure
c. Androecium
d. Microsporogenesis
e. Gynoecium
f. Megasporogenesis
g. Pollination
h. Fertilization
i. Functions
Explore sexual reproduction in flowering plants notes to learn about the reproductive structure of the flower and the process of pollination.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
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.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
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.
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 .
(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.
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
3. *
A typical stamen-
• the long and slender stalk
called the filament
• the terminal bilobed structure
called the anther.
• Monothecous Hibiscus,
Dithecous brinjal
The proximal end of the filament
is attached to the thalamus or the
petal of the flower.
The number and length of
stamens vary.
3
4. *
Dithecous - anther is bilobed
with each lobe having two theca
A longitudinal groove runs
lengthwise separating the theca.
4
7. *
*Dithecous - bilobed nature
*The anther is a four-sided (tetragonal) structure - four
microsporangia located at the corners, two in each lobe.
*The microsporangia develop- pollen sacs. They extend
longitudinally ,are packed with pollen grains.
*Structure of microsporangium: In T.S. a typical microsporangium
appears circular in outline. It is generally surrounded by four wall
layers -- the epidermis, endothecium, middle layers and the
tapetum.
*The outer three wall layers perform the function of protection
and help in dehiscence of anther to release the pollen.
* The innermost wall layer is the tapetum. It nourishes the
developing pollen grains. Cells of the tapetum possess dense
cytoplasm and generally have more than one nucleus. Nucleus
divides – without cytoplasmic division- polyploidy
7
8. *
*When the anther is young, a group of compactly arranged
homogenous cells -the sporogenous tissue occupies the centre
of each microsporangium.
*The cells of the sporogenous tissue undergo meiotic divisions
to form microspore tetrads. ( haploidy)
8
10. 10
*
*The pollen grains represent the male
gametophytes.
*sizes, shapes, colours, designs- different
species
*fossils because of the presence of
sporopollenin
*Cryopreservation(-196 0C ) used in crop
breeding
*Pollen food nutritional value –
performance of athletes and race horses
*Pollen Allergy, bronchial
*Afflictions, asthma, bronchitis eg
Parthenium
*Viability of pollen grains depends on
temperature and humidity. Viable from
few mins to several months
*– few mins (rice) to few months
(Solanacae), Rosaceae, Leguminoseae
11. 11
*Pollen grain wall- exine and intine
*Exine – thick hard ornamental, made up of sporopollenin
( most resistant organic material high temperature, acid, alkalies)
*Germ pore- circular aperture in exine- spropollenin absent.
Pollen tube emerges from germ pore
*The inner wall of the pollen grain intine- a thin and continuous
layer made up of cellulose and pectin.
13. 13
The cytoplasm of pollen grain is surrounded by a plasma membrane. A
mature pollen grain – ( inside intine and exine )
During development from microspore mitosis – 2 cells
• vegetative cell / tube cell --bigger, has abundant -food reserve and a
large irregularly shaped nucleus.
• generative Cell -- small , spindle shaped with dense cytoplasm & a
nucleus. It floats in the cytoplasm of the vegetative cell.
60 % angiosperms, pollen grains are shed at 2-celled stage.
In others generative cell divides mitotically - the two male gametes
before pollen grains are shed (3-celled stage).
14. 14
*
*Pistil/gynoecium innermost whorl
*Carpel – stigma , style , Ovary
*Ovary many ovule ( megasporangia) attached to a tissue
inside ovary – placenta – ovarian cavity ( locules) –
*Placentation – recap
*number of ovules in an ovary may be one (wheat,
*paddy, mango) to many (papaya, water melon, orchids).
*Monocarpellary / multicarpellary
*Syncarpous ( pistils fused together) , aopcarpous ( free)
16. 16
*
1. Funicle The ovule is attached to the placenta by means of a stalk called
funicle.
2. Hilum The body of the ovule fuses with funicle in the region called
hilum.(hilum - the junction between ovule and funicle)
3. Integuments Each ovule has one or two protective envelopes called
integuments.(inner and outer )
4. Micropyle The integuments leave small opening at one end called micropyle.-
this end is micropylar end.
