Table of Contents

Table of Contents...................................................................................................1
POLLINATION: INTRODUCTION..............................................................................2
PROCESS OF POLLINATION.....................................................................................3
TYPES OF POLLINATION.........................................................................................6
On the Basis of Pollen Source.............................................................................6
Self-Pollination................................................................................................6
Cross Pollination..............................................................................................6
On the Basis of Pollinating Agent........................................................................6
Abiotic Pollination............................................................................................6
Biotic Pollination..............................................................................................8
MECHANISM........................................................................................................10
Modes of Cross Pollination:..............................................................................10
(1) Anemophily:.............................................................................................11
(2) Hydrophily:...............................................................................................11
(3) Entomophily:............................................................................................12
(4) Ornithophily:............................................................................................12
(5) Chiropteriphily:.........................................................................................12
(6) Malcophily:...............................................................................................13
Mechanism of Self Pollination..........................................................................13
Cleistogamy...................................................................................................13
POLLEN VECTORS.................................................................................................14
Observation..........................................................................................................17
CONCLUSIONS......................................................................................................19
BIBLOGRAPHY......................................................................................................21

Page 1 of 19
 INTRODUCTION
 Pollination is the process by which pollen is transferred to the female
reproductive organs of a plant, thereby enabling fertilization to take
place.
 Like all living organisms, seed plants have a single major purpose: to
pass their genetic information on to the next generation.
 The reproductive unit is the seed, and pollination is an essential step
in the production of seeds in all spermatophytes (seed plants).
 For the process of pollination to be successful, a pollen grain
produced by the anther, the male part of a flower, must be
transferred to a stigma, the female part of the flower, of a plant of
the same species.
 The process is rather different in angiosperms (flowering plants)
from what it is in gymnosperms (other seed plants).
 In angiosperms, after the pollen grain has landed on the stigma, it
creates a pollen tube which grows down the style until it reaches the
ovary. Sperm cells from the pollen grain then move along the pollen
tube enter the egg cell through the micropyle and fertilize it,
resulting in the production of a seed.
 A successful angiosperm pollen grain (gametophyte) containing the
male gamete is transported to the stigma, where it germinates and
its pollen tube grows down the style to the ovary. Its two gametes
travel down the tube to where the gametophyte(s) containing the
female gametes are held within the carpel. One nucleus fuses with
the polar bodies to produce the endosperm tissues, and the other
with the ovule to produce the embryo, Hence the term: "double
fertilization".

Page 2 of 19
 PROCESS OF POLLINATION
 Pollen germination has three stages; hydration, activation and pollen
tube emergence. The pollen grain is severely dehydrated so that its
mass is reduced enabling it to be more easily transported from
flower to flower.
 Germination only takes place after rehydration, ensuring that
premature germination does not take place in the anther. Hydration
allows the plasma membrane of the pollen grain to reform into its
normal bilayer organization providing an effective osmotic
membrane.
 Activation involves the development of actin filaments throughout
the cytoplasm of the cell, which eventually become concentrated at
the point from which the pollen tube will emerge. Hydration and
activation continue as the pollen tube begins to grow.
 In conifers, the reproductive structures are borne on cones. The
cones are either pollen cones (male) or ovulate cones (female), but
some species are monoecious and others dioecious.
 A pollen cone contains hundreds of microsporangia carried on (or
borne on) reproductive structures called sporophylls. Spore mother
cells in the microsporangia divide by meiosis to form haploid
microspores that develop further by two mitotic divisions into
immature male gametophytes (pollen grains).
 The four resulting cells consist of a large tube cell that forms the
pollen tube, a generative cell that will produce two sperm by mitosis,
and two prothallial cells that degenerate.
 These cells comprise a very reduced microgametophyte, that is
contained within the resistant wall of the pollen grain.

