SlideShare a Scribd company logo
1 of 18
Download to read offline
HETEROSPORY AND
SEED-HABIT
PRESENTED BY –
SUBHAM SAHA
M.SC 1ST SEM
ROLL NO. - 09
DEPARTMENT OF BOTANY
GAUHATI UNIVERSITY.
CONTENT
INTRODUCTION
HETEROSPORY
ORIGIN OF HETEROSPORY
SIGNIFICANCE OF HETEROSPORY
SEX DIFFERENTIATION
SEED HABIT
ORIGIN OF SEED HABIT
CONCLUSION
REFERENCE
INTRODUCTION
There are some Pteridophytes which produce two different types of
spores. Such Pteridophytes are known as heterosporous and the
phenomenon is known as heterospory.
Heterospory is considered as a pre-requisite of seed formation.
According to Rashid (1976), only 8 living genera of Pteridophytes are
heterosporous.
ORIGIN OF HETEROSPORY
It is universally accepted that homosporous condition is primitive and
heterospory is derived.
The origin of heterospory can be better discussed on the basis of evidences
from paleobotany, developmental and experimental studies.
1. Palaeobotanical evidences:
 It has been suggested that heterospory arose due to degeneration of
some spores in a few sporangia.
 As more nutrition becomes available to less number of spores, the
surviving spore grow better, hence increase in their size.
 Palaeobotanical evidences also shows that the heterosporous
condition appeared subsequently in the lowermost upper Devonian.
 According toWilliamson and Scot (1894), two
species of Calamostachys form the initial stage
that might lead to the heterospory.These
species were C. binneyana and C. casheana.
MICROSPORES
MEGASPORES
2. Evidences from Developmental Studies:
 In heterosporous Pteridophytes the development of micro and
megasporangia follow the same pattern.They have identical
organization but for their size. While in megasporangia most of
the spore mother cells degenerate but in microsporangia only a
few mother cells are disorganize
 The phenomenon of heterospory becomes distinct either before
or after meiosis. In Selaginella, Isoetes it is distinct before
meiosis.
 In Marsilea, Salvinia and Azolla the phenomenon of heterospory
becomes distinct after meiosis
3. Evidences from Experimental Studies:
 Experimental studies on Selaginella (Goebel, 1905) and
Marsilea (Shattuck, 1910) suggest that nutritional factors
mainly govern the heterospory.
 Under conditions of low light intensity, the photosynthetic
activity of Selaginella was retarted and it produced
microsporangia.
 By sudden lowering of the temperature, the size of the
microspores in the sporocarp of Marsilea increases by six
times.
SIGNIFICANCE OF HETEROSPORY
The phenomenon of heterospory is of great biological significance on account
of the following facts:
(i)The development of the female gametophyte starts while the megaspore is still
inside the megasporangium.
(ii) Same is true of microspores i.e., they also start germinating into male
gametophytes while they are still inside microsporangium.
(iii)The female gametophyte derives its nourishment from the sporophyte i.e.,
female gametophyte is dependent on sporophyte for its nourishment.
(iv)The dependence of female gametophyte on sporophyte for its nourishment
provides better starting point for the development of new embryo than an
independent green prothallus which has to manufacture its own food.
SEX DIFFERENTIATION
 In heterospory, the smaller spores i.e. microspores gives rise
to microgametophyte bearing male sex organs.
 And, the larger spores i.e. magaspores develops into
megagametophyte bearing female sex organs.
 It is quite clear that the differentiation in the size of the spore
is directly related to the sex differentiation of the
gametophytes.
 Therefore, heterospory is an expression of sex differentiation
in plants.
 Incipient heterospory is usually found in fossil plants
where different sizes and sexes are found in same
sporangium.
 But the size of the spores are not natural as they have
to be in normal circumstances.
SEED HABIT IN PTERIDOPHYTES
The adoption of heterospory and the retention and germination of a
single megaspore within megasporangium to form a female
gametophyte, led to the phenomenon of “seed habit”, a
characteristic feature of the spermatophytes.
ORIGIN OF SEED HABIT
The origin of seed habit is associated with the following:
(i) Production of two types of spores (heterospory).
(ii) Reduction in the number of megaspores finally to one per megasporangium.
(iii) Retention and germination of the megaspores and fertilization of the egg.
(iv) Continued development of the fertilized egg into the embryo while still in situ.
From the above observations it is concluded that the life
history of Selaginella approaches towards seed habit
because of the following features:
1.The occurrence of the phenomenon of heterospory.
2. Germination of megaspore inside megasporangium.
3. Retention of megaspore inside megasporangium either till the formation
of female gametophyte or even after fertilization.This condition can be
linked with vivipary in some angiosperms.
4. Development of only one megaspore per megasporangium for example,
in Selaginella monospora, S. rupestris, S. erythropus etc.
Though Selaginella as well as lower Spermatophytes
shows homologies in their structure as follows:
Selaginella: LowerSpermatophytes
(Gymnosperms):
1. Megasporangium. 1. Nucellus of ovule.
2. Megaspore. 2. Megaspore(Embryosac).
3. Female gametophyte. 3. Endosperm.
4. Archegonium. 4. Archegonium.
5. Egg. 5. Egg.
Even then the seeds are not formed in Selaginella because:
1. Megasporangium is not surrounded by integument.
2.The retention of megaspore permanently inside the
megasporangium has not been well established.
3.The embryo immediately gives rise to the sporophyte without
undergoing a resting period.
CONCLUSION
 After considering the above conditions, we can conclude
that there is a connecting link between heterosporous
condition and formation of seed habit.
 It is quite possible that some biochemical compounds
determine the sexual behaviors of spores.
 In homosporous spores, the hormones that govern the
male and the female characters are balanced.When the
process of degeneration starts, there will be imbalances
leading to changes in sexual behavior.
 From the above discussions, it is clear that heterospory of
Selaginella plays significant role in the development of
seed-habit and finally from this seed-habit evolution of
seed might have taken place in higher plants.
REFERENCES
 SOURCE : INTERNET
 https://www.alamy.com/studies-in-fossil-botany-paleobotany-calamostachys
 https://www.biologydiscussion.com/pteridophytes/heterospory-and-seed-habit
 https://www.google.com/search?q=seed+habit+in+selaginella
 https://www.easybiologyclass.com/heterospory-and-seed-habitat-in-
pteridophytes
 SOURCE : BOOK
 Botany for degree students : Pteridophytes byVaisistha, kumar & Sinha.
 Studies in Botany volm. 1 by J.N.Mitra, Debabrata Mitra & SalilChowdhury.
THANKYOU
EVERYONE

