Sexual and Asexual reproduction in plants with pollination and development of gametophytes and double fertilization with embryo and endosperm formation.

1. Pollination
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POLLINATIO
N
Definition & Types
Pollination is defined as the transfer of pollen grains from the anther to the stigma of
the same flower or another flower.
The process of fertilization was first discovered by Camerarius.
Importance of pollination:
1.It is the first essential step towards sexual reproduction.
2. It leads to stimulation and germination of pollen grains to produce male gametes.
3. It helps to bring male and female gametes closer to fertilization.

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POLLINATIO
N
Definition & Types
Pollination
Cross-pollinationSelf- pollination
Autogamy Geitnogamy Xenogamy Hybridization

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POLLINATIO
N
Definition & Types
SELF POLLINATION
When the pollen gains are transferred from the anther to the stigma of the same flower or another
flower on the same mother plant, it is called self-pollination.
AUTOGAMY :
When the pollen grains are transferred from the anther to the stigma of the same flower, it is called
autogamy. It is possible only in bisexual flowers. E.g. Pea, Mirabilis, Solanum.
GEITONOGAMY :
When the pollen grains of a flower are transferred to the stigma of another flower on the same mother
plant, it is called geitonogamy. E.g. Cucurbita, Maize.
CROSS POLLINATION (Allogamy)
When the pollen gains of the flower of one plant arc transferred to the stigma of the flower on the other
plant of same or different species, it is called cross-pollination.
XENOGAMY :
When cross-pollination takes place between two plants of the same species, it is called xenogamy.
HYBRIDIZATION:
When cross-pollination takes place between two plants of different species or genera, it is called
hybridization.

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POLLINATIO
N
Merits & Demerits of Self pollination
Advantages:
- It is sure method of pollination in bisexual flowers, where the sex organs mature at the same time
- There is the least wastage of pollen gains.
- The plants do not have to spend energy on special adaptations like color, nectar, fragrance etc.
- The plants do not have to depend upon external agencies.
- Genetically, pure line varieties can be obtained.
- Once an improved variety of crop or seed or fruit is obtained an increase in the number of the -
same variety can be achieved only by self-pollination.
Disadvantages:
- It is not possible to introduce a desirable character in the progeny.
- It is not possible to eliminate undesirable characters from the progeny.
- Continuous self-pollination, generation after generation results in weak progeny.
- Self-pollination produces comparatively less number of seeds, which are of poor quality and less
viability.

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POLLINATIO
N
Merits & Demerits of Cross pollination
Advantages:
- It is possible to introduce a desirable character in the progeny.
- It is possible to eliminate undesirable characters from the progeny.
- It results in a new combination of characters.
- Thus new varieties of plants are produced which are high yielding and disease resistant.
- Production of seeds is more and they are viable.
- The offsprings are healthier and better suited for survival.
Disadvantages:
- It is possible to eliminate some desirable character in the progeny.
- There is considerable wastage of pollen grains.
- Since cross-pollination results in the formation of new genotypes, which are genetically
immune, it may also develop undesirable characters in the progeny.
- Since it depends on external carriers, failure chances are more.
- Thus, it is not an economical method since a lot of plant energy is wasted for attraction of
carriers.

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POLLINATIO
N
Agencies of Pollination
BioticAbiotic
Agencies of
pollination
Wind – Anemophily
Water - Hydrophily
Animal - Zoophily
Insects – Entemophily
Birds – Ornithophily
Bats – Chiropterophily
Snails – Malacophily
Ants – Myrmecophily
Snakes - Ophiophily

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POLLINATIO
N
Floral Adaptations of ANEMOPHILY
1. The flowers are small and inconspicuous but numerous. The anemophilous plants grow in large
groups to ensure pollination.
2. The flowers do not have bright colors, pleasant fragrance, or nectar glands.
3. When flowers are unisexual, the male flowers are more numerous compared to females and are
situated at a higher level.
4. Lower flowers of inflorescence open earlier. Pollen from upper flowers pollinates them later.
5. Essential whorls like stamen and carpels are well exposed while accessory whorls like calyx and
corolla are absent or reduced.
6. Anthers are versatile and they swing in all directions with the breeze.
7. The stigma is often branched and feathery to increase the area for reception of pollen gains.
8. Pollen grains are produced in large numbers, as there is more wastage.
9. Pollen grains are small, pale yellow, smooth and dry or may be winged (e.g. Pinus), so they can be
carried for greater distances by the wind.
10. Some wind-pollinated flowers like Urtica diocia have an explosive mechanism by which the
anthers burst and surcharge the air with pollens.
11. In plants like maize, male flowers (tassel) are at apex while female flowers (ear) are at the base to
facilitate pollination
12. Many plants are wind pollinated
Monocots : Date palm, coconut palm, many grasses, sugarcane, wheat, rice, maize, jowar
Dicots : Amaranthus, Chenopodium, Papaya, Oak, Cannabis (Bhang)

