Pollination and Its types with examples.Contrivances of self - Pollination and Cross - Pollination.Agents of Pollination is also clearly mentioned.The topic is clearly explained with relevant images for better understanding.

1. -Prepared By:
Sumita Sinha
(M.Sc-LS,B.Sc.B.Ed)

2. POLLINATION
LEARNING OBJECTIVES:
 To know about pollination.
 To develop understanding about the types of pollination.
 To make students aware about the contrivances of self -pollination and cross-
pollination.
 Identify the agents of pollination.

3. INDEX
1. Introduction
2. Types of pollination
A. Self pollination
• Contrivances for Self-Pollination
B. Cross pollination
• Contrivances for cross-Pollination
3. Agents of pollination

4. INTRODUCTION
 Pollen is a fine to coarse powdery substance
comprising pollen grains which are male
microgametophytes of seed plants, which produce
male gametes.
 Pollination is the transfer of pollen grains from the
anther of one flower to the stigma of the same or
another flower.
 later enabling fertilization and the production
of seeds.

5. TYPES OF POLLINATION

6. SELF-POLLINATION
1.Self Pollination-
The transfer of pollen from the anther of a
flower to the stigma of the same flower or
sometimes to that of a genetically identical
flower (as of the same plant or clone).
(a)Autogamy :
It is the kind of pollination in which the pollen
from the anthers of a flower is transferred to the
stigma of the same flower, e.g., wheat, rice,
pea, etc.
(b) Geitonogamy:
It is a kind of pollination where the pollen grains
from the anther of the flower are transferred to
the stigma of another flower borne on the same
plant but at different branches. It usually occurs
in plants, which show monoecious condition,
e.g., Cucurbita.

7. Contrivances for Self-
Pollination:
The major adaptations which favours self
pollination are;
(i) Bisexuality- Flowers should be bisexual
or hermaphrodite, e.g., Hibiscus etc.
(ii) Homogamy- In this method, both the
anthers and the stigma mature at the
same time, e.g., Mirabilis, Potato ,wheat
,Rice , etc.
(iii) Cleistogamy- In some plants, flowers
never open up and the anthers dehisce
inside these closed flowers to ensure
pollination. Thus, cleistogamous flowers
are invariably autogamous as there is no
chance of cross-pollination. These
flowers produce assured seed sets even
in the absence of pollinators, e.g., Oxalis,
Viola, etc.
Viola
Homogamy

8. CROSS-POLLINATION
2.Xeno-gamy (Cross-Pollination):
It involves the transfer of pollen grains
from the flower of one plant to the
stigma of the flower of another plant.
This is the only type of pollination which
brings genetically different types of
pollen grains to the stigma during
pollination, e.g., papaya, maize, etc.

9. Contrivances for Cross-Pollination :
Nature favours cross- pollination. All unisexual flowers and
a large majority of bisexual flowers are naturally cross-
pollinated.
(i) Diclincy or unisexuality:
Cross-pollination is the rule among diclinous plants, i.e.,
those bearing unisexual flowers. In dioecious(male and
female flower borne on different plants) plants nothing else
can take place. In monoecious plants (male and female
flower borne on same plant) the only alternative is
geitonogamy which, however, has the same effect as self-
pollination.
(ii) Self-sterility or Incompatibility:
When pollen grain of an anther do not germinate on the
stigma of the same flower or a flower of the same strain of
plants. In some orchids, flowers wither away if pollinated
by its own pollen.
Many species of Solanum (potato, tobacco, etc.) and the
tea plant are self-sterile because of genetic reasons. Cross-
Cucurbita-zucchini

10. (iii) Dichogamy:
When stamens and carpels of a bisexual flower mature at
different times, pollination between them becomes ineffective.
Sometimes, however, it is found that self-pollination may take
place at a later stage if cross-pollination fails. Dichogamy may
be of two types:
-Protandry:
The anthers ripen first as in most Compositae , many
Umbelliferae, Malvaceae, etc. As a result, when the anther
bursts, it pollinates stigmas of other flowers but not its own
stigma which is not yet ripe.
-Protogyny:
The carpel matures first as in many members of Annonaceae
(e.g., Annona, Polyalthia)and Magnoliaceae (e.g., Magnolia,
Michelia) as well as in Arum maculatum. When the stigma is
receptive, its own pollen is riot ripe so that it has to depend on
foreign pollens.
Altomata procumbens protogyny
Aeonium Protandry