More Related Content

What's hot

Stelar evolution in Pteridophytes
Stelar evolution in PteridophytesStelar evolution in Pteridophytes
Stelar evolution in PteridophytesJayakara Bhandary
 
Evolution of sporophyte in bryotphytes
Evolution of sporophyte in bryotphytesEvolution of sporophyte in bryotphytes
Evolution of sporophyte in bryotphytesSangeeta Das
 
APOGAMY & APOSPORY.pptx
APOGAMY & APOSPORY.pptxAPOGAMY & APOSPORY.pptx
APOGAMY & APOSPORY.pptxPravinKorePk
 
Structure, reproduction, life history and systematic position of Lycopodium
Structure, reproduction, life history and systematic position of LycopodiumStructure, reproduction, life history and systematic position of Lycopodium
Structure, reproduction, life history and systematic position of LycopodiumSankritaShankarGaonk
 
Classification of pteridophyta
Classification of pteridophytaClassification of pteridophyta
Classification of pteridophytakhadija habib
 
Morphology, Structure and Reproduction of Equisetum.
Morphology, Structure and Reproduction of Equisetum. Morphology, Structure and Reproduction of Equisetum.
Morphology, Structure and Reproduction of Equisetum. Dhaneesh Ram
 
Monographic study of Osmunda.pptx
Monographic study of Osmunda.pptxMonographic study of Osmunda.pptx
Monographic study of Osmunda.pptxShiv kumar patel
 
Root apex organization
Root apex organization Root apex organization
Root apex organization RanaAdnan35
 
Funaria ( bryophytes)
Funaria ( bryophytes)Funaria ( bryophytes)
Funaria ( bryophytes)SyedaFari2
 
phylogenetic evolution of gymnosperms
phylogenetic evolution of gymnospermsphylogenetic evolution of gymnosperms
phylogenetic evolution of gymnospermsrosewind1
 
Morphogenesis in bryophytes
Morphogenesis in bryophytesMorphogenesis in bryophytes
Morphogenesis in bryophytesAnjnaSharma111
 
"Equisetum" Structural development Reproduction
"Equisetum" Structural development Reproduction "Equisetum" Structural development Reproduction
"Equisetum" Structural development Reproduction Muhammad ArSlan
 
General Characters of Gymnosperms.pptx
General Characters of Gymnosperms.pptxGeneral Characters of Gymnosperms.pptx
General Characters of Gymnosperms.pptxAliya Fathima Ilyas
 

What's hot (20)

Cycas
CycasCycas
Cycas
 
Stelar evolution in Pteridophytes
Stelar evolution in PteridophytesStelar evolution in Pteridophytes
Stelar evolution in Pteridophytes
 