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POLLINATIO
N
Floral Adaptations of HYDROPHILY
Pollination carried out by water is described as hydrophily.
Many plants like ceratophyllum, vallisneria, hydrilla, lemna, zostera etc. exhibit this type of
pollination agent.
The adaptations shown by hydrophilous flowers are as follows:
1. The flowers are unisexual, small and inconspicuous.
2. The flowers do not have bright colors, pleasant fragrance or nectar glands.
3. Perianth (tepals) has a waxy coating and is widely open to expose essential whorls.
4. Pollen grains are produced in large numbers.
5. Pollen grains are without exine, have a waxy coating and are light in weight.
6. Specific gravity of pollen grain is controlled by one or more starch grains in the pollen grain.
7. Stigma is long and sticky and has a waxy coating.
8. Flowers are usually unisexual and open under water or at the surface of water. Swaying
movements of the plants help in pollination.
Depending on whether the plants are totally or partially submerged, 2 types of hydrophily have been
noticed:
A) EPI-HYDROPHILY
B) HYPO-HYDROPHILY

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POLLINATIO
N
Floral Adaptations of
HYPOHYDRODROPHILY
HYPOHYDROPHILY :
1. Pollination with the help of water takes place below the surface of the water.
2. It is seen in totally submerged marine plants (hydrophytes) like Ceratophyllum.
3. The plant is bisexual, but individual flowers are unisexual. The male flower contains 30 - 40
stamens.
4. At maturity, the anthers get separated, at the base and float to the surface of the water, where
they dehisce (undergo anthesis) and liberate the pollen gains.
5. The pollen grains bear the specific gravity as that of water and the released pollen gains float and
then geminate after which they pollinate the swaying female flower.
6.In plants like Zoster marina, pollens grains are exceptionally long and needle like and resemble a
pollen tube.

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POLLINATIO
N
Pollination in Vallisneria
EPIHYDROPHILY :
1. Pollination takes place on the surface of the
water. It is the more common type of hydrophily.
2. It is seen in partially submerged plants like
Vallisneria, whichis dioecious (unisexual) and bears
flowers under water on different male and female
plants.
3. The male flowers get detached at maturity from
the parent plant and float on the surface of water.
4. At the time of pollination the female flowers are
bought to the surface of the water with help of a
long slender pedicel (stalk) where it gets arranged
in a horizontal position. It creates a cup shaped
depression around it due to its weight.
5. Two stamens in the flower are exposed.
6. Some of the male flowers floating on the water
surface are pulled towards the cup shaped
depression of the female flower.
7. The anthers come in contact with the exposed
stigma to transfer pollen grains.
8. The stalk of the female flower after pollination
undergoes spiral twisting and ultimately brings the
pollinated female flowers back under the surface
of water, where the fruit is formed.

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POLLINATIO
N
Floral Adaptations of ENTEMOPHILY
ENTOMOPHILY:
- Pollination carried out through insects is called entomophily.
- The common insects, which help in pollination : Bees ,Flies, Wasps, Moths, and Beetles etc.
-The common examples of insect pollinated flowers are Jasmine, Bougainvillea, Sunflower, Cestrum
(Raat-Rani), Amorphophallus, Calotropis, etc.
ADAPTATIONS :
1. The flowers are brightly colored and produce a pleasant fragrance.
2. The flowers are provided with nectar glands, which secrete nectar that is rich in glucose, fructose,
and sucrose. Insects visit flowers in search of nectar.
3. In plants like Viola (Pansy), guide markings on petals are present to guide the insects to the
nectaries.
4. The accessory whorls i.e. Calyx and Corolla are well developed to conceal and protect the essential
whorls i.e. Stamens and Carpels.
5. Since there is no wastage of pollen grains, pollen grains produced are comparatively less in number.
6. The pollen gains are spiny to adhere to the bodies of the visiting insects.
7. The stigma is short, rough and sticky to receive the pollen grain.
8. Some flowers like Arum, Rafflesia emits an extremely unpleasant and foul odor to attract flies to
bring about pollination.
9. In plants like Papaver, Rosa, Clematis etc. edible pollen grains rich in proteins and lipids are
produced. Some pollen grains stick to the body of insects while they feed on these edible pollen grains.