11. 4. Herkogamy (herkos = barrier):
In some flowers there may be some physical barrier
between the anther and the style so that pollination between
them is rendered difficult or even impossible.
 The male and female sex organs lie at some distance
from each other.
 In some flowers corolla has peculiar forms which act as
barrier in self pollination.e.g.,Aristolochia.
 In some other flowers, the pollen are held together to
form pollinia which can only be carried away by insects.
e.g., Orchids and Calotropis.
5. Heteromorphism:
In certain plants there are flowers of two (dimorphic) or
three (trimorphic) different forms with anthers and stigmas
at different levels. This dimorphism or trimorphism usually
involves heterostyly (styles of different lengths) and
heteroanthy (i.e., different types of anthers).Thus facilitate
cross pollination.
 Some of them posses a long style but short stamens
and are known as pin-eyed while other have short style
and long stamens. These are known as thrum-eyed.e.g.,
Herkogamy

12. AGENTS OF POLLINATION
Agents of
pollination
Abiotic
Agents
Wind
Water
Rain
Biotic
Agents
Insects
Mammals
Reptiles
Birds

13. ABIOTIC AGENTS
 Non living methods
 Energy spent on pollen not on attracting pollinators
1. By wind : Anemophily
 98% of abiotic pollination
 Arose due to changes in environment and availability of
pollinators
 Plant characteristics-
 specific height.
 Flowers are small, colourless, inconspicuous, nectar less and
become arranged as inflorescence.
 The stigmas are large, hairy and feathery or branched to catch
the air borne pollen grains.
 The anthers are well exposed for the easy dispersal of pollen
grains.
 Pollen grains are small, light, dry, dusty, non-sticky and
sometimes even winged.
Dandelions

14. 2.By water: Hydrophily
 Rare, limited to 30 genera, mostly monocotyledons
 Uses water to transport pollen or whole anthers
 Plant characteristics-
 Flowers are small, colourless, inconspicuous, odourless
and nectar-less and pollen grains and stigmas are
generally unwettable(algae, bryophytes and
pteridophytes).
 In Vallisneria, the female flower reach the surface of
water- stigmas are long and sticky and pollen grains
released- on surface of water- carried by the passive
water currents
 In a majority of aquatic plants, the flowers emerge above
the level of water and are pollinated by insects or winds
as in land plants, e.g., water hyacinth and lily
 Other examples -Hydrilla and Zostera
Vallisneria

15. 3.By rain:
 Used by small % of plants.
 Heavy rain discourages insect pollination and
damage unprotected flowers.
 Mechanism- suitably adapted plants, such
as Ranunculus flammula and Caltha palustris-
excess rain drains allowing the floating pollen to
come in contact with the stigma.
 In rain pollination- orchid Acampe rigida, the rain
allows for the anther cap to be removed, allowing for
the pollen to be exposed. After exposure, raindrops
causes the pollen to be shot upward, when the stipe
pulls them back, and then fall into the cavity of the
stigma. This allows the plant to self-pollinate, which
is useful when biotic pollinators in the environment
have decreased.
Acampe rigida

16. BIOTIC AGENTS
o Pollination involves pollinators/pollen vectors
o 100,000-200,000 species of animals act as pollinators
1. By insects: Entamophily
 Major pollinating agent
 insects such as, bees, wasps and occasionally ants
 Plant characteristics-Insect-
 pollinated flowers are large, colourful, fragrant, conspicuous
and rich in nectar.
 The pollen grains and stigmas are sticky.
 Nectar + pollen grains = floral rewards insect pollinators.
 In some species, floral rewards = safe place to lay eggs,
e.g., for the tallest flower of Amorphophallus (about 6 feet in
height).
 In plant Yucca, moth and the plant, cannot complete their
life cycles without each other. The moth deposits its eggs in
the locule of the ovary and the flower, in turn plant gets
pollinated by the moth.
Yucca

17. 2.By vertebrates: zoophily
 pollination is performed by vertebrates such
as birds and bats,
particularly, hummingbirds, sunbirds, spiderhunters,
honeyeaters, and fruit bats.
 Birds-ornithophily- prefer plant with copious nector rich
in carbohydrate and red petals.
 Bats-chiropterophily- prefer plants with white petals,
strong scent and flower at night
 Reptiles- found in island system; predator pressure-
reptiles become herbivorous- eat nector and pollen; e.g.
Podarcis lilfordi
 Mammals- some rodents, bats and marsupials-The
flowers are borne near the ground, are yeasty smelling,
not colourful, and sunbirds reject the nectar with its
high xylose content. The mice apparently can digest the
xylose and they eat large quantities of the pollen.