AUDIENCE THEORY -CULTIVATION THEORY - GERBNER.pptx
Reproduction in organism 2014 mohanbio
1.
2. Reproduction in organism.
• Introduction:
• The period of birth to natural death of an
organism is called life span.
• Life span of organisms vary from species to
species.
• No individual is immortal except unicellular
organism. Because it continue its life in
progeny by fission.
7. The continuity of life on earth is achieved by the
process of reproduction.
8. • Reproduction: It is a biological process in which an
organism produces young ones or offspring.
• Reproduction enables the continuity of species
generation after generation.
• Importance of reproduction:
• Is necessary for continuity of a species.
• Sexual reproduction is responsible for variation in
population and evolution.
• Types of reproduction:
• Asexual reproduction: It is the reproduction by
single parent with out formation of gametes.
• Sexual reproduction: It is the reproduction, in which
two parents of opposite sex involves with the
formation and fusion of gametes.
9. Asexual reproduction.
• The offspring developed by asexual reproduction
are exact copy of their parent. They are
genetically identical. Hence they are termed as
clones.
• Asexual reproduction is common in unicellular
organism. In plants and animals having simple
organizations shows asexual reproduction .
• Binary fission: The single cell organism of
kingdom Monera and Protista reproduce by
binary fission. The cell divides in to two half.
Each half develops in to new adult.
11. • Bud: In yeast the cell
division is unequal and
small buds are produced.
Initially these are attached
to parent cells. Later
separates and develops
into new individual.
• In hydra small outgrowth
forms bud.
12. • Spore formation:
• Zoospores: These are
motile asexual spores
of algae, fungi. They
use flagellum for
locomotion.
13. • Conidia: These are
the asexual non
motile spores of
fungus generated by
mitosis.
• Ex: penicillium.
• In phylum
Ascomycota (sac
fungi)conidia
develops on special
stalk conidiophores.
14. • Gemmules: These are
the internal buds of
fresh water sponges
develops asexualy.
They resist drought,
high temp, freezing,
lac of oxygen etc.
15. Vegetative reproduction
• Asexual reproduction in plants is termed as
vegetative reproduction. In this new plants are
formed by vegetative parts of plant like stem,
root, leaf etc.
• Naturally it occurs by
1. Runner.
2. Rhizome.
3. Suckers.
4. Tuber.
5. Offset.
6. Bulb etc.
16. • Runner or stolon: It is
slender stem that grows
horizontally to ground.
Naturally it cut off and
separated develops in to
new plant.
• Ex: strawberry.
17. • Rhizome: It is the
modified underground
stem.
• If a rhizome is separated
into pieces, each piece
develops into a new
plant.
• Ex: Ginger. Canna
18. • Suckers: It is a basal
shoot, root sprout,
adventitious shoot. It
grows from a bud at
the base of a tree or
shrub or from its
roots.
• Ex: Cherry. Apple.
Mint.
19. • Tuber: Tubers modified plant
structures that are enlarged
to store nutrients.
• These are short, thickened
underground stem.
• It bears minute scale leaves
with a bud called eyes. It has
the ability for developing
into a new plant.
• Ex: Potato
20. • Offset: Offset is a
small complete
daughter plant that
asexually produced
on the mother plant.
• Ex: water hyacinth.
21. • Bulb: Bulb is a
short stem with
fleshy leaves or
leaf bases.
• Ex: Onion, Garlic
etc.
22. • Terror of Bengal:
• Aquatic plant
“Water hyacianth”
( Eichhornia) is
considered as
terror of Bengal. It
was first
introduced in India
because of
beautiful flower
and shape of leaf.
23. • It rapidly reproduced by
vegetative method
offset in short period. It
drains Oxygen from
water that leads to
death of fishes. Hence it
considered as water
weed.
24. Sexual reproduction
• It involves the formation and fusion of male and female
gametes.