Page 3 of 19
 The pollen grains are dispersed by the wind to the female, ovulate
cone that is made up of many overlapping scales (sporophylls, and
thus megasporophylls), each protecting two ovules, each of which
consists of a megasporangium (the nucellus) wrapped in two layers
of tissue, the integument and the cupule, that were derived from
highly modified branches of ancestral gymnosperms.
 When a pollen grain lands close enough to the tip of an ovule, it is
drawn in through the micropyle ( a pore in the integuments covering
the tip of the ovule) often by means of a drop of liquid known as a
pollination drop.
 The pollen enters a pollen chamber close to the nucellus, and there
it may wait for a year before it germinates and forms a pollen tube
that grows through the wall of the megasporangium (=nucellus)
Page 4 of 19
 where fertilization takes place. During this time, the megaspore
mother cell divides by meiosis to form four haploid cells, three of
which degenerate.
 The surviving one develops as a megaspore and divides repeatedly to
form an immature female gametophyte (egg sac). Two or three
archegonia containing an egg then develop inside the gametophyte.
 Meanwhile, in the spring of the second year two sperm cells are
produced by mitosis of the body cell of the male gametophyte.
 The pollen tube elongates and pierces and grows through the
megasporangium wall and delivers the sperm cells to the female
gametophyte inside.
 Fertilization takes place when the nucleus of one of the sperm cells
enters the egg cell in the mega gametophyte’ sarchegonium.
 In flowering plants, the anthers of the flower produce microspores
by meiosis. These undergo mitosis to form male gametophytes, each
of which contains two haploid cells.
 Meanwhile, the ovules produce megaspores by meiosis, further
division of these form the female gametophytes, which are very
strongly reduced, each consisting only of a few cells, one of which is
the egg. When a pollen grain adheres to the stigma of a carpel it
germinates, developing a pollen tube that grows through the tissues
of the style, entering the ovule through the micropyle.
 When the tube reaches the egg sac, two sperm cells pass through it
into the female gametophyte and fertilization takes place.

Page 5 of 19
 TYPES OF POLLINATION

On the Basis of Pollen Source

 Depending on the source of pollen, pollination can be classified into
2 types –
o Self-pollination
o Cross Pollination (Xenogamy)

Self-Pollination
 Self-Pollination is the type of Pollination in which pollen grains are
transferred from anther to the stigma of the same flower
(Autogamy) or pollen grains are transferred from anther to the
stigma of different flower of the same plant (Geitonogamy).

Cross Pollination
 Cross Pollination or Xenogamy is the type of pollination in which
pollen grains are transferred from anther to the stigma of a different
plant.

On the Basis of Pollinating Agent

 Depending on agent of Pollination, pollination can be classified into
abiotic pollination and biotic pollination

Abiotic Pollination
• Abiotic pollination refers to situations where pollination is mediated
without the involvement of other organisms.
• The most common form of abiotic pollination, anemophily, is
pollination by wind. Wind pollination is very imprecise, with a
minute proportion of pollen grains landing by chance on a suitable
receptive stigma, the rest being wasted in the environment.

Page 6 of 19
• This form of pollination is used by grasses, most conifers, and many
deciduous trees. Hydrophily is pollination by water, and occurs in
aquatic plants which release their pollen directly into the
surrounding water.
• About 80% of all plant pollination is biotic. In gymnosperms, biotic
pollination is generally incidental when it occurs, though some
gymnosperms and their pollinators are mutually adapted for
pollination.
• The best-known examples probably are members of the order
Cycadales and associated species of beetles.
• Of the abiotically pollinated species of plant, 98% are anemophilous
and 2% hygrophilous, their pollen being transported by water.
• It is thought that among angiosperms, entomophily is the primitive
state; this is indicated by the vestigial nectarines in the wind-
pollinated Utica and other plants, and the presence of fragrances in
some of these plants.
• Of the angiosperms, grasses, sedges, rushes and catkin-bearing
plants are in general wind pollinated. Other flowering plants are
mostly biotic, the pollen being carried by animal vectors.
• However, a number of plants in multiple families have secondarily
adopted wind pollination in contrast to other members of their
groups. Some plants are intermediate between the two pollination
methods.
• Common heather is regularly pollinated by insects, but produce
clouds of pollen and some wind pollination is inevitable, and the
hoary plantain is primarily wind pollinated, but is also visited by
insects which pollinate it.

