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Fig. 1. Simplified model of genetic control of floral initiation in the quantitative long day plant Arabidopsis thaliana, based on Koornneef et al. (1998). Floral meristem development is considered to be autonomous or automatic unless repressed by floral repression (vegetative) genes. Genes known to be involved in photoperiodic control of flowering produce a permissive signal that blocks the vegetative genes, thus derepressing the floral meristem identity genes. This model was simplified by omission of the constitutive pathway, which reinforces the vegetative gene action, and the vernalization pathway, with the associated gibberellin subpathway, which represses the vegetative genes.