Telome Theory
Telome TheoryTelome Theory
Telome Theory
 
Evolution of sporophyte in bryotphytes
Evolution of sporophyte in bryotphytesEvolution of sporophyte in bryotphytes
Evolution of sporophyte in bryotphytes
 
APOGAMY & APOSPORY.pptx
APOGAMY & APOSPORY.pptxAPOGAMY & APOSPORY.pptx
APOGAMY & APOSPORY.pptx
 
Structure, reproduction, life history and systematic position of Lycopodium
Structure, reproduction, life history and systematic position of LycopodiumStructure, reproduction, life history and systematic position of Lycopodium
Structure, reproduction, life history and systematic position of Lycopodium
 
Classification of pteridophyta
Classification of pteridophytaClassification of pteridophyta
Classification of pteridophyta
 
Morphology, Structure and Reproduction of Equisetum.
Morphology, Structure and Reproduction of Equisetum. Morphology, Structure and Reproduction of Equisetum.
Morphology, Structure and Reproduction of Equisetum.
 
Monographic study of Osmunda.pptx
Monographic study of Osmunda.pptxMonographic study of Osmunda.pptx
Monographic study of Osmunda.pptx
 
Root apex organization
Root apex organization Root apex organization
Root apex organization
 
Telome theroy
Telome theroyTelome theroy
Telome theroy
 
Funaria ( bryophytes)
Funaria ( bryophytes)Funaria ( bryophytes)
Funaria ( bryophytes)
 
phylogenetic evolution of gymnosperms
phylogenetic evolution of gymnospermsphylogenetic evolution of gymnosperms
phylogenetic evolution of gymnosperms
 
Morphogenesis in bryophytes
Morphogenesis in bryophytesMorphogenesis in bryophytes
Morphogenesis in bryophytes
 
"Equisetum" Structural development Reproduction
"Equisetum" Structural development Reproduction "Equisetum" Structural development Reproduction
"Equisetum" Structural development Reproduction
 
Marchantia
MarchantiaMarchantia
Marchantia
 
Pteridophyte ppt
Pteridophyte pptPteridophyte ppt
Pteridophyte ppt
 
General Characters of Gymnosperms.pptx
General Characters of Gymnosperms.pptxGeneral Characters of Gymnosperms.pptx
General Characters of Gymnosperms.pptx
 
Shoot Apex
Shoot ApexShoot Apex
Shoot Apex
 
Rhynia
RhyniaRhynia
Rhynia
 

Similar to Heterospory and seed habit by Subham saha

Embryology and taxonomy
Embryology and taxonomyEmbryology and taxonomy
Embryology and taxonomyNavneetkaur678
 
Classification of fungi
Classification of fungiClassification of fungi
Classification of fungiswethamohan17
 
Mucorales (sexual reproduction)
Mucorales (sexual reproduction)Mucorales (sexual reproduction)
Mucorales (sexual reproduction)Sadhna Pandey
 
Different modes of reproduction of fungi and reproductive structure and nutri...
Different modes of reproduction of fungi and reproductive structure and nutri...Different modes of reproduction of fungi and reproductive structure and nutri...
Different modes of reproduction of fungi and reproductive structure and nutri...hassabbinahmed
 
Cytogenetics of apomixis by Suneel kr Gautam
Cytogenetics of apomixis by Suneel kr GautamCytogenetics of apomixis by Suneel kr Gautam
Cytogenetics of apomixis by Suneel kr GautamSuneelkumarGautam
 
Reproduction in algae
Reproduction in algaeReproduction in algae
Reproduction in algaePriya Trivedi
 
Sexual Incompatibility and its types: MSC BOTANY
Sexual Incompatibility and its types: MSC BOTANYSexual Incompatibility and its types: MSC BOTANY
Sexual Incompatibility and its types: MSC BOTANYICSC
 
Spermatogenesis in Nonmammalian Vertebrates
Spermatogenesis in Nonmammalian VertebratesSpermatogenesis in Nonmammalian Vertebrates
Spermatogenesis in Nonmammalian VertebratesCheche Salas
 
General Character of Fungi.pptx
General Character of Fungi.pptxGeneral Character of Fungi.pptx
General Character of Fungi.pptxjeevitha479453
 
reproduction in organisms
reproduction in organismsreproduction in organisms
reproduction in organismsjawedquamer3
 
Alternation of generation in archegoniates
Alternation of generation in archegoniatesAlternation of generation in archegoniates
Alternation of generation in archegoniatesSumit Sangwan
 