• The gametes develops in same individual are bisexual and
different individual are unisexual.
• Bisexual are also called monoecious.
• Unisexual are also called dioecious.
25. • Example for Bisexual or monoecious animals is
earth worm and plant is Chara.
26. • Example for Unisexual or dioecious animal is
cockroach and plant Marchantia (Bryophyte).
27. • All organism reaches the stage of growth and
maturity before they reproduce sexually.
• Juvenile phase: In animals , the period of growth to
attain maturity is called juvenile phase.
• In plants juvenile phase is called vegetative phase.
• In angiosperms end of vegetative phase completes
as soon as they start flowering.
28. • Senescent phase: The end of reproductive phase
is called senescent phase or old age. After this
individual dies up.
flowering in plants:
• The annual plants flowers once in a year. The
biannual plants flowers twice in a year. In these
plants vegetative, reproduction and senescent
phase are clearly identified.
Ex: Rice, wheat, marigold etc.
• In some plants flowering occurs several times in
particular season.
• In some plants flowering occurs only once in a life
time. After that plats dies up.
29. • Ex: bamboo flowering
after 50 to 100 years.
• Kuranji ( strobilanthus
kunthiana) flowers
once in 12 years.
30. Reproductive cycles in animals.
• Reproduction in animals is seasonal. Birds lay
eggs only in specific season.
• The placental animals exhibits reproductive
cycle that leads to change in ovaries and
hormones level.
31. • Oestrus cycle:
• It is the reproductive cycle of non primates
animals like cow. dogs, rats, tigers etc.
• These animals are reproductively active only
in specific season. Hence these are called
seasonal breeders.
• Menstrual cycle: it is the reproductive cycle of
primates like monkeys, apes and human these
are reproductively active through out their
reproductive phase.
• Hence these are called continues breeders.
32. • Events in sexual reproduction:
• 1. Pre fertilization event: It involves the gametogenesis
and gamete transfer.
• 2. Fertilization and Syngamy: Fusion of male and
female gamete.
• 3. Post fertilization event: It involves the formation of
zygote and embryogenesis.
• Pre fertilization events:
• Gametogenesis: It is the process of formation of male
and female haploid gametes.
• Spermatogenesis: It is the process of formation of male
haploid gametes
• Oogenesis: It is the process of formation of female
haploid gametes.
33. • Homogametes or isogametes: The male and female
gametes are morphologically similar in appearance.
• Heterogametes : : The male and female gametes
are morphologically different in appearance.
• Anthrozoid or sperm: male gamete.
• Egg or ovum: female gamete.
34. • Sexuality in plants
• Homothallic or
monoecious: It is the
bisexual condition in fungi,
and plant.
• In this both male and
female reproductive
structure are present in
single individual.
• In most of flowering plants
both type of sex organ
present in the same plant.
• Ex: cucurbita.
• In coconut and maize, male
and female flowers are
present in same plant.
35. • Heterothelic or diecious:
It is the unisexual condition
in plants. In this male and
female reproductive parts
are found in different
flower produced in
different plants.
• Ex : Popaya. Cycas.
• Male flower – staminate
bears only stamens.
• Female flower – pistillate
bears only pistils.
36. • Sexuality in animals:
• Hermaphrodite or
bisexual animals:
• Animals having both
male and female
reproductive organs.
• Ex: Tape worm. Earth
worm. Sponges, leach
etc.
37. • Unisexual animals: Animals having only male
or female reproductive organ. Cockroach.
Insects. Birds. Fishes. Amphibians. Mammals.
38. • Haploid organism: The individual having only one
set of chromosomes in somatic cells are called
haploid organism..
• Monera. Fungi, algae, bryophytes has haploid plant
body. The male honey bee is haploid.
• The haploid organism produce gametes by mitosis.
39. • Honey bee: The male honey bee is also called drones.
These are developed by unfertilized eggs. Hence they are
haploid. They produce haploid gamete by mitosis.