Page 7 of 19
Biotic Pollination
• More commonly, the process of pollination requires pollinators:
organisms that carry or move the pollen grains from the anther of
one flower to the receptive part of the carpel or pistil (stigma) of
another. This is biotic pollination.
• The various flower traits (and combinations thereof) that
differentially attract one type of pollinator or another are known as
pollination syndromes.
• At least 100,000 species of animal, and possibly as many as 200,000,
act as pollinators of the estimated 250,000 species of flowering
plants in the world.
• The majority of these pollinators are insects, but about 1,500 species
of birds and mammals have been reported to visit flowers and may
transfer pollen between them.
• Besides birds and bats which are the most frequent visitors, these
include monkeys, lemurs, squirrels, rodents and possums.
• Entomophily, pollination by insects, often occurs on plants that have
developed colored petals and a strong scent to attract insects such
as, bees, wasps and occasionally ants (Hymenoptera), beetles
(Coleoptera), moths and butterflies (Lepidoptera), and flies (Diptera).

Page 8 of 19
 The existence of insect pollination dates back to the dinosaur era.
 In zoophily, pollination is performed by vertebrates such as birds and
bats, particularly, hummingbirds, sunbirds, spiderhunters,
honeyeaters, and fruit bats.
 Ornithophily or bird pollination is the pollination of flowering plants
by birds.
 Chiropterophily or bat pollination is the pollination of flowering
plants by bats.
 Plants adapted to use bats or moths as pollinators typically have
white petals, strong scent and flower at night, whereas plants that
use birds as pollinators tend to produce copious nectar and have red
petals.
 Insect pollinators such as honey bees (Apismellifera), bumblebees
(Bombusterrestris), and butterflies (Thymelicusflavus) have been

Page 9 of 19
 observed to engage in flower constancy, which means they are more
likely to transfer pollen to other conspecific plants.
 This can be beneficial for the pollinators, as flower constancy
prevents the loss of pollen during interspecific flights and pollinators
from clogging stigmas with pollen of other flower species.
 It also improves the probability that the pollinator will find
productive flowers easily accessible and recognizable by familiar
clues.

MECHANISM
 Pollination can be accomplished by cross-pollination or by self-
pollination:
 Cross-pollination, also called allogamy, occurs when pollen is
delivered from the stamen of one flower to the stigma of a flower on
another plant of the same species.
 Plants adapted for cross-pollination have several mechanisms to
prevent self-pollination; the reproductive organs may be arranged in
such a way that self-fertilisation is unlikely, or the stamens and
carpels may mature at different times.

Modes of Cross Pollination:

 The agencies which transfer pollen grains from anthers of one flower
to the stigma of different flowers are as follows: WIND
(Anemophily), WATER (Hydrophily), INSECTS (Entomophily), BIRDS
(Ornithophily)' and BATS (Chiropterophily).

Page 10 of 19
(1) Anemophily:
• Anemophilous plants produce enormous amount of. Pollen grains: A
single plant of Mercurialis annually has been estimated to produce
1,352,000,000 pollen grains.
• Anemophilous plants bear small and inconspicuous flower. The
pollen grains are small, light, smooth and dry.
• Pollen of some plants are said to be blown to 1,300 km. In some
plants as Pinus, pollen grains are winged.
• The flowers are usually unisexual in some plants e.g. Mulberry is
borne in independent catkins which can sway freely and shake off
their pollen in air.
• The flowers may be borne on long axis (as in grasses) much above
the leaves.
• The anther is versatile so as to oscillate in all directions at the tip of
filament.
• In Urticaceae filaments are very long.
• Anempohilous flowers have adequate devices to catch the air-borne-
pollen grains with utmost efficiency. For this the stigma is usually
large and feathery (as in grasses) and brush like as in Typha.

(2) Hydrophily:
 It is of two types:
o Hypohydrogamy: Includes plants which are pollinated inside
the water, e.g. Ceratophyllum, Najas.
o Epihydrogamy: Vallisneriaspiralis (ribbon weed) is a submerged
dioecious plant.
 The flowers are borne under water.
 When mature, the male flower get detached from the
parent plant and float on the surface of water.

