Many plant physiologists and chemists attempted to isolate and characterize florigen using various methods. In many studies, plants were homogenized and the extracts were bioassayed for flower-inducing activity. Many known substances including plant hormones were also bioassayed, and changes in their endogenous levels were examined during the transition to flowering. Unknown substances extracted from plants have been physiocochemically analyzed. The pursuit to find specific gene expression under an inductive condition is also ongoing.
　 The detection of biological activity by bioassay is the most general method, and many reports have been published. However, clear and reproducible results have not been obtained.