Strotler and Crandle classification of bryophyte.pdf
Strotler and Crandle classification of bryophyte.pdfStrotler and Crandle classification of bryophyte.pdf
Strotler and Crandle classification of bryophyte.pdfsohel84
 

Similar to Heterospory and seed habit by Subham saha (20)

Mastigomycotina
MastigomycotinaMastigomycotina
Mastigomycotina
 
Archegoniates
ArchegoniatesArchegoniates
Archegoniates
 
6. reproduction
6. reproduction6. reproduction
6. reproduction
 
INTRODUCTION TO REPRODUCTIVE BIOLOGY OF ANGIOSPERMS 1.pdf
INTRODUCTION TO REPRODUCTIVE BIOLOGY OF ANGIOSPERMS 1.pdfINTRODUCTION TO REPRODUCTIVE BIOLOGY OF ANGIOSPERMS 1.pdf
INTRODUCTION TO REPRODUCTIVE BIOLOGY OF ANGIOSPERMS 1.pdf
 
Embryology and taxonomy
Embryology and taxonomyEmbryology and taxonomy
Embryology and taxonomy
 
Heterothallism
HeterothallismHeterothallism
Heterothallism
 
Classification of fungi
Classification of fungiClassification of fungi
Classification of fungi
 
Mucorales (sexual reproduction)
Mucorales (sexual reproduction)Mucorales (sexual reproduction)
Mucorales (sexual reproduction)
 
Different modes of reproduction of fungi and reproductive structure and nutri...
Different modes of reproduction of fungi and reproductive structure and nutri...Different modes of reproduction of fungi and reproductive structure and nutri...
Different modes of reproduction of fungi and reproductive structure and nutri...
 
Classification of fungi by alexopolus
Classification of fungi by alexopolusClassification of fungi by alexopolus
Classification of fungi by alexopolus
 
Cytogenetics of apomixis by Suneel kr Gautam
Cytogenetics of apomixis by Suneel kr GautamCytogenetics of apomixis by Suneel kr Gautam
Cytogenetics of apomixis by Suneel kr Gautam
 
Fungi Class2.pptx
Fungi Class2.pptxFungi Class2.pptx
Fungi Class2.pptx
 
Reproduction in algae
Reproduction in algaeReproduction in algae
Reproduction in algae
 
Sexual Incompatibility and its types: MSC BOTANY
Sexual Incompatibility and its types: MSC BOTANYSexual Incompatibility and its types: MSC BOTANY
Sexual Incompatibility and its types: MSC BOTANY
 
Spermatogenesis in Nonmammalian Vertebrates
Spermatogenesis in Nonmammalian VertebratesSpermatogenesis in Nonmammalian Vertebrates
Spermatogenesis in Nonmammalian Vertebrates
 
General Character of Fungi.pptx
General Character of Fungi.pptxGeneral Character of Fungi.pptx
General Character of Fungi.pptx
 
reproduction in organisms
reproduction in organismsreproduction in organisms
reproduction in organisms
 
Mycology5 converted
Mycology5 convertedMycology5 converted
Mycology5 converted
 
Alternation of generation in archegoniates
Alternation of generation in archegoniatesAlternation of generation in archegoniates
Alternation of generation in archegoniates
 
Strotler and Crandle classification of bryophyte.pdf
Strotler and Crandle classification of bryophyte.pdfStrotler and Crandle classification of bryophyte.pdf
Strotler and Crandle classification of bryophyte.pdf
 

More from NarayanSarkar6

Cell signaling by Ritima mishra
Cell signaling by Ritima mishraCell signaling by Ritima mishra
Cell signaling by Ritima mishraNarayanSarkar6
 
Cell signaling ion and enzyme linked ritima
Cell signaling ion and enzyme linked ritimaCell signaling ion and enzyme linked ritima
Cell signaling ion and enzyme linked ritimaNarayanSarkar6
 
Seminar dhruba som ( chemotaxis and quorum sensing)
Seminar dhruba som ( chemotaxis and quorum sensing)Seminar dhruba som ( chemotaxis and quorum sensing)
Seminar dhruba som ( chemotaxis and quorum sensing)NarayanSarkar6
 
Chromatography by narayan sarkar and simi baruah new version
Chromatography by  narayan sarkar and simi baruah  new versionChromatography by  narayan sarkar and simi baruah  new version
Chromatography by narayan sarkar and simi baruah new versionNarayanSarkar6
 
Rna editing and r rna processing
Rna editing and r rna processingRna editing and r rna processing
Rna editing and r rna processingNarayanSarkar6
 
Chromatography by narayan sarkar and simi baruah
Chromatography by  narayan sarkar and simi baruahChromatography by  narayan sarkar and simi baruah
Chromatography by narayan sarkar and simi baruahNarayanSarkar6
 