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POLLINATIO
N
Examples of ENTEMOPHILY
- The hairy wasp pollinates the Orchid, Ophyrus speculum. This orchid flower possesses an
appearance and odor similar to that of a female wasp. Thus, the male wasps mistake the ophyrus
flowers for their female counter part, land upon them and perform pseudo-copulation. They repeat
this act by visiting different flowers and thus bring about pollination.
- Flowers like Helianthus, Salvia etc. are white but have a pleasant fragrance because moths, which
are nocturnal in nature, pollinate them. (Color not required)
- In the Yucca plant, a moth called Yucca-moth bores a hole in the ovary of yucca flower and lays its
eggs in it. Then the moth collects pollen from several flowers and pushes the pollen down the
stigma. Fertilization takes place and seeds develop, and the moth larvae feed on the developing
seeds. The plant to propagate the species uses the seeds, which remain unconsumed. Thus, the
Yucca plant and the moth are co-dependent on each other for their existence

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POLLINATIO
N
Pollination in Salvia
The flower of Salvia has 2 stamens. The two anther lobes are widely separated by a prolonged, curved
connective, which allows the 2 stamens to swing like a lever mechanism :
-The upper lobe is fertile, while the lower lobe is sterile. In natural conditions, the connective remains
upright. When an insect enters the corolla tube, it pushes the lower lobe in such a way that the upper
fertile lobe swings and touches the back of the insect and deposits pollen gains there.
-The flower is protandrous (i.e. androecium matures before gynoecium). When the same insect visits
the flower, when the gynoecium has matured, the bent stigma touches the back of the insect and
receives the pollen grain.

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POLLINATIO
N
Floral Adaptations of ORNITHOPHILY
Pollination carried out by birds is described as ornithophily.
The common examples of ornithophilous flowers are :
Sterilitzia reginae (by Sun-birds), Salmalia and Erythrina i.e. Coral tree (by Crows and Mynas),
Bignonia, Sanchezia, Bombax i.e. Silk cotton tree, Callistemon i.e. Bottle brush, Butea
monosperma etc.
The common birds, which help in pollination, are Humming birds, Sun birds, Honey suckers etc
1. The flowers are large, showy and brightly colored with colors
like Red, Orange, and Yellow. These can attract birds from long
distances. (Only Honeybees can visualize colors like Pure Blue,
Parrot Green etc.)
2. The flowers are generally tubular (Nicotianagluca) or cup
shaped (Callistemon).
They are scentless (without fragrance).
3. The stamens and carpels protrude from beneath the perianth
lobes.
4. The flowers produce copious amounts of mucilagenous nectar,
which is rich in sugars and is more important birds as a drink rather
than food.
5. A humming bird can consume up to half its body weight of
nectar in a single day.
6. The flowers produce large amounts of sticky pollen grains,
which adhere to the body of the birds, while they are feeding on
nectar

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POLLINATIO
N
Floral Adaptations of CHIROPTEROPHILY
CHIROPTEROPHILY:
Pollination carried out by bats is descried as
chiropterophily.
The common examples of chiropterophilous flowers
are
durio, kigella pinnata, anthocephalus (kadamb),
adansonia (baobab tree), bauhinia etc.
The common adaptations of chiropterophilous flowers
are:
1. The flowers are freely exposed, large and tough so that
bats can hold on to them.
2. The flowers open in the evening since bats are
nocturnal animals
3. The flowers give off a strong scent like that of rotting
fruits to attract bats.
4. Bats feed on nectar and pollen produced in very large
amounts by these flowers.
Flowers of adansonia have 1500-2000 stamens to produce
large number of pollen grains.
Bats can transport pollen to distances as large as 30 km.

