What is Pollination?

ollination is the act of transferring pollen grains from the male anther of a
flower to the female stigma. The goal of every living organism, including
plants, is to create offspring for the next generation. One of the ways that
plants can produce offspring is by making seeds. Seeds contain the genetic
information to produce a new plant.

Flowers are the tools that plants use to make their seeds. The basic parts of
the flower are shown in the diagram below.

Seeds can only be produced when pollen is transferred between flowers of

the same species. A species is defined a population of individuals capable of
interbreeding freely with one another but because of geographic,
reproductive, or other barriers, they do not interbreed with members of other
species.

Pollination is usually the unintended consequence of an animal’s activity on a

flower. The pollinator is often eating or collecting pollen for its protein and other
nutritional characteristics or it is sipping nectar from the flower when pollen grains
attach themselves to the animal’s body. When the animal visits another flower for
the same reason, pollen can fall off onto the flower’s stigma and may result in
successful reproduction of the flower.

Plants can be:

 Self-pollinating - the plant can fertilize itself; or,

 Cross-pollinating - the plant needs a vector (a pollinator or the wind)
to get the pollen to another flower of the same species.
Self-Pollination
Self-pollination occurs whenever pollen is transported from the anthers of a flower to the
stigma of the same bloom. The Hermaphrodite or dioecious plants are types of plants,
which have both male and female sexual components on the same flower, frequently
use this method of pollination.
And there is less reliance on external stimuli to trigger pollination in self-pollinating
plants. Wind or other tiny insects that visit the bloom on a frequent basis are necessary
for these plants to survive. The anthers and stigma of self-pollinating flowers are of
comparable lengths to aid pollen transport. Self-pollination is further subdivided into two
categories:
Autogamy
Autogamy is a form of self fertilization where fusion of two gametes from the
same individual take place. It is most commonly observed in the form of self-
pollination.
 Autogamy is generally avoided in nature as the seeds produced result
in subsequent species with low genetic diversity.
 This type of pollination can be seen in wheat, rice, pea, and other
crops.

As it is said that pollen is transmitted from the anthers of one flower to the stigma of
another flower in this sort of self-pollination.
Anthers are transmitted from the anthers of one bloom to the stigma of another flower
on the similar plant in this sort of self-pollination.
Geitonogamy

Geitonogamy is a type of self-pollination that involves the transfer of pollen

grains from the anther of one flower to the stigma of another flower on the
same plant.
 Functionally it is similar to cross-pollination, but genetically similar to
autogamy.
 It requires pollinating agents, such as wind, insects,birds,etc. A
pollinator can visit multiple flowers on the same plant to complete the
process of pollination.
 Examples: Monoecious plants like maize.
Advantages of Self- Pollination
Self pollination have several advantages that includes:
 Self-pollination preserves the genetic properties of a species.
 Plants need not depend on the external pollinating agents like wind,
insects or birds for pollination.
 Self-pollination ensures seed production.
 There are fewer chances of pollination failure.
 Self-pollination avoids pollen grain wastage.
 Flowers don't need to produce scent, nectar, or be colored to attract
pollinators.
Disadvantages of Self-Pollination
Some of the disadvantages of self-pollination are as follows:
 Seeds are produced in small quantity and are of low quality.
 Self-pollination can lead to a lack of variation, which means there is no
adaptation to changing environments or potential pathogen attacks.
 It prevents the creation of new plant varieties.
 Self-pollination doesn't introduce new characteristics, which can
decrease the immunity of the offspring.
 It doesn't allow weaker strains to be eliminated.
Cross Pollination
Cross Pollination is a process that occurs when pollen from one flower is
transferred to the pistils of another flower. This occurs between flowers on
different plants of the same species. Unlike self-pollination, cross-
pollination involves the exchange of genetic material between different
individuals. Cross pollination requires pollinating agents like insects, bees,
birds,etc. Cross- pollination can be further divided into following types:
 Advantages And Disadvantages of Cross Pollination: Cross
pollination is the act of exchanging genetic material between
organisms of different species. The term is often used in agriculture,
and refers to the transfer of pollen from one plant to another plant
of a different variety or species. In horticultural terms, cross-
pollination is the transfer of pollen from the male part of a flower to
a female part of another flower. Pollen is extremely light and can
travel on the wind, so it’s very common for different plants to cross
pollinate.

