The document discusses pollen-pistil interaction, detailing the sequence of events from pollen deposition to fertilization, including concepts of sexual compatibility and incompatibility. It defines self-incompatibility, its genetic control, and types such as heteromorphic and homomorphic incompatibility, as well as their mechanisms. Additionally, it explores methods for overcoming incompatibility, emphasizing the importance of self-incompatibility in maintaining genetic diversity and plant vigor.

1. POLLEN –PISTIL INTERACTION
KAKATIYA GOVERNMENT COLLEGE, HANAMKONDA
WARANGAL(URBAN) DIST. TELANGANA STATE
DEPARTMENT OF BOTANY
Prepared by
Dr. T. Annie Sheron
Assistant Professor of Botany

2. Structure of Anther
Pollen-pistil interaction is a sequence of events that occur
from the time of pollen deposition over the stigma till the time
of entry of pollen tube inside the ovule

3. & embryo sac
Double Fertilization
Step wise events in
Pollen Pistil Interaction
https://www.youtube.com/watch?v=WdCCGQOkyG0
Sugary substance secretion by stigma

4. Sexual compatibility –
→Pistil (gynoecium) has certain devices to recognize the right
kind of pollen and allow it to germinate and discard the
unwanted pollen.
→Fertile pollen which brings about fertilization is called
compatible pollen.
Sexual incompatibility
→ Pistil is not able to set seed or fertilize
even after pollination with viable and
fertile pollen then it is considered to
be incompatible.
→ May be interspecific or intraspecific
(Self sterility or Self incompatibility)

5. Self Incompatibility
‘the inability of the plant producing functional male and female
gametes to set the seed after self-pollination’.
Genetically it is under the control of a single gene locus called
Sterility locus (S) with multiple alleles.
During pollination, if the pollen grains and the stigma have the
same allele then they remain incompatible.

6. Self incompatibility types:
1. Heteromorphic incompatibility
‘Production of more than one morphological type of
flowers within the species’.
Flowers differ either in structure or in arrangement of
androecium and gynoecium (distyly/tristyly) at different
heights.
Distyly, 2 kinds of flowers-
long styled-short stamens (pin
morph) and short styled-long
stamens (thrum morph).
Controlled by single gene complex S with two
alleles S (Short Style) and s (Long Style).

7. 2. Homomorphic incompatibility
‘Production of morphologically similar flowers by different
plants but they are physiologically different’.
Barriers are located either on stigma or in the style to stop
germination.
Incompatibility may be due to the genotype of the plant on which
it is produced (sporophytic control) or by its own genotype
(gametophytic control).

8. Types of Homomorphic incompatibility
1.Gametophytic Self- incompatibility (GSI)
The inability of the gametes from the same parent plant to fuse
and form a zygote or, if the zygote forms, then it fails to
develop.
The incompatibility resides on the genotype of the pollen grain
Solanaceae, Papavaraceae, Rosaceae, Rubiaceae, Liliaceae etc.
In pollen meiocytes, the S-gene
activation is delayed till the
completion of meiosis.
Growth of the pollen tube arrests
in the style

9. 2. Sporophytic Self- incompatibility (SSI)
The secretions of the stigmatic tissue or the transmitting tissue
prevent the germination or growth of incompatible pollen.
 The pollen is shed in 3-celled stage & S-gene activation is
completed before the meiosis
Asteraceae, Brassicaceae, Convolvulaceae etc.
Zone of incompatibility is the
stigma i.e, the pollen either fail to
germinate or the pollen tube fail to
penetrate the stigma

10. Methods to overcome Incompatibility
1. Pollination methods
2. Irradiation method
3. Heat treatment of style
4. Chemical treatment:
5. Parasexual hybridization

11. 1. Pollination methods
Mixed pollination
Stigma is coated with a mixture of live incompatible pollen and killed
compatible pollen so that proteins from the killed compatible pollen
will mask the inhibition reaction.
Ex: Cucumis, Nicotiana, Cosmos
Bud pollination
self pollination is done in the bud stage (2 days prior to anthesis) as
the incompatibility factor lies in the style
Ex: Petunia axillaris
Stub pollination
Removing stigma and a part of style and direct dusting of pollen on
the cut/stub surface Ex: Ipomea trichocarpa

12. Intra ovarian pollination
Incompatibility lies in stigma or in style. direct introduction of pollen
suspension into the ovary brings about pollination.
Ex: Argemone Mexicana, Papaver somniferum
Test tube pollination:
Ovules and pollen are grown in nutrient medium side by side and as
the pollen germinate, the pollen tube find their way to the ovule to
fertilize. Ex: Papaver somniferum

13. Importance of self incompatibility
-Helps in maintaining heterozygosity and helps in evolving
new varieties which can survive in adverse conditions.
-- Prevents excessive self pollination, which over a period of
time leads to loss of vigor.