More from NarayanSarkar6 (6)

Cell signaling by Ritima mishra
Cell signaling by Ritima mishraCell signaling by Ritima mishra
Cell signaling by Ritima mishra
 
Cell signaling ion and enzyme linked ritima
Cell signaling ion and enzyme linked ritimaCell signaling ion and enzyme linked ritima
Cell signaling ion and enzyme linked ritima
 
Seminar dhruba som ( chemotaxis and quorum sensing)
Seminar dhruba som ( chemotaxis and quorum sensing)Seminar dhruba som ( chemotaxis and quorum sensing)
Seminar dhruba som ( chemotaxis and quorum sensing)
 
Chromatography by narayan sarkar and simi baruah new version
Chromatography by  narayan sarkar and simi baruah  new versionChromatography by  narayan sarkar and simi baruah  new version
Chromatography by narayan sarkar and simi baruah new version
 
Rna editing and r rna processing
Rna editing and r rna processingRna editing and r rna processing
Rna editing and r rna processing
 
Chromatography by narayan sarkar and simi baruah
Chromatography by  narayan sarkar and simi baruahChromatography by  narayan sarkar and simi baruah
Chromatography by narayan sarkar and simi baruah
 

Recently uploaded

Pests of Sunflower_Binomics_Identification_Dr.UPR
Pests of Sunflower_Binomics_Identification_Dr.UPRPests of Sunflower_Binomics_Identification_Dr.UPR
Pests of Sunflower_Binomics_Identification_Dr.UPRPirithiRaju
 
3.-Acknowledgment-Dedication-Abstract.docx
3.-Acknowledgment-Dedication-Abstract.docx3.-Acknowledgment-Dedication-Abstract.docx
3.-Acknowledgment-Dedication-Abstract.docxUlahVanessaBasa
 
Introduction of Human Body & Structure of cell.pptx
Introduction of Human Body & Structure of cell.pptxIntroduction of Human Body & Structure of cell.pptx
Introduction of Human Body & Structure of cell.pptxMedical College
 
Observational constraints on mergers creating magnetism in massive stars
Observational constraints on mergers creating magnetism in massive starsObservational constraints on mergers creating magnetism in massive stars
Observational constraints on mergers creating magnetism in massive starsSérgio Sacani
 
Advances in AI-driven Image Recognition for Early Detection of Cancer
Advances in AI-driven Image Recognition for Early Detection of CancerAdvances in AI-driven Image Recognition for Early Detection of Cancer
Advances in AI-driven Image Recognition for Early Detection of CancerLuis Miguel Chong Chong
 
Harry Coumnas Thinks That Human Teleportation May Ensure Humanity's Survival
Harry Coumnas Thinks That Human Teleportation May Ensure Humanity's SurvivalHarry Coumnas Thinks That Human Teleportation May Ensure Humanity's Survival
Harry Coumnas Thinks That Human Teleportation May Ensure Humanity's Survivalkevin8smith
 
DETECTION OF MUTATION BY CLB METHOD.pptx
DETECTION OF MUTATION BY CLB METHOD.pptxDETECTION OF MUTATION BY CLB METHOD.pptx
DETECTION OF MUTATION BY CLB METHOD.pptx201bo007
 
GLYCOSIDES Classification Of GLYCOSIDES Chemical Tests Glycosides
GLYCOSIDES Classification Of GLYCOSIDES  Chemical Tests GlycosidesGLYCOSIDES Classification Of GLYCOSIDES  Chemical Tests Glycosides
GLYCOSIDES Classification Of GLYCOSIDES Chemical Tests GlycosidesNandakishor Bhaurao Deshmukh
 
FBI Profiling - Forensic Psychology.pptx
FBI Profiling - Forensic Psychology.pptxFBI Profiling - Forensic Psychology.pptx
FBI Profiling - Forensic Psychology.pptxPayal Shrivastava
 
Think Science: What Are Eclipses (101), by Craig Bobchin
Think Science: What Are Eclipses (101), by Craig BobchinThink Science: What Are Eclipses (101), by Craig Bobchin
Think Science: What Are Eclipses (101), by Craig BobchinNathan Cone
 
Telephone Traffic Engineering Online Lec
Telephone Traffic Engineering Online LecTelephone Traffic Engineering Online Lec
Telephone Traffic Engineering Online Lecfllcampolet
 
complex analysis best book for solving questions.pdf
complex analysis best book for solving questions.pdfcomplex analysis best book for solving questions.pdf
complex analysis best book for solving questions.pdfSubhamKumar3239
 