• The female workers are diploid. The queen honey bee is
developed by feeding royal jelly.
• The queen honey bee produces haploid female gamete by
meiosis. The unfertilized eggs develops in to male. The
fertilized egg develops in to female workers
40. • Diploid organism: The individual having two set of
chromosomes in somatic cells.
• Pteridophytes. Gymnosperms. Angiosperms and
most of animals.
• The diploid organisms produce gametes by meiosis.
At the end of meiosis haploid gametes forms.
• Meiocytes: These are diploid gamete mother cells
that undergoes meiosis to produce haploid
gametes.
41.
42. Transfer of gametes.
• In majority of organisms male gametes are
motile. Female gametes are non-motile. In few
fungus and algae both male and female
gametes are motile.
• In algae, bryophytes and pteridophytes male
gametes moves in water to reach female
gamete.
• The large number of male gamete are fails to
reach female gamete. To compensate this loss,
male gametes are produces several thousand
times to female gamete.
43. • In bisexual self fertilizing plants pollen grains
are easily transferred to stigma.
• In unisexual and cross fertilizing plants
pollination occurs by media like air, insects, bird
etc.
44. • Fertilization or syngamy: It is the process of fusion
of male and female gametes that result in the
formation of zygote.
• Parthenogenisis: It is the development of new
individual with out fertilization.
• Ex: Male honey bee. Some lizards. Turkey bird etc.
• The seed less fruits are parthenocarpic fruits.
45. • External fertilization: The fusion of male and
female gamete occurs outside the body, in water
media is called external fertilization.
• Ex: aquatic organism like algae, fishes. Amphibians.
• The dis advantages of external fertilization:
1. Organism should produces large number of
gametes.
2. The predators destroys eggs and off-springs.
3. The survival rate of offspring to adult is very less.
46. • Internal fertilization: The fusion of male and female
gamete occurs inside the female body is called
internal fertilization.
• Ex: Seed plants ( gymnosperms and angiosperms).
Terrestrial animals like reptiles,birds, mammals.
47. • Zygote: The fusion of haploid male and female
gamete result in the formation of diploid zygote.
• In fungi and algae the zygote formed contains
thick cell wall. It helps to resists the unfavorable
condition.
48. • In haplontic ( algae like volvex, spirogyra,
chlamydomanas) zygote divides by meiosis to
form haploid spores. These spores develops into
haploid gametophyte.
49. • In diplontic plant (Gymnosperms and
angiosperms) zygote undergoes mitosis to
develops into diploid dominant sporophyte.
50. • In haplo diplontic plants ( Bryophytes and
pteridophytes) zygote undergoes mitosis to
develops into diploid sporophyte.
51. • Embryogenesis:
• The process of development of embryo from
zygote is called embryogenisis. The zygote
undergoes mitosis division and differentiation into
embryo.
52. • Oviparous :
• The egg laying animals are called
oviparous.
• Ex: Insects, fish, amphibians,
reptiles and birds. Among
mammals prototheria ( egg laying
mammal = Echidna, platypus).
• They lay egg in safe environment.
After incubation young one
hatches out.
• In oviparous embryogenesis takes
place outside the body.
• Hence in reptiles and birds the
fertilization is internal
development is external.
53. • Viviparous : The animals that gives birth to
young one are called viviparous.
• Ex: All mammals except prototheria ( egg laying
mammal) are viviparous.
54. • These are also called placental animals.
• In these embryogenesis takes place inside the female
body. The nutrition and oxygen supplied to developing
embryo from mother through placenta.
• Because of proper embryo care, nutrition and
protection the chance of survival of young one are
more in viviparous than oviparous.
55. • Ovoviviparous.
• The animals in which embryo develops in egg with
in the mother's body until they are ready to hatch.
But there is no placental attachment.
• Ex: few amphibians, fishes like basking shark. Some
reptiles like snakes.