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POLLINATIO
N
Contrivances of Pollination
Contrivances
Cross-pollinationSelf- pollination
1. Bisexuality and Homogamy
2. Cleistogamy
1. Unisexuality
2. Dichogamy
3. Heterostyly
4. Herkogamy
5. Self-sterility

18. Male
Gametophyte

19. Development & Structure of Male Gametophyte
1. Structure of Anther
2. T.S. of Anther
3. Structure of Pollen grain
4. Development of male gametophyte

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Male gametophyte Structure of Anther
Stamen (Microsporophyll)
Anther
Anther lobes (1 lobe : Monothecous
2 lobes : Dithecous)
Pollen Sac (Microsporangia)
Pollen Mother Cells (2n)
Pollen grains (n)
Male gametes (n)

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Male gametophyte T.S. of Anther

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Male gametophyte T.S. of Anther
Anther wall Pollen sac
Anther
Epidermis Endothecium Middle layers Tapetum

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Male gametophyte Anther Wall
EPIDERMIS:
- outermost common wall layer , flattened cells , protective in function.
ENDOTHECIUM:
-internal to the epidermis, consists of single layer of cells.
-characteristic fibrous thickenings of callose.
-Fibrous thickenings (callose) and hygroscopic nature of endothecium cells help in the
dehiscence of anther at maturity.
MIDDLE LAYERS:
-Internal to the endothecium, 1 to 3 layers of parenchyma cells are present
surrounding each pollen sac or microsporangium.
- The cells of these layers degenerate at maturity
TAPETUM:
-innermost wall layer surrounding the sporogenous tissue of microsporangium.
-Cells are larger in size, dense cytoplasm and one or more diploid or a polyploidy nucleus.
-provides nourishment to the developing microspores and to sporogenous tissue.
-contributes in the formation of sporopollenin (Ubisch granules) a component of pollen
exine
-Secretes pollen kit in entemophilous pollens, hormone IAA and enzyme callase.

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Male gametophyte Pollen Sac
POLLEN SACS (microsporangium):
-The pollen sacs enclose primary sporogenous tissue, which divides and re-divides
mitotically for several generations to form a compact mass of diploid sporogenous tissue.
-The last generation of this sporogenous tissue forms microspore mother cells(diploid
pollen mother cells).
-Each pollen mother cell (2n) undergoes meiosis to produce four haploid (n) pollen grains
or microspores
-This process is called microsporogenesis.
-The four pollen grains are enclosed in a common wall showing a tetrahedral tetrad
condition.
-Pollen grains are stored in the pollen sacs.

25. - Spherical or oval haploid structures situated in the pollen sacs of the anthers.
- Each pollen grain has two walls (i.e. the double layered wall called sporoderm).
- The outer, thick and rough wall is called as exine
- The inner, thin and smooth wall is called as intine.
EXINE:
- The exine is thick due to the deposition of cutin called sporopollenin, which is resistant to chemical
and biological decomposition.
- The exine shows one or more pits (pores) called as germ pores.
- In insect pollinated pollen grains, a yellowish, sticky substance called pollen kit covers the exine.
- The exine is spiny (in insect pollinated plants) and smooth (in wind pollinated plants)
INTINE:
- It is the inner layer of sporoderm.
- It is composed of cellulose and pectin.
- It encloses protoplasm with single haploid nucleus.
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Male gametophyte Structure of Pollen grain

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Male gametophyte
Development of Male Gametophyte
Pre-pollination
(in the anther)
Post-pollination
(on the stigma)

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Male gametophyte
Pre-pollination:
-pollen grain is the initial cell of male gametophyte.
-endosporic development
-Unicellular, uninucleate pollen divides by mitosis to form 2 unequal cells
-The larger cell is called as vegetative or tube cell, which has a tube nucleus. It has a large vacuole,
cytoplasm, and nucleus and reserve food.
-The smaller one is called as the generative cell, which has a generative nucleus. It has a large nucleus,
thin cytoplasm and it lacks reserve food and vacuole. Generative cell lacks a definite cell wall and is
freely suspended in cytoplasm of vegetative cell.
-This is the 2-nucleated stage. But the cell wall between the two cells is not well formed.
Post-pollination:
-The stigma secretes a sugary solution in which the pollen grain is germinated.
-Due to this the volume of cytoplasm increases and creates a pressure, which acts on the intine.
-The intine of pollen grain comes out of the germ pore in the form of a tube called pollen tube.
-The inner covering called as intine of the pollen grain produces a pollen tube, which comes out through
a germ pore.
-The pollen tube grows down towards ovule through the style due to chemical stimulus.
-The tube nucleus enters the pollen tube first followed by the generative nucleus.
-Generative nucleus divides by mitosis to produce two haploid, non-motile, male gametes. Thus a 3-
nucleated stage is formed.
-The pollen tube along with its cytoplasm and two male gametes with the degenerating sterile
vegetative nucleus is called as the male gametophyte. Thus it is highly reduced structure.

