Everything about photoperiodism from scratch to smart, from the oldest models to the latest models as well as proposed one, exclusive and elusive illustrations and models for proper understanding
Self-incompatibility refers to the inability of a plant with functional pollen to set seeds when self pollinated. It is the failure of pollen from a flower to fertilize the same flower or other flowers of the same plant.
This presentation includes, Single-locus self-incompatibility- {Gametophytic self-incompatibility (GSI) and Sporophytic self-incompatibility (SSI)},2-locus gametophytic self-incompatibility, Heteromorphic self-incompatibility,Cryptic self-incompatibility (CSI) and Late-acting self-incompatibility (LSI).
Everything about photoperiodism from scratch to smart, from the oldest models to the latest models as well as proposed one, exclusive and elusive illustrations and models for proper understanding
Self-incompatibility refers to the inability of a plant with functional pollen to set seeds when self pollinated. It is the failure of pollen from a flower to fertilize the same flower or other flowers of the same plant.
This presentation includes, Single-locus self-incompatibility- {Gametophytic self-incompatibility (GSI) and Sporophytic self-incompatibility (SSI)},2-locus gametophytic self-incompatibility, Heteromorphic self-incompatibility,Cryptic self-incompatibility (CSI) and Late-acting self-incompatibility (LSI).
This presentation describes about the dormancy, types of dormancy (seed dormancy and bud dormancy) as well as methods to overcome the bud and seed dormancy in detail.
photoperiodism its discovery,significance,classifications,mechanism,critical day length,quality of light, night break phenomenon,phytochrome.florigen,floering genes, circadian rhythm
Centres of diversity – types of biodiversity – Centres of origin – Law of homologous series – centers of origin – types of centres of diversity – gene sanctuaries – genetic erosion – main reasons of genetic erosion – extinction – introgression – gene banks – types of gene banks
Seed dormancy is fully explained in this ppt. it includes causes ( dormancy due to hard seed coat, dormancy due to condition of embryo, dormancy due to absence of light, dormancy due to low temperature etc. ) of seed dormancy, types of seed dormancy, various methods to remove seed dormancy like impaction, stratification, scarification, exposure of seed to light
This presentation describes about the dormancy, types of dormancy (seed dormancy and bud dormancy) as well as methods to overcome the bud and seed dormancy in detail.
photoperiodism its discovery,significance,classifications,mechanism,critical day length,quality of light, night break phenomenon,phytochrome.florigen,floering genes, circadian rhythm
Centres of diversity – types of biodiversity – Centres of origin – Law of homologous series – centers of origin – types of centres of diversity – gene sanctuaries – genetic erosion – main reasons of genetic erosion – extinction – introgression – gene banks – types of gene banks
Seed dormancy is fully explained in this ppt. it includes causes ( dormancy due to hard seed coat, dormancy due to condition of embryo, dormancy due to absence of light, dormancy due to low temperature etc. ) of seed dormancy, types of seed dormancy, various methods to remove seed dormancy like impaction, stratification, scarification, exposure of seed to light
Seed propagation, Pollination and fertilization, Seed formation and development, Seed Germination and its process, factors affecting seed germination, Dormancy and its types, Methods to overcome it.
Genetic code, Deciphering of genetic code, properties of genetic code, Initiation & termination of codons, Gene Mutation, non sense codon, release factors, Transition , Trans versions
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
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 .
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
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...!
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
2. CONTENTS
Introduction
Types of Dormancy
Types of Seed Dormancy
Causes of Seed Dormancy
Overcoming of Seed Dormancy
2
(Source:https://www.upol.cz/fileadmin/_processe
d_/4/4/csm_hrach_62f4e13155.jpg)
3. INTRODUCTION
Dormancy :
During the developmental cycle of the plant, at
some phase certain structures like buds, tubers,
seeds, go though a period of temporary
suspension of growth activity or slow down for a
period of time or deep sleep, such a state is
called Dormancy.
This minimizes metabolic activity and therefore
helps an organism to conserve to energy.
Dormant = not active or growing but able to
become active later.
3
4. Wareing (1969) defined dormancy as any phase
in the life cycle of a plant in which active growth
is temporarily suspended.
Seed Dormancy :
It is the incapacity of fully developed, mature,
viable seed to germinate even under favourable
conditions.
In such cases, the completely dry ripe seed is
physiologically inactive and is said to be in a
resting stage.
The seed is called dormant and the phenomenon
is termed dormancy. 4
5. The main reason behind this condition is that
they require a period of rest before being
capable of germination.
This Conditions may vary from days to months
and even years.