LAMP PCR.pptx by Dr. Chayanika Das, Ph.D, Veterinary Microbiology
LAMP PCR.pptx by Dr. Chayanika Das, Ph.D, Veterinary MicrobiologyLAMP PCR.pptx by Dr. Chayanika Das, Ph.D, Veterinary Microbiology
LAMP PCR.pptx by Dr. Chayanika Das, Ph.D, Veterinary MicrobiologyChayanika Das
 
Production technology of Brinjal -Solanum melongena
Production technology of Brinjal -Solanum melongenaProduction technology of Brinjal -Solanum melongena
Production technology of Brinjal -Solanum melongenajana861314
 
Total Legal: A “Joint” Journey into the Chemistry of Cannabinoids
Total Legal: A “Joint” Journey into the Chemistry of CannabinoidsTotal Legal: A “Joint” Journey into the Chemistry of Cannabinoids
Total Legal: A “Joint” Journey into the Chemistry of CannabinoidsMarkus Roggen
 
Oxo-Acids of Halogens and their Salts.pptx
Oxo-Acids of Halogens and their Salts.pptxOxo-Acids of Halogens and their Salts.pptx
Oxo-Acids of Halogens and their Salts.pptxfarhanvvdk
 
Role of Gibberellins, mode of action and external applications.pptx
Role of Gibberellins, mode of action and external applications.pptxRole of Gibberellins, mode of action and external applications.pptx
Role of Gibberellins, mode of action and external applications.pptxjana861314
 
Environmental Acoustics- Speech interference level, acoustics calibrator.pptx
Environmental Acoustics- Speech interference level, acoustics calibrator.pptxEnvironmental Acoustics- Speech interference level, acoustics calibrator.pptx
Environmental Acoustics- Speech interference level, acoustics calibrator.pptxpriyankatabhane
 
Combining Asynchronous Task Parallelism and Intel SGX for Secure Deep Learning
Combining Asynchronous Task Parallelism and Intel SGX for Secure Deep LearningCombining Asynchronous Task Parallelism and Intel SGX for Secure Deep Learning
Combining Asynchronous Task Parallelism and Intel SGX for Secure Deep Learningvschiavoni
 

Recently uploaded (20)

Pests of Sunflower_Binomics_Identification_Dr.UPR
Pests of Sunflower_Binomics_Identification_Dr.UPRPests of Sunflower_Binomics_Identification_Dr.UPR
Pests of Sunflower_Binomics_Identification_Dr.UPR
 
3.-Acknowledgment-Dedication-Abstract.docx
3.-Acknowledgment-Dedication-Abstract.docx3.-Acknowledgment-Dedication-Abstract.docx
3.-Acknowledgment-Dedication-Abstract.docx
 
Introduction of Human Body & Structure of cell.pptx
Introduction of Human Body & Structure of cell.pptxIntroduction of Human Body & Structure of cell.pptx
Introduction of Human Body & Structure of cell.pptx
 
Ultrastructure and functions of Chloroplast.pptx
Ultrastructure and functions of Chloroplast.pptxUltrastructure and functions of Chloroplast.pptx
Ultrastructure and functions of Chloroplast.pptx
 
Observational constraints on mergers creating magnetism in massive stars
Observational constraints on mergers creating magnetism in massive starsObservational constraints on mergers creating magnetism in massive stars
Observational constraints on mergers creating magnetism in massive stars
 
Advances in AI-driven Image Recognition for Early Detection of Cancer
Advances in AI-driven Image Recognition for Early Detection of CancerAdvances in AI-driven Image Recognition for Early Detection of Cancer
Advances in AI-driven Image Recognition for Early Detection of Cancer
 
Harry Coumnas Thinks That Human Teleportation May Ensure Humanity's Survival
Harry Coumnas Thinks That Human Teleportation May Ensure Humanity's SurvivalHarry Coumnas Thinks That Human Teleportation May Ensure Humanity's Survival
Harry Coumnas Thinks That Human Teleportation May Ensure Humanity's Survival
 
DETECTION OF MUTATION BY CLB METHOD.pptx
DETECTION OF MUTATION BY CLB METHOD.pptxDETECTION OF MUTATION BY CLB METHOD.pptx
DETECTION OF MUTATION BY CLB METHOD.pptx
 
GLYCOSIDES Classification Of GLYCOSIDES Chemical Tests Glycosides
GLYCOSIDES Classification Of GLYCOSIDES  Chemical Tests GlycosidesGLYCOSIDES Classification Of GLYCOSIDES  Chemical Tests Glycosides
GLYCOSIDES Classification Of GLYCOSIDES Chemical Tests Glycosides
 
