Pollination, transfer of pollen grains from the stamens, the flower parts that produce them, to the ovule-bearing organs or to the ovules (seed precursors) themselves. In plants such as conifers and cycads, in which the ovules are exposed, the pollen is simply caught in a drop of fluid secreted by the ovule. In flowering plants, however, the ovules are contained within a hollow organ called the pistil, and the pollen is deposited on the pistil’s receptive surface, the stigma. There the pollen germinates and gives rise to a pollen tube, which grows down through the pistil toward one of the ovules in its base. In an act of double fertilization, one of the two sperm cells within the pollen tube fuses with the egg cell of the ovule, making possible the development of an embryo, and the other cell combines with the two subsidiary sexual nuclei of the ovule, which initiates formation of a reserve food tissue, the endosperm. The growing ovule then transforms itself into a seed.
Download here: http://www.agrislide.com/fertilization-plants-ppt/
This is a nice presentation on "Fertilization of plants". you can found all of the information of plant fertilization on this presentation.
Pollination, transfer of pollen grains from the stamens, the flower parts that produce them, to the ovule-bearing organs or to the ovules (seed precursors) themselves. In plants such as conifers and cycads, in which the ovules are exposed, the pollen is simply caught in a drop of fluid secreted by the ovule. In flowering plants, however, the ovules are contained within a hollow organ called the pistil, and the pollen is deposited on the pistil’s receptive surface, the stigma. There the pollen germinates and gives rise to a pollen tube, which grows down through the pistil toward one of the ovules in its base. In an act of double fertilization, one of the two sperm cells within the pollen tube fuses with the egg cell of the ovule, making possible the development of an embryo, and the other cell combines with the two subsidiary sexual nuclei of the ovule, which initiates formation of a reserve food tissue, the endosperm. The growing ovule then transforms itself into a seed.
Download here: http://www.agrislide.com/fertilization-plants-ppt/
This is a nice presentation on "Fertilization of plants". you can found all of the information of plant fertilization on this presentation.
This seeks to throw light on the process by which organisms give rise to offspring of their kind and all forms of mechanisms and structures in plants that are directly and indirectly involve in that process
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The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
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For more information, visit-www.vavaclasses.com
4. 2. Monoecious plant: male and female flowers on the
SAME tree (e.g. oak)
Male
flowers Female
flowers
(from the Greek "mono-oikos" = "a single house")
UNISEXUAL
5. 3. Dioecious plant: male and female flowers on SEPARATE
trees
Male carob
flowers
Female carob
flowers
Fruit only on
female trees
(from the Greek "di-oikos" = " two homes")
UNISEXUAL
6. Flower parts are organised in
circles called whorls
sepals
petals
stamens
carpels
11. Insect- Pollinated flowers
• Some plants take advantage of the
sex drive of certain insects…
• Certain orchids look like female
wasps, and even smell like them!
12. • Males try to mate with them, and in the
process they pollinate the plant
• The orchid gets pollinated, but the male
wasp only gets frustrated!
13. Reproductive floral organs: male
Function of:
anther: forms pollen grains
filament: hold anther
pollen grain: contains the male
gamete
19. Vertical section
through carpel
(attaches an ovule
to the ovary wall)
(the point of attachment of
ovule to ovary)
funicle
stigma
style
ovary wall
ovule
ovary
placenta
22. • The ovary may contain one or
more Ovules
• Each ovule bears one female egg
cell
• The ovule develops into a seed
OVULE
23. THE FORMATION OF POLLEN GRAINS
THE ANTHER HAS FOUR POLLEN SACS
FOUR
POLLEN
SACS
24. Vascular bundle
Pollen sac /
Anther sac
TS Anther
Pollen grain
(contains the
male gamete)
A tetrad of 4 haploid
cells – separate to
become pollen grains
25. THE FORMATION OF POLLEN GRAINS
EACH POLLEN SAC HAS HUNDREDS OF
MICROSPORE MOTHER CELLS OR POLLEN MOTHER
CELLS WHICH ARE DIPLOID CELLS
26. In the pollen sac, pollen mother cells divide by meiosis
to produce the pollen grains.