Page 11 of 19
  The pistillate flowers also develop under water, at the
time of pollination; they are brought to the surface by
their long and slender stalks.
 As it arrives on the surface it forms a cuplike depression.
 If male flowers floating on water get lodged into the
depression, the pollination takes place.
 After pollination, the stalk of the pistillate flower
undergoes spiral torsion bringing the pollinated flower
under water once more.

(3) Entomophily:
 Some of the insects which help in pollination are bees, flies, wasps,
moths and beetles.
 Bees, flies and beetles visit flowers which open after sunset. Bees
probably carry out 80% of all pollination done by insects.
 Bee pollinated flowers are colored, possess special smell and/or
produce nectar.
 Pollen grains are sticky or with spinousexine.
 Also, the stigma is sticky and bees are color blind for red.

(4) Ornithophily:
 Tiny birds like humming birds and honey thrushes (hardly 1 inch
long) feeds on the nectar of flower like Bignonia, Erythrina is visited
by crows.

(5) Chiropteriphily:
 Bauhinia megalandra of Java and Anthocephalus are pollinated by
bats.

Page 12 of 19
(6) Malcophily:
 Many aroids which are usually pollinated by Diptera are also
pollinated by snails.

Mechanism of Self Pollination

 Self-pollination occurs when pollen from one flower pollinates the
same flower or other flowers of the same individual.
 It is thought to have evolved under conditions when pollinators were
not reliable vectors for pollen transport, and is most often seen in
short-lived annual species and plants that colonize new locations.
 Self-pollination may include autogamy, where pollen is transferred
to the female part of the same flower; or geitonogamy, when pollen
is transferred to another flower on the same plant.
 Plants adapted to self-fertilize often have similar stamen and carpel
lengths.
 Plants that can pollinate themselves and produce viable offspring are
called self-fertile.
 Plants that cannot fertilize themselves are called self-sterile, a
condition which mandates cross-pollination for the production of
offspring.

Cleistogamy
 It is self-pollination that occurs before the flower opens.
 The pollen is released from the anther within the flower or the
pollen on the anther grows a tube down the style to the ovules.
 It is a type of sexual breeding, in contrast to asexual systems such as
apomixis.
 Some cleistogamous flowers never open, in contrast to
chasmogamous flowers that open and are then pollinated.

Page 13 of 19
 Cleistogamous flowers are by necessity found on self-compatible or
self-fertile plants.
 Although certain orchids and grasses are entirely cleistogamous,
other plants resort to this strategy under adverse conditions.
 Often there may be a mixture of both cleistogamous and
chasmogamous flowers, sometimes on different parts of the plant
and sometimes in mixed inflorescences.
 The ground bean produces cleistogamous flowers below ground, and
mixed cleistogamous and chasmogamous flowers above.

POLLEN VECTORS
 Biotic pollen vectors are animals, usually insects, but also reptiles,
birds, mammals, and sundry others, that routinely transport pollen
and play a role in pollination.
 This is usually as a result of their activities when visiting plants for
feeding, breeding or shelter.
 The pollen adheres to the vector's body parts such as face, legs,
mouthparts, hair, feathers, and moist spots; depending on the
particular vector. Such transport is vital to the pollination of many
plant species.

Page 14 of 19
 Any kind of animal that often visits or encounters flowers is likely to
be a pollen vector to some extent.
 For example, a crab spider that stops at one flower for a time and
then moves on might carry pollen incidentally, but most pollen
vectors of significant interest are those that routinely visit the
flowers for some functional activity.
 They might feed on pollen, or plant organs, or on plant secretions
such as nectar, and carry out acts of pollination on the way. Many
plants bear flowers that favor certain types of pollinator over all
others.
 This need not always be an effective strategy, because some flowers
that are of such a shape that they favor pollinators that pass by their
anthers and stigmata on the way to the nectar, may get robbed by
ants that are small enough to bypass the normal channels, or by
short-tongued bees that bite through the bases of deep corolla tubes
to extract nectar at the end opposite to the anthers and stigma.