Difference Between Self-Pollination and Cross-Pollination

Self-Pollination Cross-Pollination

Transfer pollen grains from the anther to the Transfer pollen grains from the anther to the
stigma of the same flower. stigma of a different flower.

This process can take place in the same This process can take place between two
flower or a different flower of the same plant. flowers present on different plants.

It occurs in the flowers which are genetically It occurs between flowers which are
identical. genetically different.

Few species that exhibit self-pollination Few species that exhibit cross-pollination –
– Paphiopedilum parishii, Arabidopsis apples, daffodils, pumpkins and grasses
thaliana

Causes homogenous conditions in Causes heterozygous condition in progenies.

progenies.
Self-pollination increases genetic uniformity Cross-pollination decreases genetic
and decreases genetic variation. uniformity and increases genetic variation.

Causes inbreeding. Causes outbreeding.

Reduces the gene pool. Maintains the gene pool.

Produces limited amounts of pollen grains. Produces large amounts of pollen grains.

In self-pollination, both the stigma and In cross-pollination, both the stigma and
anther simultaneously mature anther mature at different times.

Transfers a limited number of pollens. Transfers large numbers of pollen.

This process is carried out even when the For cross-pollination to happen, the flower
flowers are closed. should be open.

No need for pollinators to transfer pollen Require pollinators to transfer pollen grains.
grains.

Pollen grains are transferred directly to a Pollen grains are carried via wind, insects,
flower’s stigma. animals, water, etc.

Agents of Pollination:
The agents responsible for pollination in angiosperms have
been grouped into two main categories.

Agents of Pollination
Pollination is a fundamental process in plant reproduction, reliant on both biotic and abiotic
vectors. Each type of pollination agent plays a distinct role in facilitating the transfer of pollen
from the male anther to the female stigma, thus enabling fertilization.
Biotic Pollinators

1. Bees (Melittophily): Bees are primary pollinators for many flowering plants. They are
attracted to flowers by their color and scent and collect nectar and pollen, which they transfer to
other flowers, promoting cross-pollination. Examples of plants pollinated by bees include
Begonias.
2. Butterflies (Psychophily): Butterflies pollinate flowers as they feed on nectar. They are
drawn to brightly colored flowers and help in pollination by transferring pollen between flowers.
Orchids are commonly pollinated by butterflies.
3. Moths (Phalaenophily): Moths are nocturnal pollinators, attracted to flowers with strong
scents that are usually white or pale-colored to be visible at night. Plants like Datura are
pollinated by moths.

4. Flies (Myophily): Certain flowers emit odors that attract flies, which help in transferring
pollen. Flowers pollinated by flies, such as Primrose, often have strong, sometimes unpleasant
scents.
5. Beetles (Cantharophily): Beetles are attracted to flowers with strong odors and high nectar
content. They are significant pollinators for plants like Magnolias and Water Lilies.
6. Birds (Ornitophily): Birds, particularly hummingbirds, pollinate flowers as they feed on
nectar. They are attracted to brightly colored flowers with tubular shapes. Bird of Paradise is an
example of a plant pollinated by birds.
7. Bats (Chiropterophily): Bats pollinate large, often fragrant flowers that open at night. They
are essential for plants such as the Agave and African Baobab.
8. Carrion Flies (Sapromyophily): Carrion flies pollinate flowers that emit foul smells, such as
the Dead Horse Arum Lily. These flowers mimic the scent of rotting flesh to attract these flies.
Abiotic Pollinators

1. Wind (Anemophily): Wind pollination is common in many plants, especially those with
lightweight, non-sticky pollen grains that are easily carried by air currents. Plants such as
grasses and corn use wind for pollination, and their flowers often feature exposed stamens and
large, feathery stigmas.

2. Water (Hydrophily): Water pollination is relatively rare and primarily occurs in aquatic plants.
For instance, Vallisneria uses long stalks to reach the water surface for pollen release, while sea
grasses release pollen underwater. This method of pollination is more common among lower
plants like bryophytes.
3. Rain (Ombrophily): In regions with frequent rain, some plants use rain-splash for pollination.
This method helps in self-pollination when pollinators are scarce, providing a reproductive
assurance strategy under adverse conditions.
 Pollination in
Maize