Pollen–pistil interaction includes all the events from pollen deposition on stigma until

The pollen grain germinates on the stigma to produce a pollen tube through one of the germ pores. The contents of the pollen grain move into the pollen tube. Pollen tube grows through the tissues of the stigma and style and reaches the ovary. Pollen tube, after reaching the ovary, enters the ovule through the micropyle and then enters one of the synergids through the filiform apparatus. All these events from pollen deposition on the stigma until pollen tube enter the ovule are together referred to as pollen-pistil interaction.