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Male gametophyte

29. Female
Gametophyte

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Female gametophyte
1. Structure of carpel
2. V.S. of Ovule
3. Development of female gametophyte

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Female gametophyte Structure of Carpel
Carpel (Megasporophyll)
Ovary
Ovule (Megasporangium)
Megaspore Mother Cells (2n)
Female Gametophyte
Female gametes (n)
Style Stigma

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Female gametophyte V.S. of Ovule

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Female gametophyte Types of Ovule

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Ovule
Funicle Body
- Stalk of the ovule
- Supports the ovule
- Att. the ovule to placenta
1. Nucellus : mass of 2n parenchymatous cells
2. Integuments : protective coverings of the nucellus
3. Micropyle : opening left by the integuments
4. Chalaza : point opp micropyle from where the
integuments arise
5. Hilum : point of att of funicle to the body.
6. Embryo sac : 7 celled / 8 nucleated
a) Antipodals : 3 cells towards the chalaza
b) Egg Apparatus : 3 cells towards the micropyle
( 2 lateral synergids and
1 central egg cell )
c) Sec Nucleus : central bi-nucleated cell
Female gametophyte Structure of Ovule

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Female gametophyte Structure of Ovule
Structure Function
1. Funicle Stalk of the ovule. Att the ovule to the placenta
2. Nucellus 1 of the cells develops as Megaspore mother cell
3. Integuments Protective in function and after fertilization develops as seed coat
4. Micropyle Allows the entry of pollen tube.
5. Chalaza The integuments arise fron this point
6. Hilum Att the funicle to the chalaza
7. Synergids Supply moisture to the tip of pollen tube and helps it to burst open.
8. Antipodals Nutritive and later on degenerate.
9. Egg cell Fuses with the male gamete to form the zygote
10. Sec Nucleus Fuses with the male gamete to from the TPEN.

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Female gametophyte Dev. Of Female Gametophyte

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Female gametophyte Dev. Of Female Gametophyte

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Female gametophyte Female Gametophyte

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Female gametophyte Dev. Of Female Gametophyte
DEVELOPMENT OF FEMALE GAMETOPHYTE OR EMBRYO SAC:
-One of these cells enlarges to form a megaspore mother cell.
-It undergoes meiotic division to produce four haploid cells called megaspores, which are arranged, in a
linear fashion (linear tetrad).
-The upper three degenerate.
-The lowermost one increases in size to form the embryo sac or female gametophyte.
-The nucleus within the sac divides thrice by mitosis to form eight nuclei.
-Four of them are present at the micropylar end and four are at the chalazal end.
-One nucleus from each end then moves towards the center.
-They unite to form the secondary nucleus.
-The three nuclei at the micropylar end are together termed as egg apparatus.
-The three nuclei at the chalazal end are the antipodals.
-Of the egg apparatus, the middle one is the egg cell or the female gamete while the other two flanked
on the sides are synergids or helpers.
-As the development of the female gametophyte is within the megaspore, it is endosporic.
-As only one megaspore out of four takes part in the development of the female gametophyte (embryo-
sac), it is called monosporic. (In some angiosperms, embryo-sac may be bisporic or tetra-sporic).
Generally, the embryo-sac is monosporic, endosporic, 7 celled and 8 nucleated. This is called Polygonum
type.

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Double Fertilization
Step 1:
-During fertilization, the pollen tube passes through the style and enters the ovule through the
micropyle.
-It penetrates the nucellus and enters the embryo sac.
-The synergids provide moisture to the pollen tube due to which the tip of the pollen tube bursts open.
-The male gametes are released in the embryo sac.
-The synergids now direct one male gamete to the egg cell and another male gamete to the secondary
nucleus.
-The synergids later on degenerate.