FBI Profiling - Forensic Psychology.pptx
FBI Profiling - Forensic Psychology.pptxFBI Profiling - Forensic Psychology.pptx
FBI Profiling - Forensic Psychology.pptx
 
Think Science: What Are Eclipses (101), by Craig Bobchin
Think Science: What Are Eclipses (101), by Craig BobchinThink Science: What Are Eclipses (101), by Craig Bobchin
Think Science: What Are Eclipses (101), by Craig Bobchin
 
Telephone Traffic Engineering Online Lec
Telephone Traffic Engineering Online LecTelephone Traffic Engineering Online Lec
Telephone Traffic Engineering Online Lec
 
complex analysis best book for solving questions.pdf
complex analysis best book for solving questions.pdfcomplex analysis best book for solving questions.pdf
complex analysis best book for solving questions.pdf
 
LAMP PCR.pptx by Dr. Chayanika Das, Ph.D, Veterinary Microbiology
LAMP PCR.pptx by Dr. Chayanika Das, Ph.D, Veterinary MicrobiologyLAMP PCR.pptx by Dr. Chayanika Das, Ph.D, Veterinary Microbiology
LAMP PCR.pptx by Dr. Chayanika Das, Ph.D, Veterinary Microbiology
 
Production technology of Brinjal -Solanum melongena
Production technology of Brinjal -Solanum melongenaProduction technology of Brinjal -Solanum melongena
Production technology of Brinjal -Solanum melongena
 
Total Legal: A “Joint” Journey into the Chemistry of Cannabinoids
Total Legal: A “Joint” Journey into the Chemistry of CannabinoidsTotal Legal: A “Joint” Journey into the Chemistry of Cannabinoids
Total Legal: A “Joint” Journey into the Chemistry of Cannabinoids
 
Oxo-Acids of Halogens and their Salts.pptx
Oxo-Acids of Halogens and their Salts.pptxOxo-Acids of Halogens and their Salts.pptx
Oxo-Acids of Halogens and their Salts.pptx
 
Role of Gibberellins, mode of action and external applications.pptx
Role of Gibberellins, mode of action and external applications.pptxRole of Gibberellins, mode of action and external applications.pptx
Role of Gibberellins, mode of action and external applications.pptx
 
Environmental Acoustics- Speech interference level, acoustics calibrator.pptx
Environmental Acoustics- Speech interference level, acoustics calibrator.pptxEnvironmental Acoustics- Speech interference level, acoustics calibrator.pptx
Environmental Acoustics- Speech interference level, acoustics calibrator.pptx
 
Combining Asynchronous Task Parallelism and Intel SGX for Secure Deep Learning
Combining Asynchronous Task Parallelism and Intel SGX for Secure Deep LearningCombining Asynchronous Task Parallelism and Intel SGX for Secure Deep Learning
Combining Asynchronous Task Parallelism and Intel SGX for Secure Deep Learning
 