56. • Post fertilization
changes in flower.
• After zygote
formation, the sepals,
petals and stamens of
flower falls off.
• In some plants like
tomato, brinjal sepals
persist with fruit.
• The zygote develops
into embryo.
• The ovule develops
into seed.
• The ovary develops
into fruit (pericarp).
57.
58. Sexual reproduction in flowering
plants.
• Flower is the reproductive
part of angiosperms.
• The flower contains four
whorls attached to thalamus.
• Calyx: It is the outer most
whorl of flower contains
sepals. They protects the
flower in bud condition.
• Corolla: It is the second whorl
of flower contains petals.
These are colored to attract
insects.
59. • The reproductive
structures of flower are
androecium and
gynoecium.
• Androecium: It is the third
whorl of flower contains
stamens. These are male
reproductive structure.
• It produces microscopic
pollen grains that contains
male gamete.
• Gynoecium: It is the
fourth whorl of flower
contains pistils.
60. • Stamen: It has slender stalk
called filament. At the tip it
contains a bilobed structure
called anther.
• Generally anthers are bilobed
that contains two theca
(dithecous) separated by
longitudinal grove.
• The T.S of anther consists of
four sided microsporangia two
in each lobe.
• Microsporangia develops in to
pollen sac. Inside this pollen
grains are present.
61.
62. Structure of microsporangia.
• Microsporangium is
surrounded by 4 layers.
1. Epidermis: It is the outer
single layer of protective cells.
2. endothecium: It is a single
layer of cells has the character
of dehiscence. It helps to
release pollen. The
dehiscence character is due
to their hygroscopic nature.
3. Middle layers: It is formed by
3 to 4 layers of cells.
4. Tepetum: It is the inner most
layer of microsporangia. It
provides nutrition to
developing microspores.
65. • Microsporogenesis: The process of formation
of microspores from pollen mother cells
(PMC) by meiosis is called microsporogenesis.
• The pollen mother cell undergoes meiosis to
form cluster of 4 cells called microspore
tetrad.
• As the anther matures, it dehydrates. The
microspores separates and develops into
pollen grains.
66. Pollen grains:
• Pollen grains are spherical in
shape. They are male
gametophyte.
• They possess two layers. Outer
called exine and inner intine.
• The exine is made up of an
organic compound sporopollenin.
It is very hard and resistance
organic compound. No one
enzyme known to be degrade this
one.
• The exine has a prominent pore
called germ pore.
• The intine is made up of cellulose.
67. • As the pollen grain matures, protoplast mitotically
divides into two unequal cells.
• The bigger vegetative cell and smaller generative cell.
• In majority of angiosperms, pollen grains released as
two cell stage.
• Later generative cell divides mitotically in to two male
gamete.
68. Gynoecium
• Gynoecium is the female
reproductive part of the
flower.
• It consist of pistil.
• monocarpellary :
Gynoecium consists of
single pistil.
• Multicarpellary:
Gynoecium consists more
than one pistil.
• Syncarpous: Gynoecium
with fused pistil.
• Apocarpous: Gynoecium
with free pistil.
72. Pistil
• Each pistil has three
parts - the stigma, style
and ovary.
• Stigma: Stigma is the tip
of pistil. It serves as a
landing platform for
pollen grains.
• Style: Style is the
elongated slender part
present beneath the
stigma.
• Ovary: Ovary is the basal
bulged part of the pistil.
73. • The cavity present
Inside the ovary is
called ovarian cavity
(locule).
• The megasporangia
commonly called
ovules arises from the
placenta.
• The number of ovules
in an ovary may be one
(wheat, paddy, mango)
or many (papaya, water
melon, orchids).
74. Megasporangium (Ovule) :
• Ovule is a female
megasporangium
present in the
ovarian cavity.
• It is small structure
attached to the
placenta with stalk
called funicle.
• The body of the
ovule fuses with
funicle region is
called hilum.