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Double Fertilization
Step 2:
-One male gamete unites with the egg cell to form the diploid zygote.
-This is called as syngamy or first fertilization.
-The second male gamete unites with the diploid secondary nucleus to form a triploid, Primary
Endospermic Nucleus (PEN). This is called as triple fusion or second fertilization.
-The syngamy and triple fusion together are called as double fertilization.
Step3:
-The male gametes are carried by the pollen tube; hence the fertilization is called as siphonogamy.
-The pollen tube enters the micropyle; hence the fertilization is called as porogamy. Sometimes the
pollen tube enters through the integuments (mesogamy) or through the base (chalazogamy)

42. Significance of double fertilization:
-After fertilization, zygote forms the embryo, which later on develops into a new plant.
-It restores the diploid condition by the fusion of haploid male and female gametes to form the zygote.
-It leads to the formation of the fruit and seeds.
-The primary endosperm nucleus (PEN) divides and re-divides to form the nutritive tissue called the
endosperm, which provides nourishment to the developing embryo. The triploid endosperm gives better
nourishment to the developing embryo in Angiosperms, while gymnospermic angiosperms are haploid.
Hence angiospermic seeds have a better viability.
-It is the characteristic of angiosperms, in which two male gametes take part in fertilization unlike
cryptogams like fern.
-Fertilization brings about a recombination of characters, resulting in variations in the offsprings.
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Double Fertilization

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Post-Fertilization Development of Embryo
1. The fertilized zygote develops a wall
around itself to form an oospore.
2. The oospore soon divides to form two
namely the basal cell and the terminal
cell.
3. The basal cell lies towards the
micropylar end, while the terminal cell
lies towards the center.
4. The basal cell divides transversely
while the terminal cell divides vertically
to form the four celled '⊥' shaped pro-
embryo.
5. The two basal cells divide transversely
to form 7 to l0-celledsuspensor.
6. The uppermost cell of the suspensor
towards the micropylar end forms the
haustorial cell while the lowermost cell
of the suspensor towards the terminal
cell is called the hypophysis.

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Post-Fertilization Development of Embryo
7. The haustorial cell enlarges in size and
attaches the suspensor to the tip of the
embryo sac. It helps to push the embryo
towards the nutritive tissue called
endosperm, which provides nutrition to
the growing embryo. The hypophysis
gives rise to the embryonic root and root
cap.
8. The two terminal cells divide at right
angles to the first one to form a 4-celled
embryo (quadrant). Each of the four cells
now divides transversely to form 8-celled
embryo (octant).
9. The eight cells are arranged in two
tiers of four cells each. The lower tier of 4
cells gives rise to the plumule and
cotyledons, while the upper tier of 4 cells
near the suspensor gives rise to the
hypocotyl.
.

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Post-Fertilization Development of Embryo
Embryo
Basal Cell/ Suspensor cell Terminal cell/Embryo cell
7 – 10 celled
Suspensor
Pushes the embryo
Towards endosperm
Quadrant
Octant
Epibasal
(Terminal)
Hypobasal
(near suspensor)
1. Plumule
2. Cotyledons
1. Hypocotyl
2. Radicle

46. Post-Fertilization Development of Endosperm
NUCLEAR ENDOSPERM:
-This is the most common type of endosperm development.
-Here, the PEN divides mitotically by free nuclear division to form 2 endospermic nuclei.
-Here, karyokinesis (i.e. division of nuclei) is not followed by cytokinesis (i.e. division of cytoplasm). There is
no wall formation.
-Both the nuclei remain in the common cytoplasm of the central cell of the embryo sac.
-This is followed by free nuclear mitosis in these 2 nuclei.
-As the division progresses, nuclei are pushed towards the periphery and a large central vacuole is created.
-Cytokinesis and wall formation then begins after a delay and proceeds from the periphery towards the
center.
-Thus, the nuclear endosperm is eventually converted into a cellular endosperm
-Nuclear type of endosperm is also commonly seen in maize, wheat, rice, sunflower etc
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47. Post-Fertilization Development of Endosperm
CELLULAR TYPE:
-Here, the first mitotic division in primary endosperm nucleus (karyokinesis) is immediately followed
by cytokinesis and wall formation.
-Each successive mitosis in the daughter cells is accompanied by formation in the same pattern.
-Thus, the developing endosperm is cellular right from the beginning.
-It is seen in dicots like Gametopetalae i.e. Datura, Adoxa, Petunia etc.
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48. Post-Fertilization Development of Endosperm
HELOBIAL TYPE:
-It is an intermediate type between the nuclear and cellular types of endosperm.
-The first mitotic division in primary endosperm nucleus is accompanied by cytokinesis and wall
formation (cellular type), but the subsequent nuclear divisions are free nuclear (nuclear type).
-The nuclear divisions are more at the micropylar end, than the chalazal end.
-It is seen in monocots of the order Helobieae like Vallisneria, Limnophyton etc.
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NON-ENDOSPERMIC SEED:
-In seeds like gram, bean and pea, the endosperm is
completely absorbed by the developing embryo.
-As a result, the seed does not contain endosperm.
-The cotyledons become fleshy and thick- due to the
storage of food.
-Such seeds are called exalbuminous or non-
endospermic seeds
Post-Fertilization Types of seeds
ENDOSPERMIC SEED:
-In seeds of castor, sunflower, coconut and cereals
like wheat, maize, the endosperm is not completely
absorbed by the developing embryo.
-Such seeds are called as albuminous or
endospermic seeds.
-The cotyledons are thin and papery.