5
(Source : https://cdn1.byjus.com/wp-content/uploads/2018/12/Seed-Dormancy.png)
6. TYPES OF DORMANCY
According to wareing (1969) the dormancy
may be two types :
1) Imposed dormancy or quiescence:
The dormancy due to unfavourable
environmental conditions is called imposed
dormancy or quiescence.
2) Innate dormancy or rest :
The dormancy due to conditions within the
dormant plant or organ is called innate
dormancy or rest.
It is a condition in which germination or
growth fails to occur even though the external
environmental conditions are favourable.
6
7. During the entire process, there may be
following three phases of dormancy :
1) Pre-dormancy or early rest :
During these phase, the dormant organ has
capacity to resume growth by various
treatments i.e., capacity of germination or
growth is not completely lost. It is called
predormancy.
2) Full dormancy or mid rest :
When a seed or organ becomes completely
dormant and germination or growth cannot be
induced by changes environmental
conditions, it is called full dormancy or mid
rest.
7
8. 3) Post dormancy or after rest :
When a dormant seed or organ gradually
emerges from full dormancy and in it the
germination or growth can be induced by
changing enviornmental conditions, it is called
post-dormancy or after rest.
The dormancy may be true, relative or
secondary :
1)True dormancy :
When in a seed or organ, the germination or
growth cannot be induced under any set of
environmental conditions, it is called true
dormancy.
8
9. 2) Relative dormancy :
When in a seed, the germination can be
induced under specific conditions even at the
time of its deepest dormancy, it is called
relative dormancy.
3) Secondary dormancy :
When a seed has not fully emerged from
dormancy and is again thrown back into full
dormancy by certain environmental conditions,
e.g., temperature etc., it is called secondary
dormancy. 9
10. TYPES OF SEED DORMANCY
Crocker (1916) divided seed dormancy into
two types :
1) Seed coat induced dormancy :
The dormancy of seeds due to extreme
hardness of seed coat is called seed coat
induced dormancy.
2) Embryo induced dormancy :
The dormancy of seeds due to rudimentary or
complete dormant embryo is called embryo
induced dormancy.
10
11. Other types of dormancy may be –
3) Secondary dormancy :
When the seed become dormant again after
breaking the dormancy, it is called secondary
dormancy.
It may be due to combination of different kinds
of dormancy in a single seed, e.g., Xanthium
pennsylvanicum.
4) Special type of dormancy :
The failure of seedling development is not
always traceable due to dormancy of seed
itself.
11
12. In many of the spring wild plants the
germination of seed takes place but the growth
is restricted due to establishment of young
roots.
Sometimes the system of epicotyl fails to
germinate.
In some cases, the epicotyl may be pushed
through the seed coat but remains dormant.
This dormancy is often broken by exposure to
low temperature.
12
13. According to C. Baskin and J. Baskin (1998;
2004) have proposed a comprehensive
classification system which include five
classes of seed dormancy –
(1) Physiological dormancy
(2) Morphological dormancy
(3) Morpho-physiological dormancy
(4) Physical dormancy
(5) Combinational dormancy
13
14. 1) Physiological dormancy :
Physiological dormancy prevents embryo
growth and seed germination until chemical
changes occur.
It is result of seed requiring some type of
physiological condition to be met in order to
germination.
These chemicals include inhibitors that often
retard embryo growth to the point where it is
not strong enough to break through the seed
coat or other tissues.
14
15. 2) Morphological dormancy :
This class of seed dormancy refers to seed with
under development and differentiated embryos,
this includes embryos in which the cotyledons
and hypocotyls, radical axis are differentiated,
but small in size.
These embryo do not have physiological
dormancy and only require additional time to
grow and germinate.
Commonly, under favourable conditions,
embryos in such seeds begin growth within a
period from a few days to several weeks, and
seeds germinate within 30 days.
15
16. 3) Morpho-physiological dormancy :
In this class, seeds have embryos that are
underdeveloped (in size), but differentiated (e.g.,
into cotyledons and hypocotyls radical) as well
as a physiological component to their dormancy.
Thus, to germinate these seeds require time for
embryo growth and a dormancy breaking
treatment.
Morphological dormancy can be divided into two
types- epicotyls dormancy and double dormancy.
16
( Sources: http://botanico.uclm.es/wp-content/uploads/2015/10/Captura-de-pantalla-2015-10-13-a-las-11.20.21.png)
Double dormancy
17. 4) Physical dormancy :
Seed coats are impermeable in water due to
macrosclereid cells, mucilaginous outer cell
layer or hardened endocarp.
Depth of the puncture to the seed coat
increased, so did the permeability of seed
coat of water.
E.g., Olive, Peach, Plum, Cherry etc.
(hardened endocarp of seed). 17
18. 5) Combinational dormancy :
This class groups seeds with simultaneous
physiological and physical dormancy.