75.
76. • Each ovule is
surrounded by one or
two protective layers
called integuments.
• Integuments encircle
the ovule except at
the tip.
• The small opening
present at tip of ovule
is called micropyle.
• The basal part of the
ovule opposite to the
micropylar end is
called chalaza.
77. • The integument
Encloses a mass of
cells called the
nucellus.
• These cells have
abundant reserve
food materials.
• The embryo sac or
female
gametophyte is
located in the
nucellus.
• An ovule generally
has a single embryo
sac formed from a
megaspore mother
cell through
reduction division.
78. Megasporogenesis
• The process of formation
of megaspores from the
megaspore mother cell is
called megasporogenesis.
• Ovule contains
differentiate single
diploid megaspore
mother cell (MMC) at the
micropylar region of the
nucellus.
• The MMC undergoes
meiotic division. As a
result four haploid cells
forms.
79. • The linear arrangement of four cells is called
linear tetrad.
• Among four cells, one of the megaspores is
functional while the other three degenerate.
• Only the functional megaspore develops into
the female gametophyte.
80. • Megagametogenesis:
• The process of formation of female gametophyte (embryo
sac) from megaspore is called megagametogenesis.
• The nucleus of the functional megaspore divides
mitotically to form two nuclei.
• These two nuclei moves to the opposite poles, forming the
2-nucleate embryo sac.
• Two more sequential mitotic nuclear divisions result in the
formation 4- nucleated and than 8-nucleate stage of
embryo sac.
81. • Two nuclei, one
nucleus from each
pole comes to the
center of embryo sac
are called polar
nuclei.
• Later they fuse
together to form
diploid secondary
nucleus.
• The three nuclei at
the chalazal end are
surrounded by
cytoplasm and cell
wall. These are called
antipodal.
82. • The three nuclei at
the micropylar end
organise in to egg
apparatus.
• They are identified in
to two synergids and
an egg between
them.
• The angiosperm
embryo sac, at
maturity called as 8-
nucleate has 7-celled.
83. • Note:
• Funicle: Stalk of ovule is called funicle.
• Hilum: the region where body of ovule attaches to
funicle is called hilum.
• Integument: The protective layer that surrounds ovule
is called integument.
• Micropyle: The small opening present at tip of ovule is
called micropyle.
• Chalaza: The basal part of ovule opposite to micropyle
is called chalaza.
• Nucellus: The nutritive tissue enclosed in integument
that nourishes the female gametophyte is called
nucellus.
• The nucellus is diploid.
• Megaspore mother cell is diploid.
• Megaspore is haploid.
84. • Polar nuclei: The two central nuclei present in
embryo sac are called polar nuclei.
• Antipodals: Three nuclei present at chalzal end
surrounded by cytoplasm and cell wall are called
antipodals.
• Synergids: the two large cell present adjacent to
ovum or egg at micropyle region are called
synergids.
85.
86. Pollination
• Transfer of pollen grains to
the stigma of a pistil is called
pollination.
• Type:
• Autogamy (self-pollination ):
Transfer of pollen grains from
the anther to the stigma of
the same flower is called
autogamy.
• It takes place by three ways.
1. In Chasmogamous flowers.
2. In Cleistogamous flowers.
3. In Bud pollination.
87. • chasmogamous flowers :
• Flowers with exposed anthers
and stigma are called
chasmogamous flower. In
autogamy anthers and the
stigma lie close to each other.
• Cleistogamous flowers :
• Flowers which do not open are
called cleistogamous flowers.
• Some plants produces both
two types of flowers. Ex: Viola
(common pansy), Commelina
(commonly known as the
Benghal dayflower) and Oxalis.
88. • The sexual reproduction in
Viola occurs via the
chasmogamous flowers in
early Spring and via
cleistogamous flowers in
the summer.