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Post-Fertilization Importance of seeds
Dormancy:
-temporary suspension of growth.
-presence of certain growth inhibitors in the seeds, which prevent germination.
-During this period, seeds are dispersed at different places.
Viability:
-It is the functional ability of seeds to germinate after considerable dormancy period.
-Germination can be delayed till the onset of favorable conditions.
Reserve food:
-Fully developed embryo is nourished by food stored in either endosperm or in the cotyledons
during germination of seed and a seedling is produced
Protective coat:
-Testa, the outer, hard coat, gives protection against the mechanical fluctuations in temperature and dry
conditions.
-Animals eat fruits and either throw away seeds if they are consumed, they are not digested due to hard seed
coat and are removed through excreta.
Dispersal:
-Some seeds produce various structures like wings, pappus calyx (persistent and hairy), hooks or
sticky substances, and seeds actively or passively transported to distant places.
Edible fruits:
-Many fruits are consumed different organisms and seeds are thrown.
Apart from the above reasons seeds are important due to :
a)Dependable method of reproduction b) Perennation c) Dispersal
d) Variation e) Agriculture

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Apomixis & Polyembryony
- Seeds are the products of fertilization.
- In some species of family Asteraceae and some grasses, seeds are produced without
fertilization. This is called apomixis and such seeds are called apomictic seeds.
- Apomixis is a form of asexual reproduction that mimics sexual reproduction.
- In some species, diploid egg cell is formed without reduction division (meiosis) and it
develops into an embryo without fertilization and thus apomictic seeds can be formed.
- In many Citrus varieties, some of the nucellar cells near the embryo sac start dividing,
protrude into the embryo sac and develop into the embryos. Ovule in such species
contains many embryos, and this is called polyembryony.

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Apomixis
Apomixis
Recurrent Apomixis Non- recurrent apomixisAdventive Embryony
A diploid embryo is formed
from the diploid egg cell or
from some other diploid cell
of the embryo sac
e.g. Parthenium. Rubus.
The MMC undergoes the
usual meitoic division and
haploid embryo sac is
formed
e.g.Solanium, Lilium
When embryos arise directly
from nucellus or integument
e.g. Citrus, opuntia
) Diplospory : Embryo develops
rom Diploid MMC
b) Apospory : Embryo develops
from diplod nucellelar cell
a) Haploid parthenogenesis :
Embryo arises from haploid egg
cell
b) Haploid Apogamy :
- Embryo arises from some other
haploid cell of embryo sac
-Plants produced are haploid and
sterile

53. Polyembryony
- The phenomenon of having more than one embryo is called as polyembryony
- Poly embryony due to fertilization of more than one egg is simple polyembryony
- Formation of extra embryos from the sporophytic tissue is called adventive
polyembryony
- Polyembryony is practically important because genetically uniform parental seedlings
are obtained from nucellar embryos.
- Nucellar embryos are superior to those obtained from vegetative propgation because
nucellar embryo seedlings are disease free and maintain their superiority for a long
time.
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54. Asexual Reproduction
- In this method, a single individual (parent) is capable of producing offspring.
- As a result, the offspring that are produced are not only identical to one another but are
also exact copies of their parent
- The term clone is used to describe such morphologically and genetically similar
individuals.
- Asexual reproduction is more common than sexual reproduction in lower organisms.
- Asexual reproduction is common among single-celled organisms, and in plants and
animals with relatively simple organizations.
Asexual Reproduction
Cell Division Special structures
1. Binary Fission : Amoeba, paramoecium
2. Budding : Yeast
1. Zoospores : Chlamydomonas (motile spores)
2. Conidia : Penicillium (non-motile spores)
3. Fragmentation : Spirogyra
4. Gemmule : sponges

55. Vegetative propogation
- The reproduction, which occurs without involving meiosis and fusion of
gametes, is called asexual reproduction.
- In Angiosperms, it occurs through the parts of vegetative organs like root,
stem, leaf or buds of a plant, therefore, it is called vegetative propagation or
vegetative reproduction.
- These vegetative parts, which act as propagules have adequate, reserve food
material and at least a growing point.
- The propagule grows to form an independent plant under favorable conditions.

