Some long-day plants like Arabidopsis thaliana form a rosette in their vegetative state, namely they produce many leaves around a very short stem. The first sign of flowering for these rosette-forming plants is bolting, that is, elongation of stems. A mutant, embryonic flower (emf), has been isolated from A. thaliana. The emf mutant flowers without a rosette stage, namely it flowers immediately after the cotyledons have expanded. The EMF gene corresponding to emf mutation functions as a flower-suppressing gene inhibiting the transition of a vegetative shoot apex to a reproductive one. The activity of the EMF gene may decrease gradually during the plant ontogeny or its expression may be suppressed by other flower-promoting genes resulting in flowering.
　　Another important mutant is leafy (lfy) which bolts but does not form flowers. The shoot apical meristem of lfy changes to an an inflorescence meristem, but the inflorescence meristem does not change to a flower meristem. Therefore, it produces a leaf-like structure at the position where flowers should have been produced. The product of the LFY gene may have a role in transcription. Flowering is promoted in A. thaliana plants over-expressing the LFY gene. Over-expression of the LFY gene in poplar plants and some other plant species has resulted in precocious flowering. These results indicate that the LFY gene plays an important role in the regulation of flowering.

　　Many mutants showing delayed or hastened flowering time have been isolated from A. thaliana. Among the corresponding genes cloned, CONSTANS (CO) and FLOWERING TIME (FT) which are flower-promoting genes are considered to be the most important. The product of the CO gene is a transcriptional factor. Over-expression of the CO gene promoted flowering, and induced the expression of the LFY gene. Many other genes have been cloned and interactions between those genes have been analyzed. The system regulating flowering by genes was schematically postulated, and a lot of models have been reported.
　　A late-flowering mutant, indeterminate 1 (id1) was isolated in Zea mays, and ID1 gene was cloned. The ID1 gene was expressed only in immature leaves. This fact suggests that the ID1 protein may be involved in the generation of a transmissible flowering stimulus, or ID1 protein itself may function as a flowering stimulus. This supports the florigen concept.