 Some pollinator species can show huge variation in pollination

effectiveness because their ability to carry pollen is impacted by
some morphological trait.
 This is the case in the white-lined sphinx moth, in which short-
tongued morphs collect pollen on their heads but long-tongued
morphs do not carry any pollen.
 Some flowers have specialized mechanisms to trap pollinators to
increase effectiveness. Other flowers will attract pollinators by odor.
 For example, bee species such as Euglossacordata are attracted to
orchids this way, and it has been suggested that the bees will

Page 15 of 19
 become intoxicated during these visits to the orchid flowers, which
last up to 90 minutes.
 However, in general, plants that rely on pollen vectors tend to be
adapted to their particular type of vector, for example day-pollinated
species tend to be brightly colored, but if they are pollinated largely
by birds or specialist mammals, they tend to be larger and have
larger nectar rewards than species that are strictly insect-pollinated.
 They also tend to spread their rewards over longer periods, having
long flowering seasons; their specialist pollinators would be likely to
starve if the pollination season were too short.

Page 16 of 19
 OBSERVATION

--- specific pollination commonly found in Punjab

agricultural field

• Honeybees
• Bumblebees
• Butterflies
• Native moths
• Beetles

--- Crops most dependent on insect pollination

• Mustard
• fruits like citrus and mangoes
• vegetable like cucumbers and tomatoes

--- Does traditional farming practices in Punjab support pollinator

population ?
• Traditional practices of them include diverse cropping and organic
methods with supports pollinators however be increased use of
chemicals fertilizers and pesticides in recent years has negatively
impacted pollinators.

--- If we talk about agriculture landscape of Punjab then we found out

that Punjab's monoculture farming practices limit plant diversity,
which reduces available food resources for pollinators . However,
Some farmers are starting to include wild flowers strips to support
pollinators.

--- does urbanization in India cities affect pollinator population ?

• urbanisation leads to have a loss of habitat which reducing food
resource for pollinators. However urban gardens and parks can create
Micro habitat that support for support species.

Page 17
--- For supporting pollinators health our Indian government policies
are also nowadays focusing and taking initiative steps like the
national pollinator mission focus on research and conservation
strategies to protect pollinators and promote sustainable agriculture
And raise public awareness.

Page 18
 CONCLUSIONS

 Pollination management is a branch of agriculture that seeks

to protect and enhance present pollinators and often
involves the culture and addition of pollinators in
monoculture situations, such as commercial fruit orchards.
 The largest managed pollination event in the world is in
Californian almond orchards, where nearly half (about one
million hives) of the US honey bees are trucked to the
almond orchards each spring.
 New York's apple crop requires about 30,000 hives; Maine's
blueberry crop uses about 50,000 hives each year.
 Bees are also brought to commercial plantings of cucumbers,
squash, melons, strawberries, and many other crops. Honey
bees are not the only managed pollinators: a few other
species of bees are also raised as pollinators.
 The alfalfa leafcutter bee is an important pollinator for alfalfa
seed in western United States and Canada.
 Bumblebees are increasingly raised and used extensively for
greenhouse tomatoes and other crops.

 The ecological and financial importance of natural pollination

by insects to agricultural crops, improving their quality and
quantity, becomes more and more appreciated and has given
rise to new financial opportunities.
Pag 19 f 19
 The vicinity of a forest or wild grasslands with native
pollinators near agricultural crops, such as apples, almonds
or coffee can improve their yield by about 20%.

 The benefits of native pollinators may result in forest owners

demanding payment for their contribution in the improved
crop results – a simple example of the economic value of
ecological services.

 Farmers can also raise native crops in order to promote

native bee pollinator species as shown with L. vierecki in
Delaware and L. leucozonium in southwest Virginia.

Pag 20
 BIBLOGRAPHY

Biological Science: Third Edition By, N. P. O. Green

(Author), G. W. Stout (Author), D. J. Taylor
(Author), R. Soper (Editor)
Exploring Biology By, Ella Thea Smith
NCERT Text Book
Encyclopedia Britannica
www.wikipedia.com

Pag 21