56. Natural Methods of vegetative propagationVegetative propogation
A) TUBEROUS ROOTS
- Underground roots store plenty of reserve food and become swollen.
Such swollen roots are called tuberous roots.
- These roots in some plants have adventitious buds on their surface,
which sprout under favorable conditions to produce 'Leafy shoots'
(slips) and adventitious roots from the base of shoot
- Under natural conditions, 'slips' are separated after degeneration of
intervening root part
Tuberous roots
(Fleshy)
Single (Simple) e.g. Sweet Potato
Cluster (fasciculated) e.g. Asparagus, Dahlia
Non- fleshy roots Guava, Dalbergia (shisham), Albizzia,
Murraya (kadhipatta) etc

57. Natural Methods of vegetative propagationVegetative propogation
B) STEM TUBER
- In Potato plant (Solanum tuberosum), the basal
and underground part of stem produce axillary or
extra axillary underground branches.
- The terminal part of such branches becomes
swollen due to storage of starchy reserve food.
- These swollen tips of underground branches of
stem are called stem tubers.
- A stem tuber has many notches on its surface
called 'eyes'.
- Each 'eye' is actually at a node and consists of one
or more small axillary buds and reduced scale
leaves.
- After termination of dormancy period, under
favorable conditions, one of axillary bud from an
“eye” sprouts by suppressing the growth of other
buds.
- The tuber is cut into pieces, each at least with one
“eye”, and is grown separately for commercial
cultivation.

58. Natural Methods of vegetative propagationVegetative propogation
C) RUNNER
- Runner is a slender, prostrate, sub aerial branch, which creeps horizontally on the
soil.
- It is produced by the plants like Cynodon (doobgrass), Fragaria (strawberry) and
Oxalis etc. for vegetative propagation.
- Runner develops from the lower axillary bud of stem and is a thin, elongated,
cylindrical, wire like structure with long internodes.
- It creeps on the ground and becomes rooted at the nodes.
- Shoots are produced from upper side of nodes.
- After getting detached from parent, such shoots grow as independent plants.
- A parent plant produces many such runners, which spread in all the directions.

59. Natural Methods of vegetative propagationVegetative propogation
C) LEAF
- In plants like Bryophyllum, Kalanchoe, Begonia etc.,
vegetative propagation takes place with the help of
their leaves.
- In Bryophyllum, leaf is succulent with crenate or
notched margin.
- Adventitious buds called epiphyllous buds (or foliar
buds) are produced at the notches at the tip of
lateral veins.
- These buds start sprouting on the leaf to form leafy
shoot and adventitious roots.
- When such sprouts fall on the wet soil, they develop
into independent plants.
- In some species of Bryophyllum, the new plants are
formed from the leaves only when the leaf is
separated from the parent plant and falls on wet
soil.
- In Begonia, the foliar buds are produced on the
surface of leaf.

60. Artificial Methods of vegetative propagationVegetative propogation
Cuttings:
They are the small pieces of the plant parts like root, stem or leaves, which are able to develop into new plants when
placed in moist soil.
A cutting must have the primary meristem.
Cutting is the most convenient and a cheap method of propagation.
Grafting:
It is the technique of joining together the parts of two different plants in such a way that they unite and continue
their growth as one plant.
In grafting, the plant rooted in the soil and on which the part of other plant is inserted, is known as stock while the
other which is inserted on stock is called scion (graft).
Budding:
It is basically a kind of grafting in which the single bud with a small part of bark and living tissue is grafted on the
particular stock.
In grafting, the cambium plays important role.
The cambia of both, stock and scionfuse together and make the union of these two plants successful.
As monocots do not have inter or intra-fascicular cambium and do not show secondary growth, grafting is not possible
in monocots.
Micropropagation:
To produce large number of plant propagules, tissue culture technique is used.
For this shoot apical meristem is used as an explant and many shoot apices can be produced which are called
micropropagules.
These micropropagules are used to produce large number of genetically identical plants i.e. clones within short time
period.
This is called Micropropagation.