Heterospory and seed habit by Subham saha

  • 1. HETEROSPORY AND SEED-HABIT PRESENTED BY – SUBHAM SAHA M.SC 1ST SEM ROLL NO. - 09 DEPARTMENT OF BOTANY GAUHATI UNIVERSITY.
  • 2. CONTENT INTRODUCTION HETEROSPORY ORIGIN OF HETEROSPORY SIGNIFICANCE OF HETEROSPORY SEX DIFFERENTIATION SEED HABIT ORIGIN OF SEED HABIT CONCLUSION REFERENCE
  • 3. INTRODUCTION There are some Pteridophytes which produce two different types of spores. Such Pteridophytes are known as heterosporous and the phenomenon is known as heterospory. Heterospory is considered as a pre-requisite of seed formation. According to Rashid (1976), only 8 living genera of Pteridophytes are heterosporous.
  • 4. ORIGIN OF HETEROSPORY It is universally accepted that homosporous condition is primitive and heterospory is derived. The origin of heterospory can be better discussed on the basis of evidences from paleobotany, developmental and experimental studies. 1. Palaeobotanical evidences:  It has been suggested that heterospory arose due to degeneration of some spores in a few sporangia.  As more nutrition becomes available to less number of spores, the surviving spore grow better, hence increase in their size.  Palaeobotanical evidences also shows that the heterosporous condition appeared subsequently in the lowermost upper Devonian.
  • 5.  According toWilliamson and Scot (1894), two species of Calamostachys form the initial stage that might lead to the heterospory.These species were C. binneyana and C. casheana. MICROSPORES MEGASPORES
  • 6. 2. Evidences from Developmental Studies:  In heterosporous Pteridophytes the development of micro and megasporangia follow the same pattern.They have identical organization but for their size. While in megasporangia most of the spore mother cells degenerate but in microsporangia only a few mother cells are disorganize  The phenomenon of heterospory becomes distinct either before or after meiosis. In Selaginella, Isoetes it is distinct before meiosis.  In Marsilea, Salvinia and Azolla the phenomenon of heterospory becomes distinct after meiosis
  • 7. 3. Evidences from Experimental Studies:  Experimental studies on Selaginella (Goebel, 1905) and Marsilea (Shattuck, 1910) suggest that nutritional factors mainly govern the heterospory.  Under conditions of low light intensity, the photosynthetic activity of Selaginella was retarted and it produced microsporangia.  By sudden lowering of the temperature, the size of the microspores in the sporocarp of Marsilea increases by six times.
  • 8.
  • 9. SIGNIFICANCE OF HETEROSPORY The phenomenon of heterospory is of great biological significance on account of the following facts: (i)The development of the female gametophyte starts while the megaspore is still inside the megasporangium. (ii) Same is true of microspores i.e., they also start germinating into male gametophytes while they are still inside microsporangium. (iii)The female gametophyte derives its nourishment from the sporophyte i.e., female gametophyte is dependent on sporophyte for its nourishment. (iv)The dependence of female gametophyte on sporophyte for its nourishment provides better starting point for the development of new embryo than an independent green prothallus which has to manufacture its own food.
  • 10. SEX DIFFERENTIATION  In heterospory, the smaller spores i.e. microspores gives rise to microgametophyte bearing male sex organs.  And, the larger spores i.e. magaspores develops into megagametophyte bearing female sex organs.  It is quite clear that the differentiation in the size of the spore is directly related to the sex differentiation of the gametophytes.  Therefore, heterospory is an expression of sex differentiation in plants.
  • 11.  Incipient heterospory is usually found in fossil plants where different sizes and sexes are found in same sporangium.  But the size of the spores are not natural as they have to be in normal circumstances.
  • 12. SEED HABIT IN PTERIDOPHYTES The adoption of heterospory and the retention and germination of a single megaspore within megasporangium to form a female gametophyte, led to the phenomenon of “seed habit”, a characteristic feature of the spermatophytes. ORIGIN OF SEED HABIT The origin of seed habit is associated with the following: (i) Production of two types of spores (heterospory). (ii) Reduction in the number of megaspores finally to one per megasporangium. (iii) Retention and germination of the megaspores and fertilization of the egg. (iv) Continued development of the fertilized egg into the embryo while still in situ.
  • 13. From the above observations it is concluded that the life history of Selaginella approaches towards seed habit because of the following features: 1.The occurrence of the phenomenon of heterospory. 2. Germination of megaspore inside megasporangium. 3. Retention of megaspore inside megasporangium either till the formation of female gametophyte or even after fertilization.This condition can be linked with vivipary in some angiosperms. 4. Development of only one megaspore per megasporangium for example, in Selaginella monospora, S. rupestris, S. erythropus etc.
  • 14. Though Selaginella as well as lower Spermatophytes shows homologies in their structure as follows: Selaginella: LowerSpermatophytes (Gymnosperms): 1. Megasporangium. 1. Nucellus of ovule. 2. Megaspore. 2. Megaspore(Embryosac). 3. Female gametophyte. 3. Endosperm. 4. Archegonium. 4. Archegonium. 5. Egg. 5. Egg.
  • 15. Even then the seeds are not formed in Selaginella because: 1. Megasporangium is not surrounded by integument. 2.The retention of megaspore permanently inside the megasporangium has not been well established. 3.The embryo immediately gives rise to the sporophyte without undergoing a resting period.
  • 16. CONCLUSION  After considering the above conditions, we can conclude that there is a connecting link between heterosporous condition and formation of seed habit.  It is quite possible that some biochemical compounds determine the sexual behaviors of spores.  In homosporous spores, the hormones that govern the male and the female characters are balanced.When the process of degeneration starts, there will be imbalances leading to changes in sexual behavior.  From the above discussions, it is clear that heterospory of Selaginella plays significant role in the development of seed-habit and finally from this seed-habit evolution of seed might have taken place in higher plants.
  • 17. REFERENCES  SOURCE : INTERNET  https://www.alamy.com/studies-in-fossil-botany-paleobotany-calamostachys  https://www.biologydiscussion.com/pteridophytes/heterospory-and-seed-habit  https://www.google.com/search?q=seed+habit+in+selaginella  https://www.easybiologyclass.com/heterospory-and-seed-habitat-in- pteridophytes  SOURCE : BOOK  Botany for degree students : Pteridophytes byVaisistha, kumar & Sinha.  Studies in Botany volm. 1 by J.N.Mitra, Debabrata Mitra & SalilChowdhury.