• In Commelina and
peanut(grount nut)
cleistogamy leads to
geocarpy (formation of fruit
in soil).
• Bud pollination: In Wheat,
Tobacco, Tomato, Rice self-
pollination occurs in bud
condition, ie. before the
flower opens.
89. • Geitonogamy –
• Transfer of pollen grains
from the anther to the
stigma of the different
flower of the same plant
is called geitonogamy.
• genetically it is similar to
autogamy because the
pollen grains come from
the same plant.
90. • Xenogamy:
• Transfer of pollen grains
from anther to the stigma
of a different plant of same
species is called xenogamy.
• It is a cross-pollination.
• Agents of Pollination :
Plants use two abiotic (wind
and water) and one biotic
(animals) agents to achieve
pollination.
• Majority of plants use biotic
agents for pollination
92. • Anemophily: The pollination
by wind is called
anemophily.
• Hydrophily: The pollination
by water in hydrophytes is
called hydrophily.
• Zoophily: The pollination by
animals is called zoophily.
93. • On the bases of different
types of animals involved
it is once again classified
into,
• Entamophily: The
pollination by insects is
called entamophily.
• Ornithophily: The
pollination by birdsis
called ornithophily.
• Chirapterophily: The
pollination by bats is
called chirapterophily.
95. • Adaption for anemophily:
• The flowers are small,
nector less, scentless and
never coloured (white
flowers).
• Large amount of pollen
grains are produced.
• Pollen grains are very
small, dry and very light.
• The stigma is sticky and
hairy to trap pollen grains
floating in air.
96. • Hydrophily:
• The pollination by water is called hydrophily. Very few aquatic
plants undergoes hydrophily.
• hypohydrogamic: When the pollination occurs below the
water level is called hypohydrogamic.
• Ex: In Ceratophyllum, Hydrilla.
97. • epihydrogamic: When the pollination occurs
at the water level is called epihydrogamic.
• Ex: In Vallisneria.
98. • In other aquatic plants like water hyacinth
(eichhornia), water lily flower emerges out of
water and pollination occurs by insects.
99. • Hydrophily in vallisneria:
• In vallisneria (sub-merged aquatic plant) the male
flowers opens at the water surface.
• The released pollen grains floats on water current.
• The pedicel of female flower elongates till it reaches
the water surface to contact with pollen grains.
100. • Zoophily: The pollination by animals
like insects, bees, wasp, birds, bats
etc is called zoophily.
• Majority of plants are pollinated by
insects.
• characteristic features of
entamophilous flowers:
• The flowers are fragrant and omits
odour. Ex Jasmine. Rose.
• The flowers are colour full to attract
insects.
• The nectar gland produces nectar to
feed visiting insects.
• The pollen grains are sticky or spiny.
It helps to attach the body of visiting
insects.
• The stigma also sticky to catch pollen
grains .
101. • Pollination in yucca plant:
• Yucca plant is pollinated by moth.
The moth and yucca cannot
complete their life without each
other.
• The moth bores a hole in ovary to
lay its eggs. Then it collects pollen
grains from several flowers and
pushes in the hallow end of
stigma.
• After fertilization and seed
development, the larvae of moth
feed on developing seeds.
• The unconsumed seeds dispersed
to propagation. Thus moth cannot
survive without yucca.
• Yucca cannot reproduce sexually
without moth.
102. • Inbreeding: The fertilization occurs within the single
plant is called inbreeding
• majority of plants are bisexual. The autogamy (self
fertilization) and geitonogamy results in inbreeding.
• Disadvantage of self fertilization or inbreeding:
• The progeny gets weak generation after generation.
It causes decreased fitness in population. It is called
inbreeding depression.
• To avoid this plants developed many device that
discourage self fertilization.
103. • Outbreeding: The fertilization occurs between two
different plants of same species is called outbreeding.
• The xenogamy ( cros- pollination) results in outbreeding.