5. Chalaza Opposite the micropylar end, is the chalaza, representing the basal
part of the ovule.
6. Nucellus Tissue encloses embryo sac
7. Embryo sac
(female
gametophyte)
An ovule generally has a single embryo sac formed from a megaspore
through reduction division.
* Nucleate and 7 celled.
1. Egg apparatus- at micropylar end. It has 2 synergids and an egg.
2. Filiform apparatus- synergids – special thickening at micropylar
end. It guides the pollen tube.
3. Antipodals- 3 in number twds chalazal end.
4. Two Haploid nuclei at polar end below egg appataus
17. 17
* (1) Orthotropous : The micropyle, chalaza
and funicle are in a straight line. This is the
most primitive type of ovule e.g., Piper,
Polygonum, Cycas. - A
*(2) Anatropous : The ovule turns at
180 angle. Thus it is inverted ovule.
Micropyle lies close to hilum or at
side of hilum e.g, found in 90% of
angiosperm families. B
* (3) Campylotropous : Ovule is curved more
or less at right angle to funicle. Micropylar
end is bend down slightly e.g., in members
of Leguminosae, Cruciferae. D
* (4) Hemianatropous : Ovule turns at 90
angle upon the funicle or body of ovule and
is at right angle to the funicle e.g.,
Ranunculus. C
* (5) Amphitropous : Ovule as well as
embryo sac is curved like horse shoe e.g,
Lemna, Poppy, Alisma. E
* (6) Circinotropous : The ovule turns at
more than 360 angle, so funicle becomes
coiled around the ovule e.g., Opuntia
(Cactaceae), Plumbaginaceae. F
18. *
Megaspore
mother cells
MMC
Deploid
Megaspore
haploid
Monosporic
development
Functional
megasopre
to Embryo
sac
Cells in the
nucellus
near
micropylar
region.
Four cells
Haploid
3 near
micropyle
degenerrate
1 functional
megaspore
Meiosis
Mega-
sporogenesis
Functional megaspore enlarges,
mitotic division 2 nuclei – move
opposite poles – 2 mitoic
division- 4 nuclei at each pole
Wall formation only after this
stage
Chalaza end – 3 form antipodals
Micropylar end – 3 form egg
apparatus
Remaining 2 nucei Polar nuclei
in large central cell.
18
20. 20
Functional
megaspore
to Embryo
sac
Functional megaspore enlarges, mitotic division 2
nuclei – move opposite poles – 2 mitoic division- 4
nuclei at each pole
Wall formation only after this stage
Chalaza end – 3 form antipodals
Micropylar end – 3 form egg apparatus
Remaining 2 nucei Polar nuclei in large central cell.
22. 22
*
*All events from deposition of pollen grains on stigma – entry
of pollen tube into the ovule -Pollen pistil interaction
*Identification of compatible (same species) or incompatible(
other species) pollen grains by stigma
*a dynamic process involving pollen recognition followed by
promotion or inhibition of the pollen.
*Reason – chemical interaction between pollen and stigma
*Compatible pollen accepted by stigma, initiates post
pollination events
23. 23
*
*Germination- formation of pollen tube through germ
pore- content move to pollen tube- through stigma, style
reaches ovary
*pollen grains - two-celled condition (a vegetative cell
and a generate cell)- the generative cell divides and
forms the two male gametes during the growth of pollen
tube in the stigma.
*three-celled condition, pollen tubes carry the two male
gametes from the beginning.
*Pollen tube, after reaching the ovary, enters the ovule
through the micropyle and then enters one of the
synergids through the filiform apparatus
*Interaction is important in plant breeding- for superior
plant development
24. 24
*
Pollen tube into
synergid
• the pollen tube releases the two male gametes into the
cytoplasm of the synergid.
Syngamy
• the pollen tube releases the two male gametes into the
cytoplasm of the synergid.
• Diploid Zygote formation - zygote develops into an embryo.