29. Production of pollen grains
HaploidHaploid
HaploidHaploid
Meiosis in anther 4
haploid daughter cells,
also called pollen tetrads
FOUR
POLLEN
SACS
30. Haploid
Haploid
HaploidHaploid
As anther matures, 4 microspores of
a tetrad separate from each other.
Production of pollen grains
Haploid nucleus of each microspore
undergoes a single mitotic division.
The 2 resulting haploid nuclei become
encased in a thick, resistant wall,
forming a pollen grain.
Pollen Grain
Mitosis
31. Pollen grain
Pollen Wall
Tube Cell
Generative Cell
Waterproofing prevents desiccation
during pollen transfer. Recognition
proteins cause allergic reactions.
cytoplasm cytoplasm
nucleus
nucleus
Digests path
through stigma,
style, and ovary.
Locates
micropyle of
ovule.
Penetrates into
embryo sac.
nucleolus
nucleolus
Divides by
mitosis to
make two
sperm.
Both join in
syngamy
events.
38. Nucleus Of The Megaspore Undergoes Three Mitotic Divisions
Mitosis
1
Mitosis
2
Mitosis
3
• 3 Migrate To One End Of The
Cell - Antipodal Cells
• 2 Nuclei Move To The Center -
Polar Nuclei
• 3 Nuclei Near The Micropyle - 1
Egg Cell Clamped By 2 Synergid
Cells
EMBRYO SAC
8 Nuclei
44. Self-pollination:
the transfer of pollen
from the anther to the
stigma of the:
same flower, or
of another flower of the
same plant
Self-pollination:
the transfer of pollen
from the anther to the
stigma of the:
same flower, or
of another flower of the
same plant
Cross-pollination:
the transfer of pollen to
a flower on a different
plant of the same
species
Cross-pollination:
the transfer of pollen to
a flower on a different
plant of the same
species
46. Plant fertilisation
• When pollen sticks
to the stigma it
absorbs water and
starts to germinate
• A pollen tube will
grow out of the grain
and through the style
towards the ovary
47. Plant fertilisation
• The pollen tube nucleus
remains close to the tip of
the tube.
• Digestive enzymes are
secreted from the tube.
• The tube is attracted by
chemicals given out by
the ovary.
48. Plant fertilisation
• As the tube grows the
generative nucleus
divides by mitosis to
form two haploid
male gametes.
Tube nucleus
Male gamete
49. Plant fertilisation
• The pollen tube enters
the ovule through the
micropyle.
• Once inside the ovule
the tube nucleus
degenerates and the male
gametes enter the
embryo sac
50.
51. Double fertilisation
• One of the male
gametes fuses with the
female gamete forming
a diploid zygote.
• The other male gamete
fuses with the 2 polar
nuclei in the centre of
the embryo sac forming
a triploid nucleus –
called the endosperm
nucleus.
52. • The union of two male gametes with different
nuclei of the embryo sac is termed double
fertilization.
– Double fertilization ensures that the endosperm will
develop only in ovules where the egg has been
fertilized.
– This prevents angiosperms from squandering
nutrients in eggs that lack an embryo.
53. Summary : Double FertilizationSummary : Double Fertilization
fusion of male gamete & female gamete to form a zygote
fusion of male gamete & 2 polar nuclei to form endosperm
Process
Pollen grain lands on a stigma and germinates
Pollen tube grows down the style & ovary - secretes enzyme to
digest a pathway through style
Generative nucleus divides – form 2 male gametes
Tube nucleus goes before male gametes & disintegrates
One male gamete fuse with egg cell – zygote
One male gamete fuses with 2 polar nuclei to form endosperm
62. OVULE INSIDE OVARYOVULE INSIDE OVARY
SEED INSEED IN
A PODA POD
TUBETUBE
NUCLEUSNUCLEUS
GENERATIVEGENERATIVE
NUCLEUSNUCLEUS
A TETRAD OF HAPLOIDA TETRAD OF HAPLOID
MICROSPORES INSIDEMICROSPORES INSIDE
POLLEN SACPOLLEN SAC