• Mechanism that plants achieved for outbreeding or
mechanism that discourage self fertilization.
• 1. unisexuality.
• 2. Self-sterility or incompatability.
• 3. Dichogamy.
• 4. Herkogamy.
• unisexuality: The unisexual flowers are produced in same
plant or different plant.
• In monoecious plants with unisexual flowers, like maize,
cucurbita, castor avoids autogamy.
• In dioecious plants like papaya, mulberry unisexuality
results in xenogamy.
104. • Self-sterility or
incompatability: In this pollen
of the same flower has no
fertilizing effect on stigma of
the same flower.
• Ex: Passiflora, potato.
• Dichogamy: It is the condition
that male and female sex organ
of flower matures at different
times.
• a) Protandry: Anthers matures
earlier than gynoecium.
• Ex: china rose, lady’s finger,
jasmine.
• B) protogyny: gynoecium
matures earlier than anther.
• Ex: Custard apple.
105. • Herkogamy: The anther and
stigma are placed at different
position or different height.
So that pollens unable to
reach stigma of same flower.
• Ex: Calotropis. Gloriosa.
106. Artificial hybridization.
• Pollinating the pollen grains
of one flower to the other
flower of different plants of
same species is called
artificial hybridization.
• In this method desired pollen
grains are used for
pollination.
• The stigma is protected from
contamination with other
pollen grains. It is achieved by
emasculation and bagging.
107. • Emasculation: The
removal of
anthers/stamens from
flower bud before it
matures is called
emasculation.
• Bagging: The covering of
emasculated flower with
butter paper to prevent
contamination with
other pollens is called
bagging.
108. Pollen pistil interaction
• The ability of pistil to recognize the pollen of same
species is called pollen pistil interaction.
• If wrong pollen grain (other species) is landed on
stigma, pistil rejects by preventing pollen germination.
• The acceptance and rejection is mediated by the
chemical component of pollen grain interacting with
pistil.
• Compatible pollens are encouraged by pistil for
growth and development of pollen tube.
109. Fertilization
• The fertilization in angiosperms is termed as double fertilization
and triple fusion.
• As the pollen grains matures usually contains one vegetative cell
and two generative cells.
• The vegetative cell develops into pollen tube. Generative cells
develops into male gamete.
• In some plants pollen grain sheds as two cell condition. In this,
generative cell divides into two male gamete as pollen tube forms.
110. • As the pollen
grain lands on
stigma, it starts to
germinate.
• The pollen tube
developed comes
out of germ pore.
• It grows through
the tissue of
stigma, style and
penetrates the
ovule.
111. • The entry of pollen tube in to ovule is from different place
are identified into,
1. Porogamy: It is the entry of pollen tube into ovule through
micropyle.
2. Chalazogamy: It is the entry of pollen tube into ovule
through chalaza.
3. Misogamy: It is the entry of pollen tube into ovule
through integument or funicle.
112. • As pollen tube enters the ovule, the tip
ruptures inside the embryo sac releasing two
male gametes.
113. • One of the male gamete fuses with egg and forms
diploid zygote.
• The another male gamete fuses with diploid
secondary nucleus to form triploid endosperm.
114. • The fusion of two polar nuclei (to form secondary
diploid nucleus) and male gamete to form
endosperm is termed as triple fusion.
• The two fusions as zygote formation and
endosperm formation is termed as double
fertilization.
115.
116. • Post-fertilization events.
• It is the events that takes place after double
fertilization. It includes,
1. Endosperm development.
2. Embryo development.
3. Maturation of ovule into seed.
4. Maturation of ovary into fruit.
117. Endosperm:
• The primary endosperm cell under goes repeated
mitotic cell division to form triploid endosperm tissue.
• Endosperm develops first followed by an embryo
development. Bcoz it provides nutrition to the
developing embryo.
• Three different types of endosperms are identified.