In this case, physiological dormancy is
generally characterized as non- deep.
A cold stratification treatment of seed after
scarification to permit imbibitions is a
common dormancy breaking treatment in this
class of seeds. 18
19. CAUSES OF THE SEED DORMANCY
Bewlay and Black (1994) have divided seed
dormancy into two categories, seed coat based
and embryo based.
The dormancy of seeds may be either due to
single or a combination of many different
following factors.
1) Seed Coat induced dormancy / Hard seed
coat :
The seed coat is mostly formed by the
integumentary layers of ovules.
The seed coat consists of two layers – the
outer is testa and the inner is tegmen.
19
20. The testa particularly is composed of a
complex mixture of polysaccharides,
hemicelluloses, fats, waxes and proteins.
During the maturity of seed dehydration takes
place in the seed coat and thus it forms a tuff
protective layer.
Hard seed coat prevents germination due to
following reasons.
(i) Water impermeability :
Seed coats of many plants belonging to
families Leguminosae, Chenopodiaceae,
Malvaceae, Convolvulaceae, Solanaceae and
Nymphaeaceae etc. have very hard seed coats
so, it cannot permeable to entry of water in
seed.
20
21. (ii) Gas impermeability :
The seed coat of certain seeds are
impermiable to gases such as oxygen(o2)
and carbon-di-oxide (co2).
Since oxygen is required for early
respiratory activity in germinating seeds, the
seeds fail to prolong germination.
e.g., Xanthium.
iii) Mechanical resistance :
In certain wild plants the such hard and
tough seed coat physically prevents the
expantion of the embryo. Thus they remain
dormant.
E.g., Alisma, Amaranthus, Capsella etc.
21
22. 2) Embryo Induced Dormancy :
Dormancy due to embryo condition may be of
two types-
(i) Rudimentary and poorly developed embryo
(ii) Embryo fully developed but unable to resume
growth.
(i) Rudimentary and poorly developed embryo :
Instance the embryos are still immature and
rudimentary when the seeds are dispersed.
This is seen in many species like Anemone
nemorosa, Ginkgo biloba, members of
Orchidaceae, Orobanchaceae etc.
In such seeds the embryo does not develop
as rapidly as surrounding tissues.
22
23. (ii) Embryo fully developed but unable to resume
growth :
In many species, e.g., Seeds of apple, peach,
Iris, cherry, tulip, poplar, pines, peas, etc.,
although the embryos are completely
developed in ripe seed but the seeds fails to
germinate even when the environmental
conditions for germinations are favourable.
The embryo of such seeds does not germinate
even if the seed coats are removed.
The germination in such seeds can be induced
if they are stored in moist, well aerated and low
temperature conditions. This process is called
Stratification or after- ripening.
23
24. 3) Dormancy due to Specific Light Requirement :
The seeds of certain plant species such as
Lactona sativa, Lythrum salicaria, Nicotiana
tabacum etc. have specific light requirement for
germination.
Light not only qualitatively but also quanti-
tativly.
The germination of certain seeds requires a
specific photoperiod, e.g., Bignonia requires a
photoperiod of 12 or more hours for seed
germination.
The light sensitive seeds are called photoblastic.24
25. 4) Dormancy due to Germination Inhibitors :
Seeds of certain plants contain compounds
which inhibit their germination. Such natural
germination inhibitors have been found in the
pulp of the fruits, seed coat, endosperm and
embryos or structures surrounding them etc.
(e.g., in tomatoes, in glumes of Oats etc.).
A number of chemical substunces such as
organic acids, phenolics, tannins, alkaloids,
unsaturated lactones, ammonia and cyanide
releasing substunces, indoles and gibberellins
etc. have isolated from seed which are
germination inhibitors. Besides, other inhibitors
are ABA, ammonia, phthalides, coumarin and
parascorbic acid.
25
26. OVERCOMING OF SEED DORMANCY
The dormancy of seeds, though very useful to
man, is not liked by the farmers who would like
the seeds to germinate soon after they have
been harvested.
A number of methods are, therefore, employed
for the breaking of dormancy. The methods
employed vary from species to species
depending upon the cause of the dormancy.
There are main two types of overcoming of seed
dormancy :
1) Natural overcoming of seed dormancy
2) Artificial overcoming of seed dormancy
26
27. 1) Natural overcoming of seed dormancy :
Nature of dormancy stops when the embryo
gets appropriate environment such as adaptive
moisture and temperature.
The seed coat that exists in many species
becomes permeable due to the rupturing of
smoothing action of natural agents like
microorganism, temperature and abrasion by
the digestive tracts of birds and animals that
feed on these seed.
