Pollen–Pistil Interaction

Introduction

After pollination, pollen grains land on the stigma of a flower. But every pollen grain may not be suitable for fertilization.

The pistil has the ability to identify whether the pollen grain is:

• Compatible (right type)   or

• Incompatible (wrong type)

This process is called Pollen–Pistil Interaction.

What is Pollen–Pistil Interaction?

Pollen–pistil interaction is the series of events from:

• deposition of pollen on stigma to entry of pollen tube into the ovule.

It includes:

• Recognition of pollen

• Acceptance or rejection of pollen

• Growth of pollen tube

• Entry into ovule

Compatible and Incompatible Pollen

Compatible Pollen

Compatible pollen is pollen from the same species that can successfully fertilize the ovule.

Result

• Pollen germinates

• Pollen tube grows

• Fertilization occurs

Example

Pollen of Pea on another pea flower.

Incompatible Pollen

Incompatible pollen may come:

• From another species   OR

• From the same plant in self-incompatible plants

Result

• Pollen germination is prevented   OR

• Pollen tube growth stops

Example

Pollen of Mustard rejected by its own stigma in self-incompatible varieties.

Recognition of Pollen by Pistil

The pistil recognizes pollen through chemical interaction between:

• pollen grains and

• pistil tissues

This chemical communication helps the pistil decide whether to:

• accept pollen OR

• reject pollen

Steps of Pollen–Pistil Interaction

1. Pollination

Pollen grains are deposited on the stigma.

Diagram

Anther →→→ Stigma (Pollen transfer)

2. Pollen Germination

If pollen is compatible, it germinates on the stigma through a germ pore and forms a pollen tube.

Diagram

     Pollen grain
          ●
         / \
        /   \
     Pollen tube

Example

Pollen germination can be observed in:

• Pea

• Chickpea

• Balsam

• Vinca

3. Growth of Pollen Tube

The pollen tube grows through:

• stigma

• style

• ovary

to reach the ovule.

Diagram

 Stigma
    |
    |
  Style
    |
    |
  Ovary
    |
  Ovule

(Pollen tube grows downward)

4. Formation of Male Gametes

In Two-Celled Pollen

Pollen grain contains:

• One vegetative cell

• One generative cell

During pollen tube growth, the generative cell divides to form:

• Two male gametes

In Three-Celled Pollen

Pollen already contains:

• One vegetative cell

• Two male gametes

So pollen tube carries the male gametes from the beginning.

5. Entry into Ovule

The pollen tube enters:

• Ovule through micropyle

• One synergid through filiform apparatus

Role of Filiform Apparatus

It guides the pollen tube into the embryo sac.

Diagram

        Ovule
      __________
     |          |
Micropyle →  Pollen tube
     |          |
     | Synergid |
     |__________|

Importance of Pollen–Pistil Interaction

• Ensures correct fertilization

• Prevents wrong pollination

• Helps in hybrid formation

• Important in plant breeding

Artificial Hybridisation

Artificial hybridisation is a technique used by plant breeders to produce plants with desirable characters.

Example

Developing disease-resistant or high-yielding crops.

Techniques Used in Artificial Hybridisation

1. Emasculation

Removal of anthers from bisexual flower buds before anther dehiscence.

Purpose

Prevents self-pollination.

Diagram

Flower bud
   ↓
Removal of anthers
(using forceps)

Example

Used in hybridization of:

• Pea

• Hibiscus

2. Bagging

After emasculation, flowers are covered with butter paper bags.

Purpose

Prevents unwanted pollen contamination.

Diagram

   Flower
     ↓
 [Covered with bag]

When stigma becomes receptive:

• Desired pollen is dusted

• Flower is rebagged

Artificial Hybridisation in Unisexual Flowers

In unisexual flowers:

• Emasculation is not required

• Female flowers are directly bagged before opening

Example

• Maize

• Papaya

Simple Summary Table

Process	Function
Pollen recognition	Identifies compatible pollen
Pollen germination	Produces pollen tube
Pollen tube growth	Carries male gametes
Emasculation	Prevents self-pollination
Bagging	Prevents unwanted pollination

    

           Pollen–pistil interaction is a very important process in flowering plants. It helps the pistil recognize the correct pollen and ensures successful fertilization. Knowledge of this process is very useful in plant breeding and artificial hybridisation for developing improved crop varieties.