• Nuclear endosperm: In this primary endosperm cell
nucleus undergoes free nuclear division. All these
nuclei are pushed to the periphery forming central
vacuole.
• The cytokinesis results in the formation of endosperm
tissue.
• Ex: coconut. The vacuole is filled with fluid.
118. • Cellular endosperm: In this primary endosperm
cell division, karyokinesis undergoes with
cytokinesis. Ex: Datura.
• Helobial endosperm: In this primary endosperm
cell divides in to two unequal cells. One cell
undergoes cellular division and other under goes
free nuclear division. Ex : monocots.
• Functions of endosperm:
• The cells of endosperm tissue are tripled and
filed with reserve food materials. It nourish the
developing embryo.
• In pea, groundnut, beans the endosperm is
completely consumed by developing embryo.
• In some seeds like coconut, castor endosperm
persists mature seeds.
119. Embryo development:
• Embryogenesis in Dicot: The
zygote divides mitoticaly,
transversely in to two cells.
• The cell present towards
micropyle regionis called
suspensor cell.
• The cell present towards
chalazal region is called
embryonal cell .
• The suspensor cell divides
and forms 7 – 10 cells called
suspensor.
• The first cell of suspensor is
called haustorium. It enlarges
and attaches to the embryo
sac.
120. • The lower cell of
suspensor is called
hypophysis. It attaches
to embryo.
• The embryonal cell
divides into eight cells.
The four cells develops
in to plumule and two
cotyledon.
• Another four cells near
the suspensor
develops in to
hypocotyl and radicle.
121. • The fully developed embryo of dicotyledon has an
embryonal axis that differentiated into plumule,
two cotyledons and radicle.
• The lower end of radicle (root tip) is covered with
root cap.
• In the beginning embryo is globular. When two
cotyledons differentiates it forms heart shaped.
122.
123. • In monocots: The zygote divides transversely in to
suspensor cell present at micropyle region and embryonal
cell present at chalazal region.
• The embryonal cell divides into globular embryo. It forms a
massive cotyledon and plumule. Plumule covers by
coleoptile.
• The prescence of single cotyledon is called scutellum.
• At lower end of embroynal axis radicle develops. It is
covered by a sheath called coleorhiza.
124. • Seed: It is the final product of
sexual reproduction. It is the
fertilized ovule.
• Seed consists of seed coat,
cotyledon and embryonal axis.
125. • The cotyledons are swollen due to storage of reserve food.
• The seeds are albuminous or non-albuminous.
• In albuminous seed endosperm is not completely used up
by embryo. Ex: wheat, maize, castor, sunflower.
• In some seeds like black pepper the nucellus also present.
The residual persistant nucellus is called perisperm.
• In non albuminous seed endosperm is completely used up
by embryo. Ex: Pea. Ground nut.
126. • The integument of ovule develops into seed coat.
• The micropyle remains as a pore in the seed coat.
It facilitate the entry of oxygen and water in to
seed during germination.
• Seeds dry up by loosing water. The embryo enters
the stage of inactivity called dormancy. As the
favorable condition available it starts germination.
• Fruit.
• The wall of ovary develops into fruit wall called
pericarp. It surrounds the seed.
127. • In apple, strawberry the thalamus develops into
fruit wall. Hence these are called false fruit.
• The fruits developed from unfertilized ovary are
called parthenocarpic fruits. These are seedless
fruits.
128. • Apomixis: The seed developed without
fertilization of ovule is called apomixes.
• The fruits developed from unfertilized ovule are
called apomictic fruits.
• The progeny of hybrid segregate their
characters and not maintains hybrid character
generation after generation. Hence the formers
should buy hybrid seeds every year. It makes
expansive.
• The apomixes is done in hybrid plants to avoid
the segregation of characters. The formers can
use hybrid seeds to raise new crop every year.
129.
130. • Polyembryony: The presence of more than
one embryo in seed is called polyembryony.
Ex: citrus fruit seeds.
