IPA: //ˈflɔːrɪdʒən//
KK: /flɔˈrɪdʒən/
A substance in plants that helps them to produce flowers.
The presence of florigen in the plant triggered its blooming process.
Florigen is derived from "flor" (from Latin "florere", meaning to bloom or flower) and the suffix "-gen" (from Greek "genes", meaning born of or produced by). The word "florigen" refers to a substance that induces flowering in plants, thus meaning something that causes blooming.
Think of 'blooming' ('flor') and 'producing' ('-gen') to remember that 'florigen' is something that causes plants to flower.