Triple fusion
3 haploid nucleus
fuse
• other male gamete moves towards the two polar nuclei located
in the central cell and fuses with them to produce a triploid
PEN This central cell forms
• primary endosperm cell (PEC) and develops into the endosperm
26. 1 Male gamete fuses
with the 2 polar nuclei
to form the triploid
endosperm nucleus
1 male gamete
fuses with the egg
nucleus to form the
diploid zygote
Double fertilization recap
27. 27
*
*After double fertilization events of endosperm and embryo
development, maturation of ovule(s) into seed(s) and ovary
into fruit, are collectively termed post-fertilisation events.
➢Endosperm development
➢Embryogeny
➢Seed formation
*Endosperm development : Primary Endosperm Cell (Triple
fusion) – Endosperm (3n)
*Endosperm – cells filled with reserved food material -main
source of nutrition for the embryo
28. *
•The endosperm nucleus
(3N) divides repeatedly
to form the endosperm
in endospermic seeds.
This endosperm acts as
a food store for the
developing seed
•e.g. maize
3N
endosperm
nucleus
2N Zygote
29. 29
*
Nuclear
• PEN successive nuclear divisions free nuclei. free-
nuclear endosperm. Nuclei free, the cw formation
afterwards.
Cellular
• First and subsequent divisions followed by cw
formation
Helobial
• In between above two
• Transvrse wall mycropylar and chalazal
chamber
Non persistant embryo in some seeds,& perisperm till germination
30. 30
Embryogeny - Embryo formation – similar in Mono cot and dicot
Embryo develops micropylar end sac where the zygote is situated.
First endosperm develops then zygote. Provision of nutrition taken care
Zygote – proembryo – globular
mature heart shaped embryo
1 st
divisio
n
Transverse division – 2 cells
Cell twds micropyle
embryo/terminal cell
Other – basal cell / suspensor
cell
Suspe
nsor
cell
Transverse division, 6-10 cells
forms suspensor
Terminal cell is swollen,
vesicular Haustorium
Lowermost – hypophysis to root
tip and root cap
31. 31
Embryo cell Vertical division at right angles to one another- 4 cells
then transverse division – 8 cells (octant)
Terminal four to plumule
Towds hypophysis to hypocotyle and radical
Proembryo Undifferntiated , globular
To heart shaped- then maturity
32. Dicot embryo consists of an
embryonal axis and two
cotyledons.
The portion of embryonal axis above
the level of cotyledons is the
epicotyl, which terminates with the
plumule or stem tip.
The cylindrical portion below the
level of cotyledons is hypocotyl that
*terminates at its lower end in the
radical or root tip. The root tip is
covered with a root cap.
32
*
33. *In the grass family the cotyledon is
called scutellum - situated towards
one side (lateral) of the embryonal
axis.
* At its lower end, the embryonal axis
has the radical and root cap enclosed
in an undifferentiated sheath called
coleorrhiza.
*The portion of the embryonal axis
above the level of attachment of
scutellum is the epicotyl. Epicotyl
has a shoot apex and a few leaf
primordia enclosed in a hollow foliar
structure, the coleoptile.
33
*
40. 40
True fruit False fruit Parthenocarpic
Fruit develops only from
the ovary.
Floral parts - the
thalamus also
contributes to fruit
formation. apple,
strawberry, cashew
fruits develop without
fertilisation.
Banana
Refer BASE Book for
details
Induced - application of
growth hormones-
auxins
Seedless Grapes
Dormany importance drying
Advantages of seed for formation BAsE module
41. 41
Non reccurrent
Normal embryo sac
production
Haploid egg/other cell to
embryo
Sterile plants, non recurrent
Recurrent
No meiosis
Diploid nuclei in embryo
Egg/ any cell (2n)
Adenttive/Saprophytic
budding
Embryo from nucellus/
integuments
Apomixis -- seed without fertilization, grasses
Hybrid apomixis discussion
42. 42
*
*More than one embryo in the seed
1. Zygote / proembryo into 2/more units -
then in embryo
2. Embryos from other part of embryo sac than
egg say synergids ( antipodals rare)
3. Cells of nucellus integuments – mango, citrus
4. Multiple embryosac in ovule- all fertilised