The florigen concept assumes one hormonal compound acting specifically to induce flowering. However, several compounds which are not specific to regulation of flowering can act as hormonal regulators.
　　In some plant species, endogenous levels of cytokinins, putrescine, sucrose and calcium ion increase and they move to the shoot apex under a flower-inducing condition. These facts suggest that flowering occurs when these compounds work together in the shoot apex. Therefore, all of these compounds could be factors necessary for the induction of flowering. This is called the multifactorial concept.
　　The florigen concept does not necessarily assume a single universal compound. It does not necessarily assume specific compounds. Florigen could be a mixture of two or more compounds, and they could be known compounds with multiple functions as usual plant hormones are. In this sense, the multifactorial concept may be considered as a variation of the florigen concept.

　　Any phenomena could occur either by supplying an inducer or by removing the inhibitor. It could be assumed that plants are basically in a vegetative state under the influence of a constitutively existing inhibitor of flowering and flower when the inhibitor has disappeared. The inhibitor may be deactivated or its biosynthesis may cease under an inductive photoperiodic condition. Supporting the presence of such an inhibitor, a long-day plant, Hyoscyamus niger flowers even under a short-day condition when all the vegetative leaves have been removed. This fact can be explained by assuming the removal of the inhibitor in the vegetative leaves. However, such an inhibitor has not been isolated.

　 　Information is transmitted throughout the plant body generally by the flow of chemical substances like plant hormones. The florigen concept stands on this principle. However, information can be transmitted even by electric signals as in the animal nerve system.
　　Tomato plants generate a protease inhibitor as a defense substance against insects when they are attacked by insects. Even healthy leaves which are positioned far from the attacked leaf generate the protease inhibitor within seconds. Such a quick systemic response can not be explained by assuming the flow of chemical substances. The information transmitted from the wounded leaf to other leaves was found to be an electric signal. A similar electric signal could be the information transmitted from the photoinduced leaf to shoot apex in the photoperiodic flowering. However, no evidence supporting this hypothesis has been reported so far.