Pollen grains are deposited on the stigma either due to closeness of anther to stigma or by pollinating agents.

1. Pollen attachment and hydration- it depends on stickiness of pollen.

2. Pollen germination and tube growth- enzymatic reactions occurs.

3. Path of pollen tube in style-  directional cell migration , canal cells secrete mucilagenous substances.

4. Path of pollen tube in ovule and embryo sac.

5.Recognition of pollen by stigma.

Significance of pollen pistil interactions- 

- most essential is screening of male gamete for the production of zygote.

- pollen are larger in number therefore face tough competitions. 

- direct relevance to breeding plants.