Completion of over-ripening period. 27
28. Leaching of inhibitors present in the seed coat.
Inactivation or oxidation of inhibitors by heat,
cold and light.
Production of growth hormones which can
counteract the effect of inhibitors.
Attainment of maturity of embryo in case the
dormancy is due to incomplete development of
embryo.
28
29. 2) Artificial over coming of seed dormancy :
i) Scarification :
The method is used for breaking dormancy of
seeds caused by hard seed coats which
become impermeable to water and gases etc.
The method employed in softening or
weakening the seed coat is called
Scarification.
When mechanical breaking of seed coat is
done at one or more places, it is called
Mechanical Scarification.
Mechanical Scarification is done by shaking
the seeds with sand or by scratching or
nicking the seed coat with knife.
29
30. The treatment of seed coat with strong mineral
acids or other chemicals is called Chemical
Scarification.
Chemical scarification is usually done by
dipping the seed into strong acids like H2SO4 or
into organic solvents like acetone or alcohol.
It can also be done by boiling the seeds in water.
30
Sources :(http://www.culture-acre.com/wp-
content/uploads/2017/07/seed-
scarification.jpg)
(Sources : http://www.usa-
gardening.com/seed-
scarification/germinating-seeds/scarification-
techniques.jpg)
(Sources:https://image.slidesharecdn.com/bo
tanyforgardeners-2014-final-140202175042-
phpapp02/95/botany-for-gardeners-2014-70-
638.jpg?cb=1391363643)
Scratching by Knife Shaking by Sandpaper By Chemical
32. ii) Stratification:
This method is used to
break the dormancy of
seeds caused due to
condition of embryo.
In this process the seeds
are exposed to well
aerated, moist conditions
under low temperature
(0°C to 10°C) for weeks
to months. This treatment
is called Stratification or
after-ripening. 32(Sources:https://image.slidesharecdn.com/methodsfor
breakingseeddormancy-150208101506-conversion-
gate02/95/methods-for-breaking-seed-dormancy-5-
638.jpg?cb=1423390603)
33. During this treatment, anatomical and
biochemical changes takes place in the seed.
Growth promoting hormones increases and
growth retarding hormones decreases.
iii) Alternating temperature :
In some seeds, the dormancy is broken by the
treatment of an alternating low and high
temperatures.e.g., Poa pratensis
The difference between the alternating
temperature should not be more than 10°C-
20°C.
This method is beneficial in those seeds in
which the dormancy is due to immature
embryos.
33
34. Alternating temperatures of 15°C and 25°C is
useful in breaking the dormancy of photoblastic
seeds like Rumex crispus.
iv) Impaction :
In some of the seeds a strophiolar plug blocks
(testa pores) the entry of water and oxygen into
the seed.
In order to remove the plugs the seeds are
shaken vigoursly and this treatment is known
as Impaction.
E.g., Crotolaria, Trigonella
seed. 34
(Source : https://classconnection.s3.amazonaws.com/345/flashcards/6176345/gif/seedia-148D474B9CE6A431CC3.gif)
35. v) Light :
Dormancy of photoblastic seeds can be over-
come by light exposure.
In positive photoblastic plants light induces
germination. E.g., Amaranthus, Betula,
Capsella, Epilobium, Lactuca etc.
The dormancy of positive photoblastic seeds
can be broken by exposing them to red light
(660 nm). E.g., Lactuca sativa.
In negative photoblastic plants light infact
prevents germination.
In such cases seeds have to be stored in dark
for some time and allow to germinate in
darkness before they are shifted to light.
35
36. vi) Pressure :
Davies (1928) reported the seed germination in
certain plants like sweet clover (Melilotus alba)
and alfalfa (Medicago sativa) can be greatly
improved after being subjected to hydraulic
pressure of about 2000 atm. at 18°C for about
5-20 minutes.
It is strongly believed that the pressure
increases the permeability of the seed coats to
water.
36
37. vii) Growth Regulators :
Kinetins and gibberellins have been used to
induce germination in positively photoblastic
seeds like lettuce and tobacco etc.
Counteracting the effect of growth inhibitory
by soaking the seeds in KNO3, ethylene
chlorohydrin, thiourea, gibberellins.
37
(Source : https://historicjamestowne.org/wp-content/uploads/tobaccoseed.jpg)
Tobacco seed
38. 1) A textbook of Plant Physiology, Biochemistry
and Biotechnology
Author : S.K. Verma, Mohit Verma
Edition : 2007 (Sixth Edition)
2) Textbook of Plant Physiology
Author : V. Verma
Edition : 2007 (First Edition)
3) www.biologydiscussion.com
4) www.slideshare.net
38
References