Pollen-pistil interaction involves
Pollen deposition on stigma
Rejection or acceptance of pollen by stigma
Entry of pollen tube into ovule
All of these
All the events from pollen deposition on the stigma until the entry of the pollen tube into the ovule are together referred to as pollen-pistil interaction.
The length of the pollen tube depends on the distance between : (a) pollen grain and the upper surface of the stigma (b) pollen grain on the upper surface of stigma and ovule (c) pollen grain in anther and the upper surface of the stigma (d) the upper surface of stigma and lower part of the style
The acceptance or rejection of pollen is based on the biochemical interaction between the components of the